Due to oil in coolant, I need to replace head gasket in my 85 300D with 252,000 miles on it. The car is otherwise in great shape, and I expect to run this car for another 250,000 mi. or more.

I would like to do the job myself, but I have never removed a head before. However, I have done many other difficult repairs and feel that I can do it (in my driveway, no garage).

Once I remove the head, I should probably bring it to a shop for valve work, checking for warpage, replace valve guides, etc. The problem with this option is finding a reputable shop that knows what they are doing, and the down-time for the vehicle, and high cost.

Here is another option that I am considering, and would appreciate any comments on this.....I can buy a reconditioned head from Performance Products for $895 plus shipping and core charge. They say that their heads have been resurfaced, pressure tested, magnafluxed, new valve seats cut, new valves and springs installed, new guides honed to size, timing and cam bearings inspected and replaced if needed. These heads are reconditioned by a company called "Metric Motors" who have worked exclusively on MBZ for over 20 years, and they use OEM parts and done to the standards of MBZ (sounds good to me!!!)

By getting the reconditioned head, I could realistically do the head gasket/valve job in one weekend (even one day!!) for about $1,000.

In my vehicle currently, I get good compression (300psi+) in each cylinder and car runs great, and does not consume oil, so I dont really need head work. But I suspect that at some point, valve guides will go, and valves will need touch up. Even though the car runs great now, it doesnt make sense to me to simply re-install head without any head work. (cheap but not to smart, given that I want to run the car for another 10 years!)

This is my daily driver so down time is an important factor....also money is an important factor.

My questions are:

1) does anyone have any knowledge/experience about quality of Performance Products' reconditioned heads??

2) I do have the tool for removing the 12-point head bolts, and I am familiar with tightening sequence, torquing, etc. I have never removed a head or manifolds on any of my cars. How difficult or easy is this job...my sense is that it is fairly straightforward.

3) What do you do with the timing chain during head removal....do you remove a link, secure it with wire? when removing head?

4) on a 300D, are there any special tools, pullers necessary for the job...I thought I remember reading that there is some type of pin on the chain guide or something that needs to be extracted ???

Sorry for the long question, I would appreciate any feedback from someone who has done it...thanks in advance

Mark

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1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)

Mark,

Are you quite sure that the coolant/oil problem is the head gasket? Did the engine make any noise and then suddenly start the coolant/oil mixing?

Assuming that the problem is indeed the head gasket, with 300 pounds compression, I expect that the valve job, guides and head gasket would fix up the engine quite nicely.

I have no reason to believe that the Performance Products head is not okay, but that's a pricey way to go. I use an expensive machine shop and my head work was under $500.

Anyway, you said you knew about torqueing a head, are you aware of the two 90 degree angle torque steps for the MB engine?

You will only need to pull one pin as I recall. There is a puller for this but you really don't need it. If you have a long bolt that will thread into the pin, put a nut and washer or something under the bolt and tighten down, this will pull the pin.

You merely need turn the engine to TDC with the camshaft mark aligned with the cambearing stand mark which is on the front cam bearing stand about 45 degrees toward the drivers side. Leave the engine in this position while apart. Once the cam gear is off, pull tension on the chain and loop a piece of baling wire around it to tie it off somewhere(for city people, a coathanger makes an acceptable substitute for the high tech baling wire ) Then when removing the head, try to keep tension on the chain while holding the wire. Pull off the head, pull the wire through and tie it off again to hold tension.

If you lose the chain, it's not totally catastrophic, you can fish it out, but it will then require retiming, or at least checking the timing of the injection pump. If it comes down to pulling the injection pump, it will be a rather large job though.

With an engine of such good compression and using no oil, a fresh head will make a near new engine out of it.

I still have concern about the coolant/oil situation. A blown head gasket on these iron head, iron block engines is not common.

