Still overheating (grrrrr!)

[michaeld]

Requesting a little diagnostic assistance on an overheating 77 450sel.

I'm getting hot at all temp ranges.  It takes 1/2 hr - hr to get to appx 212F on the freeway; gets that hot w/in about 10-15 min at idle.

I replaced the thermostat (and checked the old one; it was opening at the 167F/75C mark).

My non-contact thermometer tells me that the radiator is not blocked; it showed pretty consistent readings from 5 different "shooting" points w/ the car at idle after a short drive.  There was about a 20 degree (F) difference in temp between the upper and lower hoses.

I called a helpful MBz mechanic from Laguna Nigel MBz; he thought it was most likely the fan clutch.  I placed a balled-up rag in constant conctact w/ the fan as he suggested, but it easily spun through that resistance.  If anything, the fan clutch is not DIS-engaging, as I was never able to feel it spin freely/disengage even when the temp was under 167F/75C.  I also tried to use compressed air from my blower, but the fan easily turned through that resistance also.  There is no oil fouling on the fan clutch that I can see.

Does that pretty much mean I MUST have a bad water pump by default?  The pump is not leaking or making any noises.  Also, it is only 3 years and 4000 miles old (w/ 3000 of those miles put on by me in the last 7 mos).  The MBz Tech Companion suggested feeling the hoses for "pulsation" from the pump; I did NOT feel any.  I'm also not sure whether I'm getting any coolant flow, but it is so hard to see from the overflow tank (particularly if I'm not getting any).  Any insights on testing the water pump and coolant flow would be much appreciated.  If the pump is bad, why did it fail so darn quickly?  The PO was a medical doctor (= rich dude) who did NOT use crap parts or Pep Boys-type mechanics.

The shop rate shows 4 1/2 hours for a water pump (which probably means 2 days and a good 2 pints of blood for me!).  It's not a pretty job on this car from the looks of it.  I'd sure like to have a better "feeling" about what is wrong before I start replacing expensive and labor-intensive parts willy-nilly.  And I'm darned sure I don't want to pay 4 1/2 hours at $80/hr!!!

[Nutz]

Hi Michaeld,

It's not common but sometimes the impeller on the water pump can fail resulting in it not circulating coolant.Remove the belts from the water pump pulley and spin the fan by hand.What you want is for it to spin but not as if there is no resistance whatsoever.

If it were me I would test the engine with a vacuum gauge to rule out the possibility of a leaking head gasket before going any further.If the needle on the vacuum gauge fluctuates from 10 to 23 in./Hg. as the engine rpm's are increased then this will confirm it.

[s class]

Another check for the water pump - remove the belts, and disconnect the upper radiator hose.  Leave the lower one connected.  I you then spin the pump in the normal direction you should see it squirt out a bit of water where you removed the hose.  Be aware that you may have to spin the pump quite vigorously to get the squirting.  If you absolutely cannot get it to move any water, probably the impeller is worn or disconnected.

Ryan

[kenny]

Are you absolutely certain your ACC servo doesn't have some sort of leak?  How about all the heater hoses where they go through the firewall?
Your pump could be bad even though it seems too young to die.
I had 2 pumps in 3 years on my 6.9.  It can happen.
Don't assume the newness of your parts excludes them from the list of suspects.
Take all the advice you've received and systematically go through the cooling.

I know you don't want to hear water pump, but don't rule it out.

[alabbasi]

Could it be that your just dealing with the hot weather? My 6.9 gets hot really quickly at idle this time of year. I'm thinking of installing a big electric aux fan to help this.

[michaeld]

Thanks for the responses, guys.

At this point I think I'd actually be dancing if I were to find out I needed to replace my water pump; at least I'd know what needed replacing!  The water pump appears to be a tough job, but one I believe is within my limits.  And I'd darned sure prefer a bad water pump to a bad head gasket (If I had the latter, I'd probably have to walk away from the car ).

Let me put my questions right here, so everyone can see them w/o reading the rest of my post:
1) Where does one connect a vacuum gauge on the intake manifold?  I don't know vacuum sources, having never messed w/ them before.
2) How does one assess whether the coolant system is circulating on our (radiator cap-less) systems?
3) Could anyone feel their upper and lower hoses and report what they feel (i.e. water pressure, pulsation from the pump)?

