Hello,
Is a 6.9 supposed to run over 100C when you drive it over 180 KMH for a while when the outside temperature is around 30C ?
I changed the Thermostat, Water pump , flushed the System multiple Times and recored the Radiator 2 times (1. standart core , 2.Perfomance core) but it didn't change anything .
Yesterday we had 35 and the Temp was always a little below 100C while drive slower then 120KM with air condition on.
The Radiator also had 100 C and ~ 85 on the Outlet so the coolant is flowing.
Today i checked the Headgasket with a cheap tester that changes color and it changes from blue to green , but i don't have any cooland loss , white smoke , or water in the oil.
Should a 6.9 under all cirumstances run below 100C ?
As is see everything speaks for a broken headgasket but i don't want to tear the engine apart and find out it wasn't the headgasket.
Greeting from germany
Ramiro
Quote from: ramiro on 26 July 2022, 10:20 AMHello,
Is a 6.9 supposed to run over 100C when you drive it over 180 KMH for a while when the outside temperature is around 30C ?
I changed the Thermostat, Water pump , flushed the System multiple Times and recored the Radiator 2 times (1. standart core , 2.Perfomance core) but it didn't change anything .
Yesterday we had 35 and the Temp was always a little below 100C while drive slower then 120KM with air condition on.
The Radiator also had 100 C and ~ 85 on the Outlet so the coolant is flowing.
Today i checked the Headgasket with a cheap tester that changes color and it changes from blue to green , but i don't have any cooland loss , white smoke , or water in the oil.
Should a 6.9 under all cirumstances run below 100C ?
As is see everything speaks for a broken headgasket but i don't want to tear the engine apart and find out it wasn't the headgasket.
Greeting from germany
Ramiro
I'm going to say "NO." Something is wrong, as you already suspect. My car had similar issues as yours, though maybe not quite as bad. As a reference, mine now runs in very low 90deg range with A/C on at similar speeds and 44deg outside (yes, that's hot! Summer in Las Vegas). No problems at all.
It was not always this way. I replaced thermostat and all hoses, flushed the block and had radiator flushed and descaled and flow tested. Problem gone. The radiator shop said flow was about 30% blocked with scale, kalk etc. For other I reasons I had the whole engine apart at the time. There was no visible scale build-up in the block. I had the heads had been boiled out too, so none of the coolant passages had any scale buildup either. So, after all that, I think my car is probably close to the ideal case.
In your case I don't see obvious head gasket issues. More likely, I think, is an obstruction someplace in the engine itself. I'm confident that substantial scale build-up could easily restrict flow enough to cause your problems. At 180kph and 43deg I'd guess I've driven close to the design limit and never over 100deg. Also, what does the temp do at low speeds and moderate temperatures? In any case, I'm not sure how you deal with severe scale in the block or heads. Obviously you could tear it apart and boil block and heads but that's an extreme measure. Can motor flushes achieve that same thing? I really don't know. Hopefully somebody else will comment. One thing you could to try is turning the heater on and seeing what happens. That won't be a fun test when it's 40deg outside. Keep us posted. Good luck and cheers,
44C and under 100 would be unbelievable for me , yesterday i had 98 also at low speed and idle when we had 35.
Do you have the euro radiator or the bigger us version without oil radiator ?
It also takes forever to go down to ~90 with slow driving when it reached ~115.
Blocked blocked would it not mean that the heat would not get transfered to the coolant and the engine would get hot in some places without the cooland overheating ,and if the coolant gets to hot the problem should be outside the engine or the engine makes too much heat?
I flushed the system with Acid several times over 2 years , and the coolant stays somewhat clear now and there are no rust pieces coming out, the radiator is also freshly recored so it should be clean.
Heater makes no real difference atleast at idle when i tried.
Dont forget the fan clutch. Remember that it is specific to the 6.9.
I assume the electric fan is working correctly. A quick hack to to add a 1.4K ohm resistor to the temp sensor to make the fan turn on sooner.
The Fan turns off over ~3000 RPM so at 180 it should not make any difference and under 3000 i can clearly hear it.
The Electrif fan also works fine but does not really make a difference i installed the bigger on from a w126.
Quote from: rumb on 26 July 2022, 01:17 PMDont forget the fan clutch. Remember that it is specific to the 6.9.
