Still leaking after head rebuild

[Marrs]

My shop rebuilt the head on my 220seb and it is again leaking in essentially the same spot. I read through the old posts on the W113 archive about similar issues on Pagodas and the various remedies and work arounds tried. I would like to know if anyone has an update or more recent experience regarding the causes, potential remedies and so on. Also, when a head gasket is being replaced, is it common or even expected for the shop to plane or square the mating surface on the block or is that only done on a full engine tear down? I know they are supposed to check that it's square, but if not what is the procedure to correct when only doing a head gasket job? We are going to verify the leak isn't from somewhere else and migrating along the mating line, but if it is still leaking I'd welcome your opinions.

[Jack Jones]

If this is a case of the block not being true, the shop completing the task should have checked it with a precision straight edge the same way a head is checked. In order to deck the block you must remove the engine and perform a tear down since the decking process will introduce filings through out the block and must be cleaned completely before reassemble. Not cheap but neither is spending money to rebuild the top end and not completing the job. If it is indeed the block surface, you should have been advised and quoted so you can make the decision.

[ja17]

Where is it leaking?

[Marrs]

Where is it leaking?

The leak is on the spark plug side in about the middle/rear of the block right along the seam where the block meets the head. It's just below the pipe but the pipe does not appear to be the cause.

[Marrs]

Not cheap but neither is spending money to rebuild the top end and not completing the job. If it is indeed the block surface, you should have been advised and quoted so you can make the decision.

When I asked if they checked the block when they did the head work they said yes, but at the time there were no remarks made to me that it needed any work and they went ahead with the new head. Hopefully that means it was within spec, otherwise I can't imagine why they would proceed in such a way. They are looking at it this week so I should have an answer soon as to why and how.

[Benz Dr.]

I did a block with all of the pistons installed and it worked out OK. This was on my own car and not a customer car. The whole bottom end had been recently rebuilt and I left the rad cap off which caused the engine to overheat and that warped the block.
We filled the chain case with rags and I left the chain installed on the crank. I wouldn't advise this procedure and I'm only noting that it's possible to do this in some cases. In the case of old parts I would take it all apart. I might add that I spent a lot of time prepping the block before I took it to the machine shop and I did a lot of careful cleaning after I brought it back.

[Cees Klumper]

Is it possible that the leak is caused by the 'rocker support towers' that are not always secured into the head leak-free?

[Marrs]

Is it possible that the leak is caused by the 'rocker support towers' that are not always secured into the head leak-free?

Could you go into a bit more detail for me, such as the specific relation/cause to a leak? Thank you.

[Cees Klumper]

These towers apparently are screwed into the head, but the threads go clear through the head. So if they are not sealed peoperly, oil will seep through and leak down, and can appear as leaks from the spark plugs or other places. I recall this from contributions from others like JA17, not my own experience.

[Benz Dr.]

Good point Cees but I believe this is a coolant leak.

[ja17]

What head torque spec did they use and did they do a re-torque after first warm-up?  If it were mine, I would over-torque it to 70 ft./ lbs. ( original spec. is 58 ft. lbs. )before tearing it down again. Be sure to remove the radiator cap before doing a re-torque.

[Marrs]

What head torque spec did they use and did they do a re-torque after first warm-up?  If it were mine, I would over-torque it to 70 ft./ lbs. ( original spec. is 58 ft. lbs. )before tearing it down again. Be sure to remove the radiator cap before doing a re-torque.

Not sure of the torque spec applied but the head was from Metric and my shop tends to be by the book so probably the spec you quoted (but I'll ask), and no re-torque was done, I asked specifically about that. He said he "does not like to do that" so I got the impression there was a specific reason why, again maybe just going by the book.

Cees: Thanks for the clarification, but yes, this is a coolant leak. Useful to know however!

[Benz Dr.]

What head torque spec did they use and did they do a re-torque after first warm-up?  If it were mine, I would over-torque it to 70 ft./ lbs. ( original spec. is 58 ft. lbs. )before tearing it down again. Be sure to remove the radiator cap before doing a re-torque.

