Author Topic: 350SE - do I need to take these heads off?  (Read 6219 times)

s class

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350SE - do I need to take these heads off?
« on: 05 February 2011, 10:06 AM »
Im working on a nice 350SE that has run for a long time with no anti-freeze.  Today I removed the inlet manifold for the following reasons :

a) the steel heater pipe under the inlet manifold was badly corroded
b) lots of vacuum leaks -

The heads have previously been removed on this car, and the reassmbly work was pretty poor.  Some of the inlet manifold bolts were finger-tight, the rubber boots not properly seated etc etc. 

Anyway, with the manifold off, I found this :



See those brown streaks running down the vee..... do we have head gasket leaks here or not?

left bank :



And a close-up, with the camera placed in the bottom of the vee, looking up at the underside of the left head :



right bank :



And a close-up, with the camera placed in the bottom of the vee, looking up at the underside of the right head :



Opinions please guys - those are streaks from rusty dirty coolant, but I wondered if its old marks, or who knows?  Ominously, they are located at the position of the water channels in the head gaskets....

Its probably wishful thinking to presume I could just try retorquing the head bolts?

BTW today I had only two sheared off manifold bolts - the front most one on each of the two sides.  I've progressed well with drilling them out, I will finish that job tomorrow. 

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL

koan

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Re: 350SE - do I need to take these heads off?
« Reply #1 on: 05 February 2011, 02:02 PM »
Its probably wishful thinking to presume I could just try retorquing the head bolts?

I think if I was presented with that situation I would have to pull the heads and fix it properly, really depends on what the owner is willing pay.

Might get away with retorquing the bolts and maybe a can or two magic leak fixer, who knows.

koan

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WGB

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Re: 350SE - do I need to take these heads off?
« Reply #2 on: 05 February 2011, 03:37 PM »
I would assume if the owner didn't pay for coolant he may baulk at a full head off rebuild.

I would be more interested in history - coolant consumption, any combustion products in the water - as well as a cpmpression test which is probably not possible now.

I would agree with Koan that it is probably reasonable to fix the leaks you can see, refit the inlet manifold and then re-torque the heads and see what happens but with the the strict understanding from the owner that more work may be required after the motor is reassembled if there are

1) further coolant loss problems
2) Cooling system pressurisation test fails after re-assembly.
3) Problems with compression test
4) All of the above.

Bill

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Re: 350SE - do I need to take these heads off?
« Reply #3 on: 05 February 2011, 10:17 PM »
Thanks guys.  The present owner recently bought the car from a collector.  He has only done about 500km since buying the car, and we can't make any comments on coolant consumption because there were so many other leaks (split hoses, cracked header tank etc). 

THe present owner is not the one responsible for running without antifreeze. 

I did do a compression test before I started disassembly.  The results were rather ordinary (for an engine with 130 000km), but I dismissed the poor results as being at least in part to sticking rings, because the engine was running VERY rich due to WUR problems.  The spark plugs were absolutely clogged with soot. 

cylinder        dry test (kPa)      wet test (kPa)
1                  750                       850
2                  780                       800
3                  600                       800
4                  900                       900
5                  700                       900
6                  750                       900
7                  750                       850
8                  740                       780
variance       300                       120

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL

TJ 450

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Re: 350SE - do I need to take these heads off?
« Reply #4 on: 06 February 2011, 07:51 AM »
I tend to concur with Bill, seeing as it's someone else's car.

The first thing I would check is the torque of the head bolts in the area(s) of the stains. It could also have been leaking from the manifold and somehow tracking along the gasket edge (probably unlikely).

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

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Re: 350SE - do I need to take these heads off?
« Reply #5 on: 06 February 2011, 09:22 AM »
TJ, there is leakage from the water channels at the front of the inlet manifold, but those streaks down the valley very definately come from the head gaskets. 

But I agree with you that I should check the head bolts.  Its the only simple thing I can do at the moment.  It may not cure the problem, but if I find loose bolts, it will at least help to confirm the diagnosis. 