I assume the electric fan is working correctly. A quick hack to to add a 1.4K ohm resistor to the temp sensor to make the fan turn on sooner.
Thanks Robert, yes, I also changed clutch. My clutch was totally blown.
Ramiro:
My car is unmodified euro version. The radiator has transmission cooler only. Back to the problem. I think at this point I'd use an IR heat gun to carefully map the temperature of the engine to the extent possible. Why not? But honestly, I doubt that there would be substantial differences because the thermal conductivity of the engine is very high, so a small hot spot would be swamped out by heat transfer from adjacent areas.
Let's assuming that your clutch and fan are good. Let's also assume that the water pump is good (and that it's the right one, there are 2 styles). About all that's is a flow problem or a bad thermostat. I have seen bad thermostats and once I got a new one that was bad. Maybe recheck that again. Another thing I remembered - be sure that the A/C condensor is clear. Mine was
extremely clogged with bugs. They were hard to see and harder to remove. It seems like restricted air flow could cause your problems too.
Thermostats i tried 2 , also checked everyone in Boiling water and they were opening fine.
Also cleaned the A/C condensor because i had the same idea.
Last time i checked the Radiator with a ir heat gun directly after i turned the engine off and it had 100c like the cluster showed nearly all the way to the bottom , so i really doubt that i have a circulation problem.
try a new temp sender unit. rh head at the rear.
why , it shows the same temp like my ir gun also the electric fan kicks on when it shows 100 so i see no reason why its reading wrong .
This is reading more and more like head gasket but before you tear down the motor maybe get a 2nd opinion on the liquid test you performed. I am not sure how accurate these are but likely we have to assume that since you observed colour change exhaust gasses are present in the coolant.
You can also try a compression test on all cylinders, if you see really low values on 1 or more cylinders for sure your head gasket is toast.
Whilst you contemplate Daniel's reply, we are getting mixed messages.
In your first post you state :
The Radiator also had 100 C and ~ 85 on the Outlet so the coolant is flowing.
But then
]Last time i checked the Radiator with an ir heat gun directly after i turned the engine off and it had 100c like the cluster showed nearly all the way to the bottom , so i really doubt that i have a circulation problem.[/quote]
Unless you have 15 degrees+- between the top of the radiator and the bottom, you do have a circulation problem.!
The reason I suggested the sender unit was simply to eliminate it. That is after all what is causing the concern.......the gauge is reading a 100c and from my qik reading of it all, everything else you've measured with the IR says a 100 degrees. This seems a bit too coincidental. The top radiator hose after a 180 kph fling should be > 100c. That is, there is no measured temp differential anyway you test it. Everything is 100 degrees??
Something is not right. I'd be checking the accuracy of the IR gun...the validity of the temp sender...the differential in temp between top and bottom of the radiator (there should be a discernible difference..you should almost be able to touch the bottom hose. ]
To have a reading of 100c at the temp sender unit means other parts of the cooling system should be well in excess of that.
It just doesn't seem to be running hot, .its only the temp gauge that says its 10 degrees warmer than normal. Is that a fair assessment OR ...?
That values were after idle , after a fast drive it es exactly like you expect inlet ~110 and outlet ~ 95, temp gauge also showed 110 and everytime i meassured with a running engine its 15 degress difference, so it would be nice if the temp gauge would read high but i would it reading around +-2C precise.
Also when the engine got to 110 on the gauge it started pinging on part throttle at 160.
100 nearly all the way to the bottom was 1 minute after i turned the engine off after idling for some time the only way to check if the radiator is hot everywhere is with a non running engine because of the condenser thats why i meassured it like that.
I tried the test on 2 other cars first i got green on 1 but after cleaning the tester it stayed blue on both of them(so i am pretty sure it was contaminated still from 6.9), and after that i put it on the 6.9 again and it turned green again.
I did a compression test a year ago and 1 Cyl was down 1 bar but they were all 10 - 11 bar and the overheating is there since i first drove the car a year ago.
The leak kit you used seems to be verifying combustion gasses in the antifreeze. I read that some exhaust anylizers can dected anti freeze. Perhaps you could find a shop with such device.
I used this kit https://www.ebay.com/itm/175187507731 .
