Valve Stem Seals on '95 S350 - 603.971 - PeachParts Mercedes-Benz Forum

oldsouth · #1 04-28-2004, 02:22 PM

What tools will I need to replace the valve stem seals on this engine without removing the head. I have never been into it at all. I am getting some blowby and at over 250,000 miles feel it is time to do this job. I wasn't for sure if a valve spring compressor is all I will need.

md21722 · #2 04-28-2004, 04:05 PM

Problem is that these cars don't have rocker arms so standard valve spring compressor tools won't work. The dealer tools are about $500. Valve stem seals aren't said to be much of a problem on diesels because there is no vacuum. Blowby is usually caused by problems with carbon build up on rings, etc.

My '87 300DT with the 3.0L version of your engine doesn't have much blowby, and my '87 190DT with 379Kmi didn't have much either. To measure blowby, I removed the breather tube from the intake and blocked it with my finger. After one minute at idle there was no noticable blowby. Now, my hard staritng '86 190D 2.5 will make enough blowby in 5-6 to cut off the motor. My project car 190DT will do the same in about 26 seconds.

How have you measured blowby?

Regards,

gsxr · #3 04-28-2004, 05:36 PM

I've done this job and it's not fun. You will need the proper tools - either the quality factory items that work on a lot of different engines ($500+), or the Sir Tools junk that only works on a few engines including the 603 ($225). If you're not getting blue smoke out the exhaust after extended idling, and don't have unusual oil consumption, I suspect the seals might be OK (although it's not a bad idea to replace them regardless). You absolutely want to use the OE dealer "genuine Mercedes" valve stem seal kit - NOT the aftermarket kit!!

oldsouth · #4 04-28-2004, 09:23 PM

Great information gsxr! I am not getting any blue smoke, only blowby out of the pipe coming out of the valve cover. Oil comsumption has gone up from 2 quarts in 3500 miles to 2 quarts in 2500 miles. Car is idleing rough and I think it is the injectors but other than idle it runs great. I need to get back with the dealer but the mechanic said he don't think they have the tools to do the job and would probably take the head off and send it to a head shop. I don't like paying Mercedes prices for someone else to do the work. I know a good Mercedes mechanic than I can get to work on the car at my home if I can keep him off of crack long enough. He don't have any special tools though. I am not for sure if I even need valve seals. I am definately replacing the injectors though and will do a compression test. Wouldn't a leakdown test tell me about the valve seals? Exactly how does one do a leakdown test? After compression, see how long it takes to leak the pressure off? I see nothing in my Alldata service manual about leakdown tests.

md21722 · #5 04-28-2004, 09:27 PM

One of the problems with not using the correct tools is that if the incorrect tool slips, it can damage the lifter bore and then you're really screwed. Even using the valve bridge tool, if you dont' have the correct diesel tool it can happen. This information is the advise of an experienced MB mechanic.

I would strongly suggest "ignoring" the valve stem seals unless you have the resources to do the job correctly.

Increased oil consumption in a 350 might be destruction of the block/bending of rods? I realize you've made it a long way already and it may not be the problem. Also possibly increased oil consumption from the turbo ?

Regards,

gsxr · #6 04-28-2004, 09:35 PM

Leakdown tests check the condition of the valve seats and piston rings. Nothing checks valve seals except the presence/absence of blue smoke.

A compression test can be of some use as well. The leakdown test requires high pressure air (from a compressor) and a special tool with adapter, to pressurize the cylinder. The tool has one or two gauges and tells you the percentage leakage from the cylinder. You can figure out what's leaking be seeing where the air is going - crankcase (rings), or intake/exhaust (valve seats).

Your oil consumption is excessive for a 603, though. Mine are one quart per 5-8kmi and most other people are in the same range. With yours at one quart per 1250 miles, I have a really really bad feeling you're about to embark on the dreaded bent-rod issue that plagues all 603.97x engines.

That is the most probable cause of the oil loss (it COULD be the turbo but that's not really likely.)

A member of the MBZ email lists recently ordered a factory 603.97x crate engine from Mercedes, he's expecting it to arrive from Germany shortly. After much research into repair shops, machine shops, etc he finally concluded that truly was the most economical way to fix the problem (parts & shop labor are NOT cheap!). If you end up having to go that route, I can put you in touch with him for some pointers. In the meantime:

http://www.meimann.com/docs/mercedes/OM603_rebuilt_engines.pdf

oldsouth · #7 04-28-2004, 09:36 PM

Just had the turbo re-built about 20,000 miles ago. A compression and leakdown test should tell me about the health of the internals shouldn't it?

gsxr · #8 04-28-2004, 09:38 PM

Quote:

Originally posted by oldsouth
Just had the turbo re-built about 20,000 miles ago. A compression and leakdown test should tell me about the health of the internals shouldn't it?