Best of luck,

Remember, the head is CAST IRON and reall, really heavy. I would make sure you have an engine lift or powerful hoist in place FIRST. Trying to do this job alone (without lift etc.), you WILL hurt yourself and possibly damage your head/ block/engine compartment/accessories. I must stress this. It took two people to remove the small (in comparison) alluminum head from my BMW project car. Weighed 90lbs. Very difficult to lift and position while leaning over engine compartment. I wouldn't dream of dooing your job without a crane!

Otherwise good luck and work safely.
Dr. D

So here's the cheap and lazy approach:

1) Retorque the head bolts. Observe for improvement. Has the advantage of being both cheap and lazy, since you don't have to remove the head.

2) Replace the head gasket. Observe for improvement. At least its cheap.

Only then consider a refurbished head. You should be able to get 300K + miles without worrying about a valve job.

I have seen engines seal right up with just the head bolt retorque. This includes compression leaks into the cooling system, which is VERY high pressure. Your oil into the cooling system is a significantly lower pressure situation.

Ken300D
"Cheap and Lazy"

The head bolt tool can be found at any good auto parts store. It is called (I believe) a 12mm Triple Square.

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Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)

I respectfully disagree about using a crane or helper for this cylinder head. I just took a five cylinder head today for shipping. In the crate that I made, it weighed 104 pounds and 7 ounces. I would estimate the crate at five or ten pounds.

I was able to change it on my daughter's car last Winter by myself, and it wasn't that bad. I have a walking beam in my shop, but I would have had to move things around at the time to center the car under the walking beam, so I just handled it. You have to set the head on the engine diagonally, then pick up the front to maneuver over the timing chain and guide, that's the hardest part.

To me it would be more trouble to mess with getting a cherry picker or whatever contraption to raise the head, than just muscling it in place.

Also, I wouldn't bother retorquing the head. Because of the way the stretch bolts maintain tension, I can't imagine this working on this engine. On an engine without stretch head bolts, maybe it would be worth a try. With the stretch bolts I think it would be a waste of time.

But, if you do decide to retorque, remember that you will have to loosen all bolts, then torque in sequence to 34, then in sequence to 52 and then in sequence 90 degrees, then in sequence another 90 degrees. Given that the bolts can only be stretched 2 or 3 times before they surpass specified length and have to be replaced, I would not take the risk of using up my head bolts. They are about $4.00 each or something like that. There must be about a couple of dozen of them or something.

On the other hand, if you can ensure that the head gasket is your problem. This engine will respond well to a valve job including guides. Much of the integrity of the engine is in the cylinder head. If the cylinder head is up to par, and there is not excessive liner wear, you will have an engine that runs extremely well.

Your comments were very helpfull. I have a complete set of Mercedes shop manuals, often very hard to follow. Thanks Larry and others for the experienced perspective.

I wouldnt do this job until next spring or summer, and I will monitor the situation until then.

The engine shows none of the performance problems you would ordinarily associate with a blown head gasket..it runs like a charm (except for the typical minor rocking at idle). I think I have a "weeping" head gasket...not a "blown" one. I have always adjusted valves and changed oil religiously....conceivably I could run this car for another 250,000 without needing head work (unrealistic??). I'd hate to do all this work because of a minor (?) problem.


I would very much like to try re-torquing the head this weekend, flush cooling system and put in new antifreeze.

As long as I am not getting coolant in the oil (which I have no indication of), I can deal with a tablespoon of oil each year ...just flush and change coolant yearly...and run the car. But, I would hate to have a subtle condition which causes major damage within a year or so (corrosion of rings, etc.??) due to small undetectable amounts of coolant in oil. I'm not sure what the possible consequences would be of just running the car like it is.

Well, first things first...I need to re-torque headbolts, flush/replace coolant, and drain radiator every month or two to see how much (if any) oil shows up.

Question: Is there a special torquing technique for re-torquing the head. I assume that the standard torquing procedure is intended for a new (un-compressed) head gasket, but do follow this procedure for re-torquing???