Quote from: ramiro on 27 July 2022, 08:10 AMI used this kit https://www.ebay.com/itm/175187507731 .
based on that it does indeed look like blown head gasket. And it makes sense. My remedies were based on the simple stuff that goes wrong most often. Perhaps time to start searching for head gaskets but unfortunately they aren't easy to find. You could try to classic center in California. They used to have a whole rebuild gasket kit that was reasonably priced. It included manifold and valve cover gasket. and many others.
Sadly thats also my conclusion but was hoping for a miracle.
As far as i saw the head gaskets kits ar available at mercedes for ~300 eur per side.
But i will still drive the car for a bit before i tear the engine apart , as long as its not over 30C(luckily not so often in germany) the engine temp is tolerable.
Don't give up yet!
You said you did a compression test about a year ago and one cyl was down about 1bar/14psi?
Do you remember which cyl it was?
Also on the matter of pinging. How is the timing of the engine? checkout OK?
I checked the timning also , it is fine pretty sure the pingin was because of the vacum advance and the high temp.
3 and 8 had around 10 the others had nearly 11 , but that was before driving .
I pressurized the coolant system and will look with a camera to maybe find some moisture in the cylinders hoping to confirm the head gasket problem.
ok...No 8 has a reputation for a slow leak across the head gasket to the back of the head.
So let's start there.
On a cold engine, remove no8 plug and look for any signs of moisture.
Is this plug noticeably lighter in colour?
Nothing untoward?
When you next take the beastie for a run, get it good n hot then remove No 8 and observe .
Still nothing?
While she is still warm put no 8 plug back in BUT disconnect the plug lead.
Disconnect no8 injector line and start her up. [you might want to collect the fuel ]
Give it a few revs etc ..let it run for a minute or so then remove plug no8 again.
What have we got?
I had all the Plugs out and pressured the system for multiple hours in the last days and there was no water in the cylinders when i checked with a endoscope.
After that i drove the car 50 and on the wayback i drive >= 180 for 3 km, before that temp was stable below 90 (20 outside) and after that went up to 98 and when i let off it was back to 90 after 2 km.
Weirdly the was no real pressure after that drive in the coolant system i was able to take the cap off while the engine was still running with out anything coming out.
While it was still running i made a test with the gasket tester and it turned slowly green after ~ 5 - 10 min.
So for it me it really seem like a super small headgasket leak but i don't understand why there was no real pressure i know that my new radiator cap is not 100 % sealed but it takes 1 hour to go from 1 bar to 0,3 when i pressurize the system and the car never pressed any fluid out the cap.
I am actually thinkin about putting a pressure gauge on the coolant system and check the pressure when i drive fast to see if it changes on load.
Weirdly the was no real pressure after that drive in the coolant system i was able to take the cap off while the engine was still running with out anything coming out.
I have extracted the above quote coz you are right...something weird is going on here??
When the system is hot and therefore pressurised, lifting the radiator cap from the reservoir should cause the fluid therein to expand in volume; such that when even mildly warm, the fluid could possibly overflow. When it is really hot [ as you have described ] you would have to exercise extreme care with the cap for fear of getting scalded by red hot fluid blowing out of the reservoir.
Yet as you have described it, nothing?
This raises the possibility that the radiator line to the reservoir is blocked. Is it possible that the top of the header tank is low?.ie it is low on coolant .
The reservoir looks full enuff coz it's blocked......you can't actually see what's going on in the radiator because it's a sealed system.
I don't wonder if this is the problem because the reservoir should be ebbing and flowing all the time...and blowing it's innards out when you release the cap after a good run.
Worthy of a look.
The Engine was not real hot at that time it had normal 90C so the coolant was not boiling , lines are not blocked and the radiator hoses were soft so not under pressure , i can only thing that the coolant expanded 98 C and when it cooled down to 90 it contracted so no pressure anymore.
I am just not understand i have a small headgasket leak were are the gases going when there is no pressure , when i putt the tester on i can see a small buble rising every ~20 seconds but i am not sure if thats air because the coolant is expanding when the engine heats up.
Edit:
Drove around with a pressure gauge attached to the coolant system and it only goes to ~ 0,3 and stays there also on full load and after i turn off the engine.
With engine fully warmed and the radiator cap removed, are there any bubbles of any size at any time interval in the reservoir? ie well after the coolant has expanded.
