Head gasket & advice on top end rebuild?

[DRW]

Hi and thank you in advance for any attention. There are many threads on head gasket replacement. Of course, I might as well include a valve job etc. I'm looking for a comprehensive list of items to be replaced, since I'm faced with this big job. I use my 500E as a daily driver and I'll look to use it as my casket someday. 81K miles and the head gasket is blown, probably due to a big overheating a few months back. Yikes! Thinking of an engine out job, to get to as many bugs as possible..

Thank you for any advice.
David
'92 500E

 

[gsxr]

David, what are the symptoms indicating a blown head gasket? And how bad was the overheating - did the temp go into the red zone (over 120C)?

Anyway, even at only 81kmi, there's a huge list of "while you're in there" stuff. Particularly all the chain rails, and pulling the front cover while the heads are off. Highly recommend pulling the engine if you have the time & space to do so; and also pulling the trans for an external re-seal, replacing the trans tunnel insulation, P/S low pressure hose hiding behind the heat shield along the frame rail, and a lot of other stuff. There was a thread a few years back (possibly a couple threads) that went into more detail on what to do while the engine was out & apart.

 

[DRW]

Wasn't the head gasket after all. Got lucky.

 

[gsxr]

So, what was the root cause...?

 

[gerryvz]

Wasn't the head gasket after all. Got lucky.

It would have been REALLY unusual for an M119 to blow a head gasket.

 

[Patrick 95]

Hi, where can I look to find the engine number to order parts. I know it is a M119 of 4.2 litres but there were several versions of it. Mine is a 1995. I need intake manifold gaskets, head gaskets etc. I think mine is a "open deck" version. What I am looking for is something like M119 ### ## ## something like that. Thanks all.

 

[Pat]

Looking for info on head gasket replacement for my 1994 E420.

 

[gsxr]

What are the compression numbers for all 8 cylinders, and was the test done hot or cold?

What other symptoms are present? I wouldn't automatically assume it's a failed head gasket... that's a huge, expensive job and almost no M119's ever need head gaskets replaced.

 

[Pat]

It would have been REALLY unusual for an M119 to blow a head gasket.

First two cylinders on the driver side have low compression (100 psi, other six have 180 +/-) on my 1994 E420. Car always ran hot, not overheated but hot, until I replaced the fan clutch, now it never gets to 100 on the temp gauge. I'm wondering if years of too hot operation has deteriorated the head gaskets. No coolant leak or coolant in the crankcase, just a nasty double miss and the low compression. Hard to find good info on where the timing marks etc should be configured before pulling the cams and head.

 

[gsxr]

The FSM has all the info you need on cam timing / marks / etc. Also more info on this forum if you search.

You might want to do a leakdown test before pulling the head.

 

[Pat]

first two cylinders on the drivers side have low compression (100 psi +/-) all others at 180. It's been a while, but I think the engine was cold when I tested. No coolant leak or coolant in the crankcase, just a nasty missfire on those two cylinders. Car had always run hot, not overheated but hot hot. I replaced the fan clutch and now heat gauge never reaches 100. Previously the electric fans have always come on as temp gauge crept up, but temp gauge would go back down as the electric fans run. So I have guessed that continuous hot operation has deteriorated the head gaskets. I'm looking for a starting point, where to set the timing marks to start disassembly etc. Car is a 1994 E420 with around 140,000 miles.

 

[gsxr]

The FSM has all the info you need on cam timing / marks / etc. Also more info on this forum if you search. You'll need to follow the FSM procedure if you do remove the head. This is not a "wing it" kind of job.

You might want to do a leakdown test before pulling the head.

 

[Pat]

Sorry, what is the FSM?

 

[gsxr]

Factory Service Manual:

Mercedes Benz Model 124 - M119 Maintenance Manuals

 

[Pat]

Thanks gsxr. I'm not a wing-it mechanic. A bit slow maybe, but I could fix a broken nuclear reactor with enough time and the internet lol.

