torque specs for 617 valve cover... 15NM or 25NM? Still leaks - any tricks? - PeachParts Mercedes-Benz Forum

bodyart27 · #1 11-07-2003, 10:42 PM

I noticed Thomaspin has 25nm:

http://www.pindelski.com/cars/W126/Valve_adjustment/imagepages/Pic00061.html

my shop manual showed 15nm

I'm still getting valve cover leaks after my valve adjustment. I put in a new genuine MB gasket and prepped the surface to be clean as possible. Still looks like I'm leaking.

Any tricks on this?

bodyart27 · #2 11-07-2003, 10:49 PM

OK, so quick orientation for this photo - injection side, near firewall, last injector on upper left. My question is - see that double hex head bolt kinda dead center and to the left? Can that leak? It seems to be (I just wiped it down - sorry). Is the only thing to do is screw it in tighter?

TN-W124 Diesel · #3 11-07-2003, 11:02 PM

if it is the valve cover leaking...I use a high temperature silicone sealant (RTV) and a gasket

#4 11-07-2003, 11:48 PM

You need to apply a thin layer of engine oil to all mating surfaces (Valve cover, head, and both sides of the gasket) to create a sealed connection much like with a regular oil filter gasket.

Kyle Blackmore · #5 11-08-2003, 01:35 AM

Bodyart27 that double hex bolt (XZN) is a head bolt , and I've heard of a trick with the 'stops' on the underside of the cover.Make sure they allow the gasket to squeeze down and compress enough to seal properly.My experience with these gaskets is they will seal IF the head and gasket and cover (where the gasket sits at least ) are cleaned almost to surgical standards. I clean as best I can with a rag and then go over the areas with Q-tips dipped in rubbing alcohol. I go 20,000 miles between valve adjustments without a leak

. Tighten the nuts down till you feel them 'stop' , that's the right torque

.

bodyart27 · #6 11-08-2003, 09:20 AM

I even buffed the surface with 000 steel wool... I re-torqued to the lower 15nm last night... maybe the higher torque was deforming the gasket. I just had oil running down on the engine I just cleaned

So that hex bolt that looks to be leaking - can I tighten it a little bit without warping anything?

below is an example of the surface prep on for the valve cover...

Kyle Blackmore · #7 11-08-2003, 01:21 PM

Shell , unfortunately once it starts leaking you have to take it off and start over

. The oil gets between the gasket and the head and tightening it down won't stop it.When you pull it off check the stops on the underside of the cover , there are 4 of them.If the cover has been overtightened these can get stretched. Turn the cover upside down and look down the edge , the stops shouldn't be even with the bottom edge.If they are take a file and carefully file down the stops so they sit about 1/32" below the cover edge. Clean as described above and then your leaks should be history

.

#8 11-08-2003, 02:02 PM

I believe the cylinder head bolts are "Streach-bolts", tightening it too much could cause it to break off. All it does is hold the head to the block, nothing else. There are no fluids going in/around it to leak. Make sure the valve cover is completely in its groove before you tighten anything

psfred · #9 11-08-2003, 02:05 PM

There are two tricks for getting the cover gasket to seat:

1). you must clean both the valve cover edge and the seating surface on the head with solvent. Carb cleaner, laquer thinner, paint thinner, gasoline, whatever. Must be absolutely clean and dry. No oil, no sealant, nothing. I'd not buff with steel wool, either, for fear of making the surface rougher than the gasket will seal.

2). Installation: place clean dry gasket on valve cover. No sealant, no oil (especially no oil), no dirt in gasket, must be clean and dry. Clean the groove on the gasket if necessary to remove ALL grit, oil, or dirt. Fit cover to head, making sure the gasket stays on and isn't twisted anywhere. Lift cover an inch or so and thump square on the head firmly. Repeat lifting and thumping until the muffled "thumph" becomes a sharp, distinct "clop". This seats the gasket properly on the cover.

3). Tighten until the "feet" touch the head. No need to really reef down on the bolts, 15-25 Nm is quite sufficient. Use only the head of the ratchet, not the end of the handle, to tighten and you will be just about right.

This applies to all MB valve cover gaskets. Installed this way they don't leak.

Peter

tnarg · #10 11-08-2003, 02:21 PM

Just posting to say I agree with the remedy posted by Kyle about filing the 'ears' of the valve cover, but be sure not to over tighten during reinstall....

PS I am new to this site. Thanks for having me.

russb · #11 11-08-2003, 07:59 PM

3 valver cover studs are the same length, the 4th one is different.
The odd one (can't rembeber longer or shorter) goes on the left rear for the bracket.
Found this out when I did a valve job on my 85 300D.

lietuviai · #12 11-08-2003, 08:22 PM

Just clean off all of the surfaces and use the brown colored Permatex sealer that stays tacky on the valve cover gasket. I have reused my old gasket with this sealer a number of times without any leaks. I don't know the exact type of Permatex sealer this is since it is in my garage and plus there is lots of the stuff all over the bottle that it came it so nothing but the name is still readable. It comes in a bottle with a brush in the cap. I have used it for many years with 100% success so far.

Kyle Blackmore · #13 11-08-2003, 09:26 PM

Peter- I missed the part about clomping the cover down, but cleanliness is the real secret here

BIGRED · #14 11-08-2003, 10:18 PM

I suggest you see if the tightening of the valve cover nut is really doing anything. In my case I found that the underside of the casting where the bolt goes through, was making contact with the head, thereby not allowing the gasket to sqooooooosh to the point of a seal.

I cut about 1/4" to 3/8" off the underside of the each casting point where the bolt goes through and now it seals really nice.

Don