Similary, is there any measurable signs of fluid consumption.?..best measured after several cycles of getting hot..then cooling down..then getting hot etc with the CAP on. We are not looking for a lot here as clearly any possible leak is miniscule..so we measure it when it's cold compared with when it's cold...at least 5 cycles.
The Tester had a small bubble every 30 - 60 seconds but i am not sure if thats expansion because at idle the engine temp slowy creeps up to nearly 100C.
I drove the car ~ 10000 km with this problem and didnt notice any coolant loss but i always worked on the coolant system so i would max say without working on it was 2000 km.
...mmm interesting. So the car will overheat {indicated 100 degree] when left idling?
So it's not related to the rate of work that the engine is being called upon to do.
That is, at a 180 kph that donk is working hard and the temperature rises accordingly
[ to be expected but not to the degree that it indicates.]
At idle at 20deg C ambient temp, the temp should not indicate any more than 80-85.
Basically it overheats sitting still!!?
I feel there's a clue here.
1. Have we double checked the thermostat..............have we run the motor without the thermostat to see if it still overheats? See later point.
2. Viscous coupled fan. Does it feel free-ish when cold but binds when hot?
3. The fan belt is nice and snug?
4. bottom radiator hose to water pump....no blockage?
5. I think you have treble checked the radiator...core gets warm evenly from a cold start.....reflects a temp differential of about 15 degrees from header to bottom irrespective of whatever the temp gauge says?.
6 . Confirm that the aircon fan cuts in at 100 degrees.ie I presume it will cut in after a protracted idle with the aircon OFF ?
7. Are we getting full circulation in the cooling system?. ie confirm that the heater circuit is working.
If YES to all of the above, then our attention turns to the new water pump.
This may seem a little unorthodox.....Combine with Q1.
Disconnect the top radiator hose at the thermo housing. Remove the thermostat . Check as per Q1.
Start the engine....heater on...warm or cold....and observe the flow.it should be considerable and respond to engine rpm.
There will be enuff fluid in the radiator to last about a minute...ample time to determine that the water pump is delivering the goods. You can always place a hose down the throat of the top rad fitting to extend the test but you should get the picture pretty quick.
OK.after all of that, what have learnt?
Viscous coupled fan. Does it feel free-ish when cold but binds when hot?
6.9 dont work that way. They turn slower when hot.
.err think that one through again..?
@Rumb
Can you please elaborate?
What do you mean "slower when hot"?
Thanks
@Randys01
Well after i left it idling in the sun at 33C with Aircon on for 30 min it got to 98 .
1.Yes i tried a 80C thermostat and tested them both in hot water , no difference at all.
2.I am sure that its running because it's making more than enough noise
3.Yes
4.No whould the Radiator get hot if there would be a blockage ?
5.Yes
6.Yes it does
7.Yes its working very good
I now tried 2 Waterpumps the Sympthom are 100% identical , and one was badly coroded the other not, also why would the Radiator getting hot when i would have a circulation problem ?
@viscous fan
As far as is know the viscous always runs but turns down to 1200 rpm when the engine goes above 3500 rpm and mine does exactly that.
https://forum.w116.org/mechanicals/6-9-electric-cooling-fan/msg134432/#msg134432
reading the 100-985 manual
up to a speed of 3500 rpm the engine fan will run proportional to the engine speed, whereby a fan speed of 1900 rpm results
as engine speed increases further the fan speed will drop to about 1000 rpm and max of 1200
It should be very stiff when cold. if it freewheels at all it's shot.
Testing:
increase engine speed slowly, fan speed must drop, which is heard clearly at a maximal speed of 3500 rpm
Also make sure you are using a 87 degree thermostat.
This might be something to check out:
From the 100.985 engine manual:
18-120 checking the thermostat in the oil filter
insert temp probe in oil supply tank
let engine run and observe temp
at 80-85 deg C a definite increase in temperature must be felt by hand in the oil cooler
note: due to the temp drop between the oil filter and oil supply tank, the temp of the oil in the oil supply tank will be below the opening temp of 95+-4C. fully open at 110 +-4C
OK.good work.! You must be sick of this. :'(
If you have a blockage in the system it will be a partial one... or if the water pump is not delivering the fluid still flows but the longer we run it the less fluid is presenting to the radiator so it slowly gets warmer and warmer. Sure the radiator feels warm and even and we are getting temp differential but gee it getting hot if you run it long enuff.