I wouldn't do that. You can go about 5 foot pounds over the standard torque spec but that's about it. Excessive over- tightening can pull the metal in the block and warp it. I would definitely try a re-torque and see what happens. I've had the odd leak that wouldn't go away and I cured it with radiator stop leak. After it stopped I drained the rad and put regular coolant back in. Still dry several years later.

[Marrs]

I wouldn't do that. You can go about 5 foot pounds over the standard torque spec but that's about it. Excessive over- tightening can pull the metal in the block and warp it. I would definitely try a re-torque and see what happens. I've had the odd leak that wouldn't go away and I cured it with radiator stop leak. After it stopped I drained the rad and put regular coolant back in. Still dry several years later.

Personally I hate using any sort of stop leak product on a car, but I am not judging your preference in any way, but I like to find and correct the problem by replacing with a new part or service. It's far more costly and often frustrating, but I look at this car as a mistress who requires special attention.

Also, as an update to this thread, we are looking at a couple of possibilities on the leak presently and I will report the solution as soon as I have a final, definitive answer.

[ja17]

The BBB says to re-torque after first warm-up then again after some miles (500).  The threads in the block must be clean and the bolts threads  should be cleaned and lightly oiled during original assembly to get accurate torque. Do the re-torque on a warm engine and don't forget to remove the radiator cap.

[Benz Dr.]

Personally I hate using any sort of stop leak product on a car, but I am not judging your preference in any way, but I like to find and correct the problem by replacing with a new part or service. It's far more costly and often frustrating, but I look at this car as a mistress who requires special attention.

Also, as an update to this thread, we are looking at a couple of possibilities on the leak presently and I will report the solution as soon as I have a final, definitive answer.

How badly is it leaking? A small seeping leak may seal off after a bit of driving and if it's a steady drip the block is likely warped a bit. Anything more than a .003'' warp on the block or head and it won't seal up.

Were you intending to do a full rebuild before you removed the head? I ask because a warped head and block would most likely be caused by over heating and in that case you would see an external leak even
 before the head was removed. If you didn't see any leaking there would be less reason to think the block was warped before it came apart.

Using stop leak on small seeping leaks is OK in certain cases. Not everyone wants to spend on a full rebuild and sometimes that's the only recourse. I've done a lot of valve jobs and they never leak if the block is straight. I always ask my machinist how badly the head was warped ( because they always are ) as that can point to over heating. If it's warped like a banana, then I really start looking at things. A quick look at the top of the pistons will tell you if coolant is leaking in to a combustion chamber.  

[ja17]

Dan, I too have successfully used stop leak as last resort to tear-down. Seems to work in a lot of instances.

[Benz Dr.]

Yes, it will. It's a practical solution rather than getting into a lot of work or money.

[Marrs]

Thanks again for your continued assistance, I wanted to reply when I had new information. The shop did retorque the bolts and they turned about 90-degrees, they were never retorqued after the head was rebuilt. There is a TSB from Mercedes-Benz clarifying that this should be done done after head jobs, so a retorque is apparently the correct way now.

In my case, after they retorqued and gave me the car back, I still saw the same leak in the same area. I took the casr back and left if for them to check after sitting overnight and eventually the shop was able to determine that there was a tiny pinhole leak in the connector on the pipe the comes out of the block on the middle/rear of the spark plug side of the head. This leak would not present under pressurization, but only after the car was warmed fully. The hole itself wasn't even a hole but more like layers within the metal had flaked and separated on a microscopic level invisible just by looking, so my mechanic basically saw what just looked like a drop hanging on the bottom of the pipe when it was actually the source. They checked and replaced with one from another engine they had, it was in excellent shape, and now things appear to be corrected.

If anything, I feel validated that I wanted the shop to see the leak I was seeing before they did the head job, in this case they would have done it and the leak would still remain, so I am glad we avoided that mess. Your advice has been an absolute help and I thank each of you who took the time to respond.