 

[gerryvz]

First two cylinders on the driver side have low compression (100 psi, other six have 180 +/-) on my 1994 E420. Car always ran hot, not overheated but hot, until I replaced the fan clutch, now it never gets to 100 on the temp gauge. Im wondering if years of too hot operation has deteriorated the head gaskets. No coolant leak or coolant in the crankcase, just a nasty double miss and the low compression. Hard to find good info on where the timing marks etc should be configured before pulling the cams and head.

It depends on what you mean by "ran hot" -- these engines can run all day at temps up to 110C with zero ill effect. I ran my G-wagen's M104 at 110-115C for a couple of years with zero negative effects, until I determined (after replacing radiator and fan clutch twice) that a faulty thermostat was the culprit. The M119 has very robust head gaskets. I would take the @gsxr's advice and do a leakdown test in addition to the compression tests. If you are not losing coolant (other than normal modest evaporation loss of coolant) then I don't necessarily think you have head gasket issues.

As far as timing marks and such, all of that is detailed in my post here, as well as on @gsxr's web site (www.w124performance.com) in the M119 photos section as appropriate. As said, all of the information is very clearly laid out in the factory service manual, as well.

 

[Pat]

It depends on what you mean by ran hot -- these engines can run all day at temps up to 110C with zero ill effect. I ran my G-wagens M104 at 110-115C for a couple of years with zero negative effects, until I determined (after replacing radiator and fan clutch twice) that a faulty thermostat was the culprit. The M119 has very robust head gaskets. I would take the @gsxrs advice and do a leakdown test in addition to the compression tests. If you are not losing coolant (other than normal modest evaporation loss of coolant) then I dont necessarily think you have head gasket issues.

As far as timing marks and such, all of that is detailed in my post here, as well as on @gsxrs web site (www.w124performance.com) in the M119 photos section as appropriate. As said, all of the information is very clearly laid out in the factory service manual, as well.

I visually inspected the valves, they look good to my eye. It's curious that I never had oil and coolant mix, my only symptom was low compression in one or two cylinders and poor performance and the car would not pass smog testing. My main question is could compression be lost even though the steel ring seen here is all intact? My inclination is to check the head and block for warp then proceed with new gaskets and leave the 32 valves and lifters alone. This gasket is from the right bank, left bank is similar but not as bad. The picture with mostly only one cylinder shown is the #1 cylinder and the one I could hear the hissing of lost compression in the leak down test. I'm also replacing all the plastic/nylon timing chain guides including the ones behind the timing cover.

 

[gsxr]

Test the valves properly (not just eyeballed) before installing the heads. You may still have a leak at the valve seats. Don't want to put it back together and find out it still fails a leakdown test.

 

[JC220]

View attachment 163253View attachment 163254

I visually inspected the valves, they look good to my eye. Its curious that I never had oil and coolant mix, my only symptom was low compression in one or two cylinders and poor performance and the car would not pass smog testing. My main question is could compression be lost even though the steel ring seen here is all intact? My inclination is to check the head and block for warp then proceed with new gaskets and leave the 32 valves and lifters alone. This gasket is from the right bank, left bank is similar but not as bad. The picture with mostly only one cylinder shown is the #1 cylinder and the one I could hear the hissing of lost compression in the leak down test. Im also replacing all the plastic/nylon timing chain guides including the ones behind the timing cover.

Its normal for the head gaskets to have rusted like that by now.

Re leak down tests - see here M119 Cylinder leak down test results - lessons learned! | M119 Engine

It's very common for small particles to upset the results of a leak down test.

Did you do a compression test?

Or a just a leak down test? And is where you heard the leak yeah?

Definitely take the heads to a machine shop have them clean and inspect them and test the valves too. Put a set of valve stem oil seals in whilst in there.

Been there done it myself so I'm telling you to do what I have already done



Only use genuine MB head gaskets from dealer.

And you MUST confirm the correct part numbers based on engine and vin number. There are at least 3 different types for m119 and my dealer ordered the wrong ones first but took them back as it was their mistake!