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Old 03-14-2002, 11:15 AM
pmizell's Avatar
Benz Zealot
Join Date: Jun 2001
Location: Houston, Texas
Posts: 838
Head gasket replacement a success. (sort of)

Well, I finally finished this task. Let me just say that this job is not for the casual DIY'er -- you WILL run into a snag or two along the way that will test your patience. Some that come to mind are reinstalling the chain tensioner (trying to screw it in with the spring behind it is a pain), mating up the 2nd exhaust manifold with the pipe was difficult, gaining access to the intake manifold support brackets is tough, replacing head while inserting it into the small coolant hose was a pain, and doing the two 90 degree torques on the head bolts was a workout in and of itself. (my arms are sore!) Also, if your car is somewhat older like mine ('91) you WILL break a brittle plastic piece or two along the way, guaranteed.

Now to my problems -- while my engine is not overheating, the coolant overflows from the overflow tank when I turn the car off. I don't think it's the radiator cap because I just replaced it about 6 months ago, so I think it's keeping pressure in.

Also, as I suspected I actually had oil leaking from two places prior to job, the head gasket and somewhere up front -- now more pronounced since extra pressure is being diverted there. I sealed the front cover very well, what else is left besides that and the timing chain cover? How likely is it that this area would bust a leak? One caveat: I COULD NOT do the complete second 90 degree torque on the front two head bolts for some reason -- they simply would not budge after about 15 degrees or so.

Thanks again to everyone who lent their advice on completing this job! ($350 for valve job (guides and seals, grind), resurface, clean, remove and replace cam and rockers)

**edit -- the front oil leak was located: apparently I rolled over the front U-shaped gasket on front cover. Going to try to seal it from outside with the black sealant, if not then I'll remove then reinstall.


'91 300E, 208k miles

Last edited by pmizell; 03-14-2002 at 12:09 PM.
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Old 03-14-2002, 12:45 PM
94 E320
Join Date: Jun 2001
Location: Fairfax, VA
Posts: 437
those are some great pics!

maybe you should make a webpage on what you did and stuff...i know you'd have a lot of visitors just to see what the heck is done

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Old 03-14-2002, 01:01 PM
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Join Date: Jul 2001
Location: Western Michigan
Posts: 1,080
Hey, Paul:

What is that blue oil filter?
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Old 03-14-2002, 01:42 PM
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'94 S500: only 793 sold!
Join Date: Mar 2001
Location: San Diego, CA
Posts: 1,929
Nice job and good pics!

I've tried to see myself doing that job but the image seems to blur badly!

I no expert here but my tech says that those head bolts should have been replaced. They probably were stretched and possibly bottomed. If so, it will leak, if not now then later.
Regards . . . . JimF
'94 S500 Cpe

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Old 03-14-2002, 02:45 PM
pmizell's Avatar
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Join Date: Jun 2001
Location: Houston, Texas
Posts: 838

That's a Walmart-brand oil filter (Supertech) -- $1.95. Hope I didn't just start a "best oil filter" debate.


I did use new head bolts -- that's why torquing them down is so difficult because you're stretching them to their limit.


'91 300E, 208k miles
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Old 03-14-2002, 02:51 PM
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HaHa. I was wondering as most of the OEM filters are black.

Does the Wal-Mart filter have the anti-drain valve?
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Old 03-14-2002, 05:20 PM
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Join Date: Jun 2001
Location: Houston, Texas
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I didn't know the OEM MB filters had that feature but I believe this one does, as no oil seems to drip from it when I lift it out.


'91 300E, 208k miles
"smoke silver", cream interior
Hella Euro headlights w/amber strip corners
Sportline, 8 hole, '15 rims, 7J
'94/'95 tail lens'
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Old 03-14-2002, 05:29 PM
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smoke gets in your eyes
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When the cam's in place, do valves extend past the head gasket surface? I'm surprised you can lay the head on a flat surface as you did and not bend valves.

91 300SE
81 300SD
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Old 03-14-2002, 05:29 PM
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Location: Western Michigan
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It could be that the oil has already drained back into the engine when you took the filter out.

You can see it by just looking at it. Look into the center hole. Do you see a spring loaded little plate in there?

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Old 03-14-2002, 07:58 PM
Live to Learn
Join Date: Mar 2002
Location: Raleigh NC
Posts: 145
The front head bolt holes are blind holes,meaning they have a bottom.A lot of times when I do this job,I have to use a vacula to suck oil out that settles in the holes when the head is removed.If oil has gotten into the holes,the bolts could be hydraulic locked.If this is the case,the head is not properly torqued and could leak or even worse,warp.
Its worth checking.
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ASE Master Technician
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Owner of "Behind the Star Inc."
Raleigh NC.
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Old 03-14-2002, 08:08 PM
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Join Date: May 2001
Location: Charleston, SC
Posts: 237
Congratulations PMizell

I may be contacting you for details questions when I attempt this hopefully in the distant future.

