On a couple of occasions after working on the 300E, I started the car and saw white smoke coming out the tailpipe. Admitedly this was at night in high humidity, but the last time, I put my hand in the exhaust, and it smelled sweet.

I ran a compression test, and got this:

182.50
167.50
175.00
167.50
180.00
182.00

I may be relocating before year end, so I decided to replace the headgasket while I have the facilities to do it myself.
Since concensus seems to be get a valve job while the head is off, I called the dealer and asked which machine shop they use.

In talking to the machine shop he said he only replaced the valve guides "if they are worn out" .

From reading M103 valve guide posts here, it sounds like I should insist he replace all the guides.

Do I go with his opinion, or insist on all new guides?

why not do it at the same time? The extra cost should be minimal and, once you have the head out, you should be able to see the condition of the head and give you better idea. The machine shop in my area quote me around $300-350 average for a head job. Depending on its condition of course...

__________________
J.H.
'86 300E

This guy asked $220, which is bargain enough that I do not mind paying extra to get all the guides replaced. Question is, do I go with his judgement on only replacing the worn guides, or insist on replacing all of them?

If they are the original '88 guides, be advised that the material used has been upgraded 3-4 times since your car was built. Also, M103s are tough on guides given the way the valves are actuated - I understand there are a few aggressive angles in there that can be tough on the guides.

If I were you (and I was in the same situation last yr. with my '88 300TE) I would do the guides now, and forget about them for the next 150-200k miles.

__________________
"If God had meant for us to walk, why did he give us feet that fit car pedals?" Sir Sterling Moss

Michael
2014 E63S Estate
2006 SLK55
1995 E500
1986 Porsche 944 turbo

As stated the 103 valve guides tend to wear, so as long as the head is off at your mileage I would recommend a complete refresh which would include all new valve guides. Also, the valve stems should be measured for wear,and if it is more than half a thou, they should be replaced. Chances are the exhaust valves may need to be replaced.

Reseat the valves and assemble the head with new stem seals and you should be good for at least another 100K miles.

To change the guides the head is heated up to about 400F in an over, then the old guides are tapped out and the new ones tapped it - just takes a couple of minutes. It takes a lot longer to actually measure the valve guide IDs using an inside caliper and a micrometer, but most mechanics use a "wiggle test" - with the valve installed and slightly off the seat you wiggle the end of the stem. An experienced guy knows whats good and what's worn.

Duke

It is common knowledge that valve guide wear has always been a problem on M103 engines. I believe the "aggressive angle" is also referred to as valve stem/quide side force [ cam-valve swipe].

I agree with the others in that it would be foolish to not replace the valve guides and seals since you are going to the trouble of removing the head. Valve seals can be replaced without removing the head, but not valve guides.

__________________
Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

Valve guides in the 103 motor were upgraded in April of 1988.

Steve Brotherton's second post in the following thread says it all.

cost of valve stem seals vs. do-it-yourself on '89 300E?

From the plate on the door, the car was built Nov 87.
While I agree with Steve's sentiment, this is bit of an oddball situation. I am doing something which is not immediately critical because it is convienient now, and likely will not be when it becomes necessary.

Thanks to you guys for the reinforcement; I really wanted all the guides replaced, but did not want to appear so presumptious as to tell someone who looked at these things every day how to do business.

It seems if this is enough of an issue to reengineer in the middle of a production run, it may as well be updated while it is easily accessed.
Perhaps since the car is an 88, he assumed it already had the updated guides.