Dealer Captive
 

HELP I have a 94 S350 thats running hot, the car is a Starmark that I bought it has 69000 miles and is flawless.
Took to dealer for running hot and upper radiator collapsing when cold dealer "supposedly pressure tested system" and said cap was bad I had checked cap before going and it tested fine. when I went to pick up car hose was collapsed with new cap they installed. Now there scratching there heads and they want to replace hose and there not sure it that either. when cap is released hose fills out. What could be wrong. they claim its not the head.
Funny the things there fixing are not covered under Starmark.

Need HELP

Possibly a coolant leak that seals up when it cools down? Metal expands when heated and crack opens up, then contracts when cools, seals the leak, and collapses the hose under vacuum? I'd bet its running hot because the leak is venting the pressure when hot. Head cracked?

Weak hose
 

The hose could be deteriorating. It should hold its shape when cold despite the depression in the cooling system. A new hose may be all that is needed.

The radiator cap was the most likley problem . When the cooling system is hot it will vent excess coolant through the cap into the overflow bottle and when the system cools down it draws the coolant back into the system from the overflow bottle. Its possible that there is a blockage in the hose from the expansion tank to the overflow bottle. If the system is not venting properly even a new hose will collapse.

I'm thinking head gasket. I guess the question is whether the running hot is a symptom of the collapsing hose (or the other way 'round) or whether both are symptoms of some yet unfound malady. Have you ever completely overheated the engine?

Earlier this year I went through a string of bad expansion tank caps. The 4th one finally worked. Went through the same deal you did - hose kept collapsing.

Not saying this is your problem - just saying that you'd be surprised how often various parts go through production problems.

Update
The dealer now states they contacted Mercedes Factory Rep and he said "Normal Hose collapse due to fluid contraction when cold"
"If head gasket failed the hose would expand" and that a temp of 100 celsius is normal.
My question is how does fluid "contract"
and how many of you have cars that run at a 100?
Engine is clattering and milage has been droping steady.
the say to change to Hess Fuel as that theres nothing wrong with engine.

I have this in writing from dealer.

New cap installed by dealer same problem hose collapses when car cools down

Something else to consider:

bad hose - cap still bad - bad expansion tank - t-stat issue.

http://db.mercedes.cx/mbsearch?words=collapsed+upper+hose&method=and&format=short&sort=score&config=fuzzy&restrict=mercede s&exclude=