There's a list of what I've noticed at the very bottom of the post.

Now, when Kenny raised the dire possibility of a head gasket, he suggested a vacuum test.  I've never done one (tho I DO have a Mityvac I bought for brake work).  I read that one should install the vacuum gauge to the intake manifold beyond the throttle plate; I know what and where an intake manifold is, and I know what a throttle plate is - but I still don't know where to actually connect my gauge.  Could anyone provide a specific part/source for vacuum, and give me an idea where to find it on the intake manifold?  I tried reading up on vaccum tests online, but didn't come away w/ meaninful info on "where in the heck do you connect the darn thing." 

On the topic of head gaskets, thus far my car has NO visible symptoms of a cracked head gasket.  There is no white smoke, no oil/coolant where there shouldn't be, no gunk in the oil cap, or any noticable loss of power.  It is also hard for me to believe that I could have this kind of overheating due to a head gasket that is showing no other signs of problems.  I would like to go ahead and do both a vacuum and compression test (just to assess the condition of my engine), but don't know how to do the former.  I have heard that there is a compression leak test (aka block test) that is fairly simple and straightforward that would tell me if compression gasses were leaking into my cooling system.

Something is wrong w/ a cooling system that goes through water pumps the way Kenny's (and mine?) have.  I've never had a problem (or heard of one) like that before.  I'd sure like to know what's going on.  Could it be sludge buildup that fouled the first pump, and then wasn't removed?  Should fork over the bucks to have a reverse power flush done?  I'd flush my own system, but if my pump isn't moving water, it won't do much good.  How does one assess whether the system is circulating when one doesn't have a radiator cap?  I can say that there is a 20F degree diff between the upper and lower hoses.  Does this mean my pump is circulating?  If so, then what else could be causing my overheat condition.

Alabbasi,
The night I first overheated was cool (for S. Cal) and the drive was more downhill than uphill.  By the time I got off the freeway and shut her down, I was just shy of reaching redline.  I've definitely got a problem.

My next move will probably be to replace the overflow cap, the upper hose (lower already done when I did the thermostat), and the belts.  I'll also do a pressure test (which I haven't done).  The latter don't look bad, and seem to have good tension, but I guess I need to eliminate them as a possibility.  When I get to that point, I'll be in position to check the water pump per your methods.

I would simply replace both the water pump and fan clutch, but at this point, I STILL don't know if that would solve my problem.

Here is ALL the data I've gleaned so far:
1) When I overheated to point of being close to redline, my coolant level was ALL the way to the top of the overflow cap.  The system did not boil over, or steam.  But there was a LOT of pressure there.  I looked around w/ my flashlight, and saw no signs of leaks anywhere.  I also do not smell coolant in the car.  The coolant level remained fine throughout the drive.

2) Since draining the system to replace the thermostat/lower hose, I've frequently had to add coolant.  It is possible that I NOW have a leak (that I didn't have that first night), but I am suspicious that if I'm not circulating, the coolant may not be getting to all the places it's supposed to be, and thus I need to add several times to completely fill the system.  My coolant level remained fine the night I experienced the overheat, and stayed fine for half a dozen or more drives thereafter until I drained the system.  Following that, I've had to add coolant several times after short test drives to get the right level.

3) I am getting hotter than I should at both idle and on the road.  Since that first night, I've been pulling off if before getting to 212F to protect the car.

4) I feel heat from both my hoses with the car idling and warm.  But I don't feel pressure, or pulsation (from the pump).  Can anyone tell me what they feel when they grab their radiator hoses?

5) I 'shot' the radiator and the hoses w/ my non-contact thermometer while the car was idling hot.  There was very little difference at several points on the radiator (which I interpret to mean it's not blocked); and there is a 20F degree difference between the upper and lower hoses.

6) The (drained) coolant has looked good and lime green; it is about 6 mos old.  I have re-used the coolant, figuring I'd replace it when I fixed what was ailing the system.  When I've drained, there has been a TINY bit of residue on the bottom of the container containing the coolant, but nothing out of the ordinary (i.e. it doesn't appear to be from massive sludge build-up, or from oil getting into the coolant).