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL

s class

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Re: 350SE - do I need to take these heads off?
« Reply #6 on: 08 February 2011, 10:35 AM »
Progress update - I've had a discussion with the owner of the car, and we have decided that I will pull the heads, and see what we find, with the intention of fixing it properly. 

Given the low mileage of the car, I would like to think that the bores will be good, but one never knows.  I will soak the rings in ATF while the heads are off in the hope that we can loosen them up a bit. 

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL

WGB

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Re: 350SE - do I need to take these heads off?
« Reply #7 on: 08 February 2011, 03:07 PM »
Sounds like he really wants to keep the car and look after it which is great.

I hope water hasn't got to that No 3 cylinder.

Bill
« Last Edit: 08 February 2011, 05:10 PM by WGB »

s class

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Re: 350SE - do I need to take these heads off?
« Reply #8 on: 09 February 2011, 12:30 AM »
Agreed, the compression results on #3 are very poor. 

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL

TJ 450

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Re: 350SE - do I need to take these heads off?
« Reply #9 on: 09 February 2011, 03:08 AM »
I'm thinking along the lines of Bill. If there was water leaking into #3, it could be a situation not unlike my 190E. That engine only has 120,000km on it, however as a result of the blown gasket it now has second oversize pistons in it.

Fingers crossed this isn't the case here.

Tim
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1969 300SEL 6.3 1394
2003 ML500

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Re: 350SE - do I need to take these heads off?
« Reply #10 on: 20 February 2011, 01:44 PM »
Today I removed the heads, and I'm afraid it was a tale of the good, the bad and the ugly. 





The good : I had NO broken exhaust studs or head bolts. 
The good : the heads have been replaced at some point and they are actually pretty good.

The bad : the heads a date coded 1976, and this car is a 1980, so this is confirmation of the head replacement.  I believe I found the reason for the head change - this engine has jumped its chain in the past.  There is evidence of the chain having run against the dowels of the guides, and a few other places. 

The really bad : the person who fitted the 1976 heads retained the 1980 cams and cam towers.  THis is evident because there was a change in diameter of the cam oiler line.  The small bore 1976 oilers had been fitter onto the 1980 towers intended for the large bore oiler.  The plastic oiler fittings seem not to have been changed, and were fitting loosely onto the cam towers.  I just picked up the oiler off the towers without any pulling force.   :o



The really, really bad : with all the rockers removed, the cams were impossible to turn by bare hand.  It required a spanner on the sprocket retaining bolt, and considerable force on the spanner to turn the cam.  Obviously the tower bores are misaligned due to swapping heads but not pedistals. 

The ugly : with the heads off I found this :

All cylinders : a very obvious lip at the top, easily felt with a fingertip (even after cleaning the carbon off).  There is no evidence of hone marks anywhere.  the cylinder surfaces are completely glazed. 

Cylinder 4 :

This area of scoring is easily felt with a fingetip.  It feels like coarse sandpaper actually. 


Cylinder 3 :




The carbon deposits extend well below the ring lands at the rear of the bore.  So the first one or 2 rings are either very stuck or they have lost their temper. 

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL

WGB

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Re: 350SE - do I need to take these heads off?
« Reply #11 on: 20 February 2011, 03:18 PM »
Itsounds like you are not finished yet.

Are there many second hand 350 motors about or is it possible to upgrade to a 450 motor?

A full re-build of that one will still mean looking at the heads plus ?that motor almost appears to have seized at some stage.

Bill

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Re: 350SE - do I need to take these heads off?
« Reply #12 on: 20 February 2011, 04:14 PM »
That is disappointing, it sounds like the motor has been cooked.

Tim
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1969 300SEL 6.3 1394
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Re: 350SE - do I need to take these heads off?
« Reply #13 on: 20 February 2011, 08:30 PM »
Certainly this is disappointing. Are you saying that those score lines are from heat seizure?

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL

WGB

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Re: 350SE - do I need to take these heads off?
« Reply #14 on: 20 February 2011, 10:30 PM »
Certainly this is disappointing. Are you saying that those score lines are from heat seizure?

That's what it looks like to me - either complete or momentarily and then put back into action as cheaply as possible without even the correct coolant.

It will need a lot of work to get that motor to work as well as it might.

Bill