i'm in the process of replacing the head gasket on my 1991 300 2.5l diesel and what a job/nightmare ..... for 200K miles the motor looks amazing good .... NO ridge on piston walls cant feel one @ ALL vales look good and not burnt .. i have heard on some motors to use only new head bolts becuz they stretch ...is that the case on mercedes diesels, anyone know ....i have to replace a few becuz stripped head ... other than that any suggestions BEFORE I PUT IT TOGETHER ???

Personally, I would replace them. Did you have the valves and seats ground?

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Milan Brown 1979 240D, rebuilt OM617.952 turbo diesel, rebuilt 722.315 transmission (my only daily driver)

Instagram: @maximed93

no i didnt think they needed it ...but maybe a good idea ???

I have replaced OM60x head and gasket a number of times and never once replaced the head bolts. You can always measure them but I doubt they would be stretched.

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I feel it is not worth the $ to NOT replace them. It is a lot of work to do a head gasket job, and replacing the bolts is "cheap insurance". You don't want to find out the hard way that a bolt was stretched too much half way through the job, or a short time later when the gasket leaks again. I also would not put a head back on that has not been serviced (surface machined, valves ground, stem seals replaced). Again, it is a lot of labor and expense to do twice. Best to just do it right the first time. Just my opinion tough, YMMV.

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I just replaced the head and head gasket on my Om603. I had 2 sets of Head bolts and they all measured well within spec so I reused one set. The car is up and running with no issues at all.

Opinion.

I have noticed in the last 3 years there has been a decline in the number of members that want to own a Manual for their Cars.

It seems clear that if the manual has some spec on the head bolts and tells you how to determine if the Bolts can be reused you could use that info to decide if you want to reuse the head bolts or not.

If you don't have the means to measure to tell if they are out of spec or not one would think the best choice would be to go with new ones. (However, there has been some complaints about aftermarket head bolts.)

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84 300D, 82 Volvo 244Gl Diesel

thanks for the advice guys .... DAMN right its a lot of work the reason im even doing this is becuz the car is in mint condition ... came from florida and has the orthopedic seat upgrade bought it with blown turbo .... i agree its cheap insurance AND doing the heads . ... they just looked in good shape will do that tooooo

So is there a reason why you're R&Ring the head without consulting the service manual? Do you even know the bolt tightening pattern or the torque sequence? If you're winging it, you'll be back sooner rather than later, probably with a warped or cracked head. Everything you could ever need or want to know about the bolt reuse and acceptable stretch limit is part of the head R&R writeup in the FSM.

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Current stable:
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1983 500SL 120K (SLoL)

Black Sheep:
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Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
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While the head is off I'd get the valves ground and as Roll Guy said get it surfaced and checked for warpage. I'd also have the machinist measure the head bolts to see if they meet specs to re-use. The valve springs can be measured too.

I agree to get a manual for guidance.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Only replace if they exceed max permissible length. I've yet to fine one MB stretch bolt that exceeded spec and always reused.

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CENSORED due to not family friendly words

thanks guys for all the help YES i do have the service manual with all the torque settings etc.. .... i'm crazy enuf to to do this ... NOT stupid lol

i'm crazy ... not stupid to wing it lol

Surfacing the head - don't do it unless you have it measured and the FSM specs say that it needs to be surfaced. Understand that the FSM says you'll need to have a particular amount removed, and then use a thicker headgasket to make up for the lost material.

Re-use of bolts is your call, I've done it both ways. If they are not stretched beyond the FSM limit, I'd re-use them.

I would highly recommend that you replace the valve stem seals.

If you do have a shop check the head for flatness, have them also check the valve guides. Once again you will need to give them the specs from the FSM so they know what they are measuring.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

Earlier I was going to mention. Depends somewhat on the overall condition of the car. Plus if a decision is made to do the head. Try to make sure the place you choose is competent. Perhaps even getting an opinion on where the Mercedes local dealers sub out their head work from them.


Personally I would not resurface the head if it is flat enough already in the shops opinion. I would carefully also check the blocks surface myself. If you really understand head bolts and they are under the maximum allowable stretch for reuse. Mercedes probably has a small safety allowance as well in their measurements. This then depends on cost of the new bolts. I always put a new set in when they were cheap on engines. Those days are probably gone. It just seems to be the way more often today than not.

For what it is worth although the valve seals are not as critical as on Mercedes gas engines. I would want them sourced from Mercedes specified as well.