91 300d 2.5l head gasket replace ... head bolts ??? - Page 2 - PeachParts Mercedes-Benz Forum

netpro · #16 07-15-2019, 11:09 AM

Quote:

Originally Posted by barry12345

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 already in the shops opinion. I would carefully also check the blocks surface myself.

thks YES i have a shop in mind has been in business over 30 years and highly recommended like i mentioned the car is in perfect condition and body , interior like new, with the orthopedic seat upgraded interior so well woth fixing came from florida i think i'll use new bolts not much $$$

tjts1 · #17 07-15-2019, 12:14 PM

I didn't resurfaced my om603 #17 head mostly because I would've had to pull the prechambers. The head measured flat so why bother.

Frank Reiner · #18 07-15-2019, 02:26 PM

np:

Re: Head resurfacing
Suggest that before you seriously consider resurfacing, do this test of the head on the bench:
> Remove the cam followers from above the valves
> Reinstall the camshaft in the head & tighten the bearing caps
> Does the camshaft turn freely by hand? OR, Does the cam bind in the head?

If the cam is free in the head, the head is not warped, and resurfacing would be done only because of corrosion and/or pitting of the gasket surface.
If the cam is binding in the head, the head is warped. If the gasket surface is OK, DO NOT resurface. When the head is re-installed on the block the warpage will be relieved, and the cam will turn freely again. If the gasket surface must be resurfaced, a second machining operation will be required: align boring of the cam journals.

netpro · #19 07-18-2019, 08:00 AM

Quote:

Originally Posted by barry12345

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.

the shop ( very reputable ) said the head needs to be planed ..where the gasket was leaking is grooved .... what bugs me is u said i need a thicker gasket ... i already bought one from mercedes sources now its no good ??? how do i know its thick enough ... .what are the specs ...obviously dont want ot go thru all that trouble to find out its not good enough gasket .... help me out here

ROLLGUY · #20 07-18-2019, 10:25 AM

Quote:

Originally Posted by netpro

the shop ( very reputable ) said the head needs to be planed ..where the gasket was leaking is grooved .... what bugs me is u said i need a thicker gasket ... i already bought one from mercedes sources now its no good ??? how do i know its thick enough ... .what are the specs ...obviously dont want ot go thru all that trouble to find out its not good enough gasket .... help me out here

There is a certain tolerance that is allowable with the standard gasket. If the shop only takes off a couple thou, no problem. You can also get thicker prechamber seals, but they are only needed if nearly a mm is removed (they come in 1mm increments thicker).

t walgamuth · #21 07-18-2019, 11:05 AM

Agreed.

I have had five or six of these built by my local machine shop. He has always checked for warpage of the head and resurfaced for a better seal without resorting to a special gasket.

He also checks for twist on the block.

He then replanes the block so it is parallel to the crank. Again never enough to require a thicker head gasket. He does remove the prechambers and replace the shim for proper work.

moon161 · #22 07-18-2019, 11:47 AM

Quote:

Originally Posted by netpro

the shop ( very reputable ) said the head needs to be planed ..where the gasket was leaking is grooved .... what bugs me is u said i need a thicker gasket ... i already bought one from mercedes sources now its no good ??? how do i know its thick enough ... .what are the specs ...obviously dont want ot go thru all that trouble to find out its not good enough gasket .... help me out here

The machinist removes material say .010" (the wall of a soda can is .005") from the block, head or both to clean up the gasket surfaces and establish a flat mating surface with the appropriate finish & roughness. If there's a scratch, pit, erosion, whatever that's say, .015" deep, the machinist has to remove .015" from the whole head instead to get a flat surface that will seal well, and this might be beyond the allowance built into the design for a normal head gasket. If this is the case then (with 60x motors) there won't be enough space for valves & prechambers at TDC if (you shave the head) or for air, valves & prechambers at TDC (if you shave the block). To make up for it, you can get a thick head gasket, which it sounds like your machinist is saying you need.

moon161 · #23 07-18-2019, 11:59 AM

As for head bolts, if you get new ones, you'll have to take the OD of the head down a touch to fit in any of the counterbores outside of the valve cover. Doesn't matter where you get them. I used a cheap HF bench grinder.

Maxbumpo · #24 07-19-2019, 07:44 AM

Quote:

Originally Posted by netpro

the shop ( very reputable ) said the head needs to be planed ..where the gasket was leaking is grooved .... what bugs me is u said i need a thicker gasket ... i already bought one from mercedes sources now its no good ??? how do i know its thick enough ... .what are the specs ...obviously dont want ot go thru all that trouble to find out its not good enough gasket .... help me out here

The specs are in the FSM. Procedure 01-418. Print that out and provide to your shop.

Maxbumpo · #25 07-19-2019, 08:03 AM

Quote:

Originally Posted by Maxbumpo

The specs are in the FSM. Procedure 01-418. Print that out and provide to your shop.

Well that does not have the repair gasket spec. Now I can't remember where I read that. Maybe the Mercedes Electronic Parts Catalog (EPC)? Maybe I am mis-remembering info for the OM61x engines? Going to look in that FSM and let you know.

It would appear that as long as the head does not go below the minimum height, you can use your head gasket. I would suggest a call to the Mercedes Classic Center to check and see if a thicker gasket is available and what the dimensions are.

https://www.mercedes-benz.com/en/mercedes-benz/classic/classic-service-parts/