How would you rate difficulty compared to other significant mechanical tasks?

Great pictures. Head looked terrific after valve work. What was the report on pre-rework head condition from machine shop (re: valve guide condition, etc.)
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Old 03-14-2002, 08:21 PM
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Join Date: Jun 2001
Location: California
Posts: 327
Great job Paul!

Let us know if the coolant overflow persists. Hopefully it's just "burping" itself.

Since those headbolts are a one shot deal, you might want to replace the front two. You could grind a very small amount off of the end (like 0.5mm) to ensure that they won't bottom. It's possible that you got some gasket material in there and it's probably really jammed in the bottom of the blind threads now.

What did you decide to do with the dropped washer? is it still in the bottom of the pan?

Also, please comment on the before/after power characteristics.

Thanks for posting the great pics.

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02 E430

Experience is something you don't get until just after you need it.
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Old 03-14-2002, 08:37 PM
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Congrats. for that major DIY job.
I just had the very same job done last week (valves, camshaft, lifters, etc) by a pro. (i.e not dealer). You saved yourself quite a bit of money but my knuckles are certainly less painfull than yours.
My car now drives like a much younger one and it seem I found some 25 to 35 HP. You don't realize the slow/gradual deterioration in power and smoothness over the years.
I also replaced dist. cap, rotor, spark plug wires (spark plugs too), had the injectors cleaned, etc etc. Big bill but big improvement.
Congrats again
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Old 03-14-2002, 09:38 PM
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Location: Houston, Texas
Posts: 838
BWB: Thanks for that advice. I will probably buy 2 new head bolts and re-torque them down, just for peace of mind.

Carolina: the machine shop said that the guides were "falling out" of their chambers when they pulled the valves , and he said the seals were in pretty bad shape as well. The guy asked me if it was visibly burning oil (blue smoke) and I told him no, that it ran just fine actually and he couldn't believe it. With so much oil pouring into the coolant I could never tell how much, if any, the engine was actually burning. The head was warped slightly, but not enough to be thrown into the oven to repair -- resurface is all that it needed. Feel free to email me with any questions if you decide to tackle this job. It is not difficult if you have a good set of tools and know the minor pitfalls to avoid. I had the luxury of having the official MB shop manual AND 124 CD set to guide me and I might do a how-to on this job if I get the time.

Dennis: Thanks! Yes indeed it was the system just burping itself. It seems now that the coolant system is much more sensitive to the exact coolant level. Previously I would fill it over the high mark with no problems. Apparently the ebb and flow of the coolant was not very significant having oil mixed with it. Now there's an exact level that I must keep it at. Regarding the head bolt washer, I left it in there. After finishing, I manually cranked the engine a few times via crank bolt to make absolutely sure it was not near any gears or chain -- then I pulled the coil and hit ignition a few short times to try and manipulate it down further if it was still caught on something. Then I started her up and I've had no problems so it must be in the sump:p As far as power goes, absolutely an improvement. It seems I've gained more torque at less RPM's and kickdown is ALOT faster to respond. I haven't really driven it hard yet however as I don't want to mess anything up .... yet.

Jackd: I know what you mean by the increased power and smoothness. I can actually feel and hear the increased compression with the engine completely sealed now. It is amazing.


'91 300E, 208k miles

Last edited by pmizell; 03-15-2002 at 10:06 AM.
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Old 03-15-2002, 02:53 AM
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It's about time Paul !

I thought you were right behind me with my head job. I was wondering if you had a major problem. Funny how great minds think a like or do the same stupid things. I also rolled over my gasket and oil leaked down arount the dist cap and I thought I didn't seal the cam well enough. Also had a little problem with my water level for the first week or so. I went back and retightened all my hoses that I replaced or put back on. Don't forget the one on the back of the head near the fire wall. I changed oil at five hundred miles TO GET OUT ALL THE JUNK OUT. My dip stick doesn't Move! I'm not getting quarts per mile any more. While I was under neath addressing the oil leaks I discovered 205K worth of steering linkage was shot. Went to Fastlane and replaced both tire rod assys, center link and shock dampener for under $200 dollars. Auto Zone lent me a tie rod pickle stick which was a great help. I retorqued my head bolts down again ( local Benz mech measured them and said they were still ok. If you pull those bolts off to clean your holes, get some expert advice on how to retorque the head down. You might have to untorque the rest of the bolts to resequence them.
Best of luck , keep me posted.

Mike V
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