It will help. If the numbers are BAD, then you'll know you need major work. If the numbers are OK (or within min spec), it doesn't necessarily mean things are OK... just that they're not bad enough to register as anything besides increased oil consumption (for now). As the condition worsens, though, compression will get worse, smoking will increase, and power will drop....

oldsouth · #9 04-28-2004, 09:44 PM

I have already checked on a crate engine and it is no longer available according to the local Mercedes dealer and also Phil at Partshop. You can buy a non-Mercedes rebuilt complete engine or just the block from Mercedes. What's the best way to check for the dreaded bent rod? Look in the top of the cylinder for egg shape would be one way but the head has to come off for that doesn't it?

gsxr · #10 04-28-2004, 09:51 PM

Quote:

Originally posted by oldsouth
I have already checked on a crate engine and it is no longer available according to the local Mercedes dealer and also Phil at Partshop. You can buy a non-Mercedes rebuilt complete engine or just the block from Mercedes. What's the best way to check for the dreaded bent rod? Look in the top of the cylinder for egg shape would be one way but the head has to come off for that doesn't it?

From a message dated 4/24/04:
> I thought I'd share this information with you. I just ordered a 603.970
> engine from Mercedes. They had me on their waiting list since they didn't have
> any engines available in Stuttgart. Now they do. They will air freight it next
> week from Germany.

Sounds to me like you can get them now. (??)

To check for the bent rod, I'd probably start with a compression test (HOT) because you can do that with the engine intact.

After that, you need to yank the head off and measure the piston protrusion at TDC for each piston, and also measure the cylinder bores for eccentricity. I'm not sure if you must remove the pistons to do this. If any cylinder is ovaled out, it's time for another motor, unfortunately...

oldsouth · #11 04-28-2004, 09:52 PM

The pdf link you listed, is it genuine Mercedes engines?

I have pondered this for a long time -- whether to fix the car or sell it if the engine ever went bad. I like the car a lot. I just bought a 98 E300D for my son and although it is faster, it just ain't an S-Class. I think I will be keeping the 350 for a long time. Bought it new and I know a good deal about it now. I can fix most problems that come up now after a lot of prior trial and error.

oldsouth · #12 04-28-2004, 09:54 PM

Personal question ---- Would you go to the trouble of removing the head or just run it until it stopped?

gsxr · #13 04-28-2004, 10:04 PM

The PDF has prices for genuine Mercedes engines from MBNA through your local dealer, Rusty, Phil, etc. The prices are several months old though and could be higher now. And the dealers need to check stock in Germany to see if they are indeed available! I agree with you - the W140 is a fantastic car, and if you've owned it since new and would like to keep it another 5-10 years, it's worth fixing/replacing the engine.

As to what I would do? Hmmmm. Good question. I think I would attempt a compression test now, just for grins. Then keep driving the car until symptoms get significantly worse - which could be a LONG time. At that point (low power, bad smoking, etc), I'd do another compression test just for grins (and to see the difference from the original test), and just replace it with a crate motor (assuming one is available). If a long block can't be sourced at a reasonable price, a factory short block would be the next choice, re-using your existing head (with a freshen-up valve job, seals, etc). Last choice (IMO) would be an aftermarket rebuild from Metric Motors - not because they don't do good work (they do), but because the last time I checked, they're actually more expensive than the MB crate motors!

oldsouth · #14 04-28-2004, 10:19 PM

One other question. Is the Mercedes crate engines new or rebuilt? I would think rebuilt at that price.

gsxr · #15 04-28-2004, 10:37 PM

Part numbers with a suffix, usually -88, are rebuilt. (A suffix of -70 is the refundable core charge.) If there is no suffix, just a standard 10-digit number (xxx-xxx-xx-xx), that indicates new - not rebuilt.

It looks to me like you can get a rebuilt long block (with head) for $6k, or a NEW short block (no head) for the same $6k, or get a complete NEW engine with injection pump, turbo, water pump, manifolds, AC compressor, serp belt, on a sesame seed bun for $20k. (ouch!!) I would go for the rebuilt long block if at all possible (block + head only, no IP, no turbo, etc etc)