7) I tried the method suggested by a Mercedes mechanic to test the fan clutch.  I let the car get to operating temp at idle, then used a rag to stick into the tip of the fan path so that there was contact.  The fan spun easily through the contact.  I also tried compressed air, w/ the same result.  There is no sign of oil seepage from either the fan clutch OR coolant seepage from the water pump.  Neither are making any noise.

I checked my timing, and am w/in 2 degrees (at most) of spec (TDC).  I could not imagine that that little difference between spec and observed could cause me to overheat, and did not set the timing.

I sure would like to isolate my problem.
Thanks for your replies, and your advice.  Many of you are more knowledgable than I am at "car fixin'." 
Mike   

[s class]

Michael,

If' its any consolation, based on your report I would agree that a head gasket problem seems unlikely.  I assume you've checked that when the temp gauge shows overheating, the car really is hot - in otherwords its the truth.  I assume this is the case as you talk about the overflow tank filling up. 

I have had block tests done on cars in the past and my experience is that its not a black/white test.  On older cars with older coolant, even if there is no head gasket problem, I've seen the fluid in the tester change colour slowly.  If that happens to you, don't dispair yet.  If you really had a head gasket leak, the fluid in their tester would change colour very quickly. 

The only thing I can think of is that you have a blockage somewhere in one of the coolant passages in the block or head.  It is just possible that when the water pump was changed, some foreign matter was allowed into the water system and it sat there harmlessley until it became dislodged for some reason and moved to where it now is causing a lot of problems. 

What say you guys - a blockage or partial blockage somewhere?

Depending where it is it could be very difficult to verify or remedy. 

Please don't walk away from the W116 - persist and you will solve this. 

Ryan

[kenny]

I know we don't want to recreate the wheel here so I won't get up on my soapbox and start preaching about green coolant, but in the most diplomatic possible terms, I would suggest that you go to the MB coolant when you get this sorted out, and I believe you will get it sorted out.  If you search around, you'll find at least 20 years of debate on the subject.
I wouldn't suggest that this is all or part of your present problem, just an idea for going forward.

I, too bought my car from a rich guy, named Albert Alkek, who used to be Harry Sinclair's bag man, but that's for a different discussion.

I made assumptions about his wealth and ability to care for the car I was buying.  Nevertheless, I found that he had used some sort of stop leak product in the cooling system.  My first failed servo revealed all the chalky hardened stuff when I took that sucker apart to see what made it tick. 

There's a procedure outlined in the manual for a citric acid flush which can dissolve lots of what may be blocking the system.  It's probably a good maintenance item for a desert dweller who must have a properly operating cooling system.  I can't remember exactly, but wasn't your radiator blocked?  Any crud in the radiator would have certainly circulated throughout all the cooling passages.

Have you noticed any moisture on the passenger side carpet?  Any odor of coolant inside the car? (edit) I see there is no coolant odor.

I am not a mechanic by any means, all I have going for me is some experience with similar, not identical problems and I am not smart enough to diagnose by what's been reported.

I hate to sound like a broken record, but any time you replace a hose or thermostat or have a boilover, you must be sure that you get a proper refill and burp all the air pockets out.  You indicate you have had to add coolant a few times after short drives to get the level right.  That suggests an air pocket that wasn't completely displaced, even though you must have thought it looked full. 

You may have entirely solved the problem with a new thermostat, only to introduce a new one that looks identical by an improper re-fill.

On the brighter side, you are gonna have a really great cooling system when you get this solved, you'll have checked out every possibility for failure.

Did I ever tell you the one where I overheated in the Texas Canyon outside of Willcox Arizona when it was 115 F., and everybody must have assumed I had a cell phone because nobody stopped?  Either that or they thought that an MB owner deserved a nice suntan.  One guy did stop.  He said he couldn't help, but he saw my Texas license plate and pulled over to tell me he had lived in Dallas once.  I felt relieved immediately.  15 miles to Willcox took about 3 hours of cooling completely and driving until the temp needle started getting too high and pulling over again. remind me to tell you about that one.

I mention this because I know you want to avoid something like that.

Keep posting results of your tests and it will get solved.

[Denis]

Hi fellows

I believe that kenne y and S  class has some good insight here. Scientific thinking says that the simplest theories that explain what is observed are often the best. Sure the head gaskets may be shot but what about plain poor cooling system performance ?

