Author Topic: I may have stuffed up my head gasket  (Read 3138 times)

220sebCoupe

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I may have stuffed up my head gasket
« on: July 11, 2015, 07:56:19 »
Hi all

I have recently re-newed and installed the head on my 220 seb. I did it myself with some assistance for the heavy lifting and I don't claim to be a professional, just happy to tinker and I've done a few heads in the past. I may have stuffed up the head gasket though. I did the initial tightening of the head when cold (obviously) and then I missed the step about retorquing again on initial warm up. I retorqued the bolts at 500 miles and have been enjoying the car thinking nothing more of it.

Today, however, it is only running on 5 cylinders with the spark plug in number 6 fouled by oil. I changed it out and the car ran fine again, went for a drive of about 10 miles and the plug fouled again, back to 5 cylinders. having a proper look at the area around cylinder 6 I can see an external oil leak coming from between the head and the block at the very rear of the engine and I suspect the same leak is going internally and fouling the plug. I only suspect this rather than a failed cylinder as the compression was ok only a few weeks back. there is a little bit of oil weeping from the front of the end near the distributor as well

A couple of photos attached, can anyone tell me if I've stuffed the head gasket or if having a go at tightening the head bolts again might be useful?? anyone come across an external oil leak like this before?

Thanks in advance
I do love Mercedes Engineering, but why did I buy a 'cheap' project car, that was never going to work!

220sebCoupe

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Re: I may have stuffed up my head gasket
« Reply #1 on: July 12, 2015, 03:46:34 »
Im also wondering if taking out one bolt at a time and making sure there is no oil lurking in the bottom of the thread is ok, as in take one out, clean any oil and then replace and torque back down to the 90nm required or if removing the bolt completely is a big no no?

Its possible that there was oil in the base of the thread and ive tightened against the oil, just not sure about this one. Not the end of the world to pull the head off again and replace the gasket all together.

Dont want to make matters worse if the gasket is salvagable, and i'm feeling very out of my depth all of a sudden.
I do love Mercedes Engineering, but why did I buy a 'cheap' project car, that was never going to work!

Paul & Dolly

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Re: I may have stuffed up my head gasket
« Reply #2 on: July 12, 2015, 08:10:36 »

Does your car have an automatic transmission ?

Paul
Paul (located in Cardiff - Wales - UK)
1967 Early 250 SL (Auto) White
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220sebCoupe

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Re: I may have stuffed up my head gasket
« Reply #3 on: July 12, 2015, 12:26:34 »
Yes, but i dont think its a leak from the trans vacuum line, this is engine oil im sure.
I do love Mercedes Engineering, but why did I buy a 'cheap' project car, that was never going to work!

220sebCoupe

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Re: I may have stuffed up my head gasket
« Reply #4 on: July 12, 2015, 23:31:38 »
Hi fosdike

bottom line is I'm removing the head again. I took it off the first time due to a burnt exhaust valve on cylinder #2. Had the head reconditioned and reinstalled it myself. I had the injectors cleaned at the same time as I suspected that cylinder # 2 injector was not working properly leading to lean running in that cylinder and the burnt valve. I had the valve clearances checked by an experienced mercedes mechanic and he re-calibrated the fuel pump at the same time. It had been running quite well prior to this plug fouling episode. I checked compression following the re installation of the head and they were sound, not like brand new, but sound and consistent across the cylinders.

I've decided to pull the head off again as when looking at it all on Sunday on a cold engine, I had coolant leaking from the head gasket as well as the oil going out the back, so I'm suspecting a gasket failure. I'm putting this down to my incompetence when putting the head back on. I may have either damaged the gasket or I didn't do the head tightening sequence correctly. I didn't do the stage of initial warm up and retorque straight away, I don't know how I missed this stage, but I was thinking at the time that retorquing the head was done after a few miles not straight away. Just stuffed up I think. For the sake of $130 for a new head gasket and a few hours of my time, I'm going to give it another go. And while the head is off I will be able to see if any real damage has been done to cylinder number 6. It's possible that everything is fine and the oil control ring has let go, but with the coolant leak coinciding with oil out the back, I'm suspecting that the gasket has failed somehow - could be wrong, will let you guys know.

photo of coolant leak
I do love Mercedes Engineering, but why did I buy a 'cheap' project car, that was never going to work!