As I see it, the system from the outlet of the water pump thru the radiator and into the water pump inlet is working fine.
I suspect that the flow in tho from the water pump is not equal to the flow out.
So that leads us to testing the water pump as per my suggestion at the foot of my last email.
The history of that new pump is unknown. So for instance the running clearance of the impellor to the casing could me miles out.
The output should be considerable.
Let's know how you.
The oilcooler thermostat is working fine , when the engine is hot the oilcooler also gets hot it then has ~ the same temp like the oil sump.
I had the waterpump 3 times out , first i just put the used in , i had the impeller of to change the seal and set the clearance according the manual , then i had the the pump out again because the bearing was bad and changed it out with the one from the corroded pump and set the clearance again but a little bit tighter.
The temp sympthom was always exactly the same even with the corroded impeller.
The radiator is not just warm the whole top tank has engine temp when the engine is hot and the whole bottom tank has ~ 15C less.
Well I reckon you've established that everything from the thermostat, hose, radiator, bottom hose is all OK.
That means the "cooling system" tests ok but the "circulation system" remains an unknown quantity.
We know the heater circuit works coz the heater is comfy cozy and we can feel that the return hose is hot. Yes?
Basically the fluid is arriving at the the radiator header tank too hot. Time to test the output of the fabled water pump me thinks.
I see no reason for bad circulation , drove today when we had 36C and with that weather also driving normal the Temp stays at 98 , what i am wondering is that the oil temp was also around 98 everywhere i measured, i always though oil runs hotter than the coolant.
Also the Radiator has 94 C at the bottom tank opposite the outlet , and 90 at the outlet with such outside temps , so even less than 15C difference , if the water pump would not circulate the bottom should be much colder then the top logical thinking.
I also had to the top hose off while the engine was running some time ago when i was flushing the coolant system and the pump was clearly pumping.
Edit:
What i still don't understand is why is this Car behaving exactly like mine :
In the same conditions my temps is the same like in the video thats why i was thinking that a 6.9 runs so hot.
I think it even states in manual that higher temps must be considered "normal" depending on driving and ambient conditions of course.
For example if you are doing a hill climb on 30C+ day for sure the needle will go close to red, but then should come down once you return to more normal conditions.
I always say focusing on what the needle is DOING rather than the absolute gauge reading is the key.
Does it come down or not? Of course if it's pegged in the red and stays there you are in deep shit.
Quote from: ramiro on 26 July 2022, 01:40 PMThe Fan turns off over ~3000 RPM so at 180 it should not make any difference and under 3000 i can clearly hear it.
Can you elaborate on "turns off"? is should definitely slow down though.
Are you using a 87 degree thermostat?
QuoteDoes it come down or not? Of course if it's pegged in the red and stays there you are in deep shit.
After it went a little above 100 it just came down to a hair below the 100 mark at slow driving
QuoteCan you elaborate on "turns off"? is should definitely slow down though.
Offcourse its not turning off completly but you can hear that the fan spins slower
Yes i am using a 87 thermostat tried a 80 and it made no difference at all.
Thats the most frustrating thing so far eveverything i change makes no difference at all (2 Waterpumps , 2 Radiator recores , timing chaing wrong by 1 teeth , different thermostats , flushed the coolant system several times)
There is still the transmission that's also using the radiator, it's shifting perfect, i read that a bad converter can also cause overheating somewhere but as far as i know i don't have any signs for that.
So we have exhausted the obvious and the not so obvious over a period of time/tests and tribulations.
From all of this it would be fair to say it indicates it is running about 10..to 15 deg C above the norm.
That includes unusually hot weather...and some hard punting as well as idle..dawdling around town. etc
So across the operating range of the vehicle, it doesn't matter..it's always indicating hot.
As you say it is exhibiting the same characteristics at hi speed as the 6.9 in the video......I note he hardly had the aircon on?
I doubt you have tranny problems.
The car pulls well and generally seems to have plenty of top end.........I would be staggered if a worn tranny transmitted enuff heat to the cooler to influence the engine temp. It would have to flare and slip like crazy and that is not happening.......
My thoughts turn to excessive backpressure. Worth eliminating........but this would reflect in sluggish performance. particularly a willingness to rev out.........is she all good in that respect?