FWIW, over the years, I have seen a lot of people change parts due to overheating engines when they really needed a major flush/backflush.  The heat is produced in the cylinder heads and around the cylinders and sure enough the whole system needs to remove the heat from the coolant. But what if the coolant cannot contact enough metal surface to remove the heat it is storing ?

I have seen incredible crap come out of the bottom of iron cylinder blocks. When was your system CLEANED out, not just drained ? Jokingly, you might think that sand from the casting process had been forgotten in the block when you see the sediment come out. Remove the screws at the bottom of the block and try flushing/poking from there. If you find sediment, do a complete backflush...in fact do it two or even three times 

This might help...

Good luck

Denis

Paris, France

[michaeld]

Thanks (again) for your responses, guys; when your car is sick and you don't know what to do you just feel so.... lost, confused, and forlorn.  Sometimes when your in this boat it just helps to have some mates say, "I feel your pain."  I appreciate the pep-talk-pick-me-ups.

I WOULD LIKE to do a pressure backflush of my system, but so far I haven't found anyone who is doing these.  I don't really even want to bother w/ a normal hose-flush at this point, as I am not certain that my system is circulating (also, w/ this system, I'm frankly not sure how to do a "hose job" as every other system I've ever worked on has had a radiator cap -- Gosh, I sure miss those radiator caps!!!).

As I said, if I knew where to connect my vacuum gauge, I'd do the test.  If anyone knows, please post!

Some good news; the folks who replaced my radiator core told me they'd inspect my system free of charge.  I'm just kind of lost as to what to do at this point, and I probably need the diagnostic skills of a mechanic.  And those guys struck me as actual mechanics.  I will bring the car in to them Monday, and hopefully they'll help me sort things out [and come to think of it, they might be able to do a backflush; I forgot to ask them].

As for Kenny's comment about improper burping being a possibility; I can't deny that I'm confused about proper burping protocols.  Again, this is the first time I've ever owned a car where this was an issue.  So far, I've been trying to pour the coolant in very slowly and evenly, and trying to have the front end facing uphill when I've done it.  That's all.  As a new Benz "parent", I would appreciate a "burping lesson so I can properly tend to my baby.

And as far as Kenny's comment about green coolant, I'm telling my car, "Hey, I'll run anything you want, old girl; just stay cool!"  I don't run synthetic oil because I do frequent oil changes; but coolant (which stays in the car for two years if all goes right) is another matter.  I've also heard distilled water is much better than tap.

And lastly, to Kenny's comment about crazy rich guys, I'd say that if my car has stop leak, it's because some mechanic put it in.  I've got about $25,000 worth of service records to back up my belief that he just didn't sully his hands w/ car-stuff.  He tended to take the car to the same mechanics for serious periods of time.  You never know, though.  I certainly wouldn't put that crap in any car I was planning to keep.

I have been smelling about my interior like a person who's trying to figure out if someone in the room farted ( ), but thus far I don't smell anything different.  Nor do I feel any moisture.   If my servo has gone bad, I would do a $500 digital bypass that I've heard about, as it's just something that one can expect to go bad in these cars; if I have to spend $2000 to have a $40 head gasket installed, that's just another matter entirely.  If I could figure out how to do that vacuum test, I would feel a LOT more comfortable about investing money into this car.
Mike

[Nutz]

Here you go michaeld,

Connecting the vacuum gauge, I hope the pics I took are clear enough. Off to the driver side (US) of the airflow sensor towards the front is a constant vacuum source.Let me know if this helps 

[michaeld]

Nutz,
THAT'S what I needed.  Someone once said to me, "What, are you a dumbass?  Do I need to paint you a picture?"  And I said, "YES!"  Thank you, Nutz!  I'll have to invite a friend over to play with the accelerator pedal whilest I watch the gauge.  But you've given me what I needed.  If all is generally okay w/ my engine, I'll be a lot more content taking care of the car.

Styria,
I replaced the thermostat w/ a Behr, and replaced the lower hose (the upper and a couple of belts I figured I'd order when I bought whatever cooling part I needed).