Also, before re-torquing, I would probably plug in block heater overnight (since we are into cold nights here in New England) just to warm things a little and make things more "pliable and forgiving".


Thanks again.

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1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)

Larry, you beat me!!! I wrote my last response at the same time you sent yours!?! You answered some of my questions real time as I was thinking them up!! OK, what am I thinking now??

You're correct...I'm not sure what to do now.....maybe just flush and replace coolant, and monitor.

The oil in coolant problem developed since I started using synthetic oil (amsoil 15-40 diesel full synthetic), and my gut tells me that is the cause (??). I have switched back to conventional Rotella, although previous posts on this subject say this will not reverse the condition. Maybe I should use some real cheap 50 weight stuff with a lot of wax, although not good with winter coming!

My common sense tells me, if it walks like a duck.....etc. etc....I have a leaking head gasket, and I should combine valve job/sleeves etc. with head removal, gasket replacement...probably will do this next summer. With a couple little kids, I find that I just dont have the time to do this stuff, even though I really enjoy it. What is a fair price for a reputable shop to do the whole job...basically a valve job....including removing & replacing the head???? $2,000 yikes?? also, probably a full week or more without the car.

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1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)

Mark,

Are you sure it's motor oil and not transmission fluid in the coolant?

Sixto
91 300SE
81 300SD

The oil in coolant is dirty and brown/black, not clean and red....must be engine oil.

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1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)

I've got the same car with 230k miles. I'll be durn if I would pull the cylinder head off if the car is running good and I have that kind of compression. Change the coolant, run the car a couple weeks and see what your oil and transmission fluid level is doing. I would be more inclined to be looking at the radiator than the head if it is running as good as you say. Just because it ain't red does not mean it is not tranny fluid.
The head can be removed without the lift but plan on eating your wheaties that morning. When I recently removed the head on the 240D I had my left foot on the top of the passenger side coil spring housing and my right foot on the top of the front bumper, my butt on the front right fender with a friend holding the timing chain. Picked that sucker up and took it right over to the bench.

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Jim

You know, I just went out and got a sample of coolant, brought it into the house, sat down and really looked at it closely under good light.....It does look red!!! Praise God!!! you mean all I have to do is replace the radiator????

The oil in the coolant looks dirty though....could it be that sediment/corrosion particles from the coolant system get caught up in the tranny oil making it look like engine oil??? Reddish?..Brownish?...very similar!!

Based on this observation, I'm leaning toward the cross-connection in the radiator between coolant and tranny fluid.

How do I definitively check this???

(Thanks again to all)

Mark

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1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)

I checked PartsShop radiators....Nissen @$215, Behr at $360......is the Nissen good, or would you folks recommend OE Behr??

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1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)

Mark,

I hate to bring possible bad news into your good news discovery. But you should be aware of this as soon as possible.

I expect that the ATF is getting in the coolant and not the other way around. I expect this is the case because there is much more pressure in the ATF cooling lines than in the cooling system. However, when the vehicle cools off, it could be putting antifreeze in the A/T. Antifreeze is absolute poison for the clutches in an automatic transmission.

I would recommend that you remove the radiator and take it to a radiator shop for testing before buying a new one. I'm sorry, but I have no experience with the nissen, or whatever brand. Behr is the original equipment MB radiator, of course, you probably know that.

Once you have tested and replaced the radiator. Change the ATF and filter as soon as possible. Your transmission is the second or third most expensive component in your car, don't risk it's health.

BTW, this doesn't surprise me. I would have been shocked if your perfectly good running cast iron 617 motor had blown a head gasket with the only symptom being oil in coolant.

Best of luck,

On this age car I do not think the brand of radiator makes alot of difference. Don't forget to change the automatic transmission fluid and filter while you are at it. You will need the ATF filter, pan gasket and crush rings (one for the pan and one for the torque converter). Don't overtorque the pan gasket or you will get to replace it again. I can't say I have ever had any problem with the Nissen radiator - I think that is what I am running in my 300D now.

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Jim