Now final test. Remove the radiator cap from the reservoir...ensure there is enuff coolant in it to just cover the drain feed to the radiator header.
Start the engine and either drive it until it gets to normal operating temp OR let it idle but either way we want it to get to 87 indicated and then see what happens when it rises beyond. So as it gets warmer it should creep up to a 100....the fluid will expand but not fill the reservoir until it finally boils.....if indeed it does. If and when it boils, what is the indicated temp on your gauge?
Leave the aircon off and pick a day when the temp is perhaps hi 20's.
What is this going to prove?
Well so far, from what I've read [yes I' might have missed it] there are very few symptoms that the engine is actually getting hot...
Yes I know you've had the IR gun all over it but they are largely unreferenced readings.
You have reported pinging at 180kph: but not that it is boiling and puking fluid everywhere.? An engine getting this seemingly hot should not be holding its coolant.
There's another odd thing........does the engine get "heat soakback" when turned off?. ie boils after it stops and vomits fluid everywhere.?
Would you humour me and explore this avenue? ::)
No when i drive fast there is no Limit to the temp it will go to the red mark i just slowed down when it had 115 , but the car in the video also would go further in temp i think at least is was going up till the end.
QuoteMy thoughts turn to excessive backpressure. Worth eliminating........but this would reflect in sluggish performance. particularly a willingness to rev out.........is she all good in that respect?
Well it got to the rev limiter in last gear at 250 according to speedo so i think engine perfomance is fine, allthough in 2. gear it feel slugish above 4500 but i thinks its normal.
I am pretty sure the temp is real , i can see it staying some time at 87 when i drive slow as it should.
When i turn the engine off the temp creeps up but i never turned it off when it was above 100(because it usually cools down to around 100 when i go off the highway and drive slower) so it had no reason to boil out.
Yesterday after it went above 100 the Radiator hoses were very hard and even after 2 hours they still had pressure left, when the engine stayed below 100 i was able to take the cap off without anything comming out just a tiny little bit of pressure.
Something screwy here. The engine should build 12 lbs of pressure or more........when you pull into your driveway after a thrash and the temp has dropped from 115 or whatever to a 100; and you pop the radiator cap, it should erupt volumes.
All you're getting is a bit of pizzle.??......no boiling water .no massive release of pressure... and no pressurised water???
It has all the characteristics of not really being hot... yet? ::)
What happens when you drive it with the radaitor cap simply not on?
Hello again ,
I did change the headgaskets now because i had enough , the rear part off the block was full with rust and the valve guides and seals were completly done and 1 exhaust valve also had a crack.
The car finaly has a perfect idle and there is no more blue smoke from the exhaust.
But my temperature problem is still fully there slowly i am out of ideas what still could be tested i did the the testdrive with a afr meter hooked up it was a little rich so that couldn't be the problem , it behaves exactly like before, and yes it is really getting hot everything thats has to do with cooling is over 100C when the gauge shows over 100C also the AC fan is running.
MfG
Ramiro
The first 3 pictures are fascinating, but I cannot tell where in the engine you took them. Is it possible the entire block passages are full of rust and thus have poor ability to transfer heat? The picture of the piston head looks odd. Is that rust deposits on it?
OMG!!!..........what a job. That block must be full of crud. Try running the water pump with the top hose diconnected and see if it's shifting the fluid for astat.
The first 3 picture are the top cooling passages from the 4. cylinder that was the worst place , the front cooling passages were clean.
If I understand correctly the first photos are looking down super close into the water jacket. If so - to me it is incredible that there could be this amount of layers of corrosion within an engine. Makes one look again at the options for cleaning out a cooling system on a regular basis.
I dont know if hot tanking the block would even get all that rust out. You would need to consult with a machine shop and see what they think.
This may be and idea:
https://www.evapo-rust.com/restore-your-engines-cooling-system/
You might need to soak it for a 3-7 days a few times and see how much rust it removes.
I had a german alternative to evapo rust already for serveral days in the engine after i manual cleaned the block(actually 2 times , first before i put the heads on and the after that i filled the whole engine again for serveral days) , the phots were from the worst spot and it was mostly loose rust , but all the small passages between the cylinder were blocked.
But i don't believe that it has to do with rust in block because the temperature didn't change at all after i put the heads back on , and it's definitly much much cleaner then before.