Is it time for stem seals in my 300E???
 

Hello board,

Last night I was helping a stranded mororist who was having car trouble. Well I was helping that person for about an hour, I had my car on because I needed the light form my healights in order to see what i was doing. Well I finally fixed his car, but my car was at idle for over an hour(not a good idea), I noticed slight traces of blue smoke out the exhaust. By the time I went to pull off, my car was hesitating badly and left a huge cloud of blue smoke(burning oil). The car hesitated and idled rough for about 10 minutes and then returned to normal. My oil consumption is 1quart every 400 miles.

-When I start my car in the morning,there is no cloud of blue smoke.

-When I pull off from a light, there is a very slight cloud of smoke.

Could it be time for stem seals??

Will any of those "higher mileage" oils actually re-condition the seals in the m103 motor??

Has your car had any valve work done?

Early M103's had soft valve guides that wore rapidly, and if this is the case with your car, I'm not sure if new valve seals will help all that much. OTOH, replacing the seals is a heck of a lot easier and cheaper than a valve job, and if the seals have been in the car 16 years, they've probably lost a fair amount of the sealing capacity anyways.

FWIW - had valve seals done on the '87 and '91 when both were burning about a qt every 800 miles or so. That helped reduce oil consumption to about 1200 miles, then I switched to a higher weight oil (from Mobil1 10W30 to Delvac 1 and now going to M1 15W50) and now it's about every 2000 miles. Don't know exactly why, that's just the way it happened.

My engine has 104k on it. Would it be a good idea to replace the seals and guides? A valve job is very expensive!

If you plan on keeping the car a few more years new valve seals would be a good investment; 103 engine seal materials changed in mid-'88 (viton for BOTH inlet and exhaust). The original seals are likely hardened and cracked and cannot be "revived" with any motor oil or snake oil crankcase additive.

I think others have reported that the job costs around $300 at a commercial shop, which is not unreasonable. There are likely aftermarket seals available, but it's tough to know if they are as good as OE. I'd recommend insisting on the MB parts to make sure you get the best quality seals.

Excess oil consumption will eventually reduce the effectiveness of the catalytic converters, which could lead to failed emission tests and the need for new converters, and given their cost, a valve seal job is worth the insurance.

Duke

Yep. pull your plugs and you will see the rearmost 2 are heavily fouled.

You have 2 options- stem seals- about $400. BUT, some mechanics won't do it because they might not last long.

Valve Job- I paid 1800, but would attempt it myself if I had a second car to drive.

Until you get the car in, just replace those fouled plugs to keep the car from missing after idling. Its only going to get worse.

Mike

Will adding a heavier weight oil reduce the oil consumption?

I currently am using Castrol GTX 20w-50


What is the highest weight oil I can use in the 300E without doing damage to the motor?

I am in HOT HOT Miami,FL

Heavier oil will not slow down oil consumption. Been there.

If your seals are tired, any viscosity will seep through.

It's my opinion that seals can be tired and your plugs may not show it. Been there too.

Mike Murrell what do you advise?

Anyone else care to chip in?

My 1988 300ce began burning oil at a rate of a quart every 1,000 miles or so about a year ago and progressively got worse..down to about one every 400-500 miles. When I had the 52,500 service done 4/03, the MB service rep asked me if I was burning oil. Told yes, he said I probably needed valve seals.

Had the job done at 57,900 by an indy in July.. Parts: Seals = 31.00, valve cover gasket = 17.50. Labor (4.2 hrs) 361.20.
Had the 60,000 service done by MB two weeks ago. During that period, no noticeable oil consumption. Problem solved.

I guess this shows that seal deterioration and failure can be a function of age as well as use.

I didn't catch the mileage on your 87 300e, but if it's not too high, you may solve the problem with just doing the seals.

Good Luck.

Jim