I won't be sure what brand of water pump is on the car now, but I will be surprised if it isn't a German-made OEM.  As for me, I am finding a Graf and an Airtex model for about the same price ($82 US); a new Behr fan clutch will run me $133 US (I've bought several parts from mercedes-benz-parts-direct.com, and been quite satisfied w/ their low prices and 2 day delivery).  I have called dismantlers all over S. California, and have yet to find a wrecked 116!  When installation is a PITA, new is better in my book.

I'm certainly going to do some kind of professional flush.  The folks that replaced my radiator core 8 mos back charge $90 for a backflush.  If they recommend getting even more medieval on their flushing procedure - and it's in the range you're describing - I'll probably go for it.  If my water pump is bad, it's possible that undealt-with-gunk killed it.  I know I won't be able to deal with it w/ a garden hose and radiator cleaner. 

Assuming my pump needs replacing, I would probably tend to start taking things apart and assess how much of a pain it would be to replace the fan clutch later on.  If it looks like it would be a royal pain, I'd probably order the fan clutch.  But in general I don't really want to replace parts that aren't bad yet, as I am more-or-less saving money for that coming day when my servo dies.  If only I had a money tree in my backyard!  [The fan clutch was replaced in 1990 nearly 45,000 miles ago; it certainly wouldn't be stupid to replace it with the pump given the fact that they units often fail about the same time].

In any event, this forum is fun when things are going good w/ my car; and essential when they aint! 
Mike

[Nutz]

No trouble at all michaeld,I hope you get it sorted out  If your buddy can't make it over to press on your gas pedal .....

[michaeld]

Nutz,
That is also good to know.  Having the friend on the accelerator is nice because I wouldn't have to hook up my analyzer and pay attention to rpms AND the vac gauge.  But I'm glad you pointed out the location, as I have never had the airbox off the manifold before and would have been searching around for the throttle linkage.

I would like to get some spark plugs and do the compression test (and then the vac test) at that time, as I figure if I'm gonna take them out, I may as well replace them.  Only Napa stocks the plugs locally, and they are a bit of a drive away.

I'm sure that anyone in the future who wants to do a vacuum check on a w116 will be as grateful to you as I am for including these pics.
Mike

[michaeld]

Update:
I drove to Autozone to pick up a pressure tester and suffered a minor disaster after getting home; the upper hose (which I damaged while replacing the hose clamp and had to tape up until ordering a new one) popped off the water pump, spraying hot coolant everywhere.  What a mess!  But... Thank God it waited until I got home!!!

I tried to "burp" properly this time: I parked on an incline, front end up.  Poured coolant in until I could just see it appear in the overflow.  Started the car.  Waited until the thermostat opened and I could see the coolant in the tank disappear.  Topped off.  I forgot to turn the heater on full blast, but I did have it on auto low set to max heat.  If there's more to the magic of burping than this, please tell me.

I pressure tested the system after the car cooled down.  I should have done this at the beginning, but frankly thought I was holding pressure.  I have a 14lb pressure cap, and I pumped the pressure to 14 lbs; after 5 minutes, it was still holding 14 lbs.  In fact, I let the system sit for 5 min, then realized that I didn't have it fully at 14 lbs, pumped it to that level, and let it sit for 5 more minuetes.  If the needle budged at all, it was so imperceptible that it was w/in my eye's parallax error potential.  So she's holding pressure.

Here's the first question: does that (i.e. holding pressure) pretty much completely rule out a bad head gasket, OR a problem w/ my (unseen and virtually impossible to access) heater core?

I then used the pressure tester to try to test the cap (never done that before).  According to my Chilton manual troubleshooting guide, if the cap released w/in +/- 1 of its 14 lb rating, it is operating properly.  I pumped it up to 16 lbs, and it never "released" (whatever the heck that means.  I don't know what a "release" looks like, but it didn't do anything at all). 

Thus my second question: could a bad pressure cap be the cause of all my maladies?

I've been a cheap sonofagun, trying to wait until I had another minimum $50 dollar order before ordering a new hose and cap.  I would have ordered by now and eaten the shipping, but the place from which I've been ordering only has an expansion tank cap marked at 120; mine's 140 (14 lb).  I think I will want to replace the upper hose and cap before taking the car down to the mechanic for the backflush, as I am terrified of the upper hose popping off or rupturing again.  If it popped off, not only would I lose coolant in a hurry, but the hose would become entantled in my fan blade and cause Lord-knows what kind of disaster.
Mike