Could my hot vacuum leak be bad valve guide seals? - PeachParts Mercedes-Benz Forum

nhdoc · #1 08-23-2007, 02:04 PM

I've been chasing what I thought was a vacuum leak on my '64 220Sb to no avail, but now I have a theory that the valve guide seals may be leaking enough to cause the hot-idle problems I have. Is it possible for the seals to be so bad, especially when the engine is hot to cause the car to not idle but stall to do air leaking past the seals? I get lots of smoke when it does restart (with full pedal) but unless I crank up the idle mixture by 1.5-2 turns it will not idle, just dies at idle. If I leave the mixture rich and restart cold it revs like crazy. Would leaky seals cause bad vacuum leaks and get worse when the engine gets fully hot??? I only have like 8-9" of vacuum when the engine is at idle.

Mike D · #2 08-23-2007, 02:14 PM

Extremely low vacuum can be an indication of late valve timing. Usually caused by chain wear.

I'm not saying this is the cause of your vacuum problem but it's something to consider.

I've never seen bad seals cause a vacuum problem but worn valve GUIDES can. Of course, I've never seen Paris either.

nhdoc · #3 08-23-2007, 02:33 PM

Quote:

Originally Posted by Mike D

Extremely low vacuum can be an indication of late valve timing. Usually caused by chain wear.

I'm not saying this is the cause of your vacuum problem but it's something to consider.

I've never seen bad seals cause a vacuum problem but worn valve GUIDES can. Of course, I've never seen Paris either.

I spoke with an older German tech today who also said it is probably the valve guides...we'd have to pull the head to replace them so it looks like that's the direction I am heading in. He's going to swing by next month and look it over. The valve timing is something I had not considered though...

todds · #4 08-25-2007, 10:22 AM

Hey Marty,

Do you have any recommendations on good shops for our old finnies here in the Boston area? I'd drive to NH for a good one who knows the cars inside and out.

nhdoc · #5 08-28-2007, 06:20 PM

Quote:

Originally Posted by todds

Hey Marty,

Do you have any recommendations on good shops for our old finnies here in the Boston area? I'd drive to NH for a good one who knows the cars inside and out.

I haven't run across anyone I'd trust to handle an old fintail, sorry, that's why I am always posting here

In fact I don't even know of a good shop for modern Benzes in the Boston area...I had such poor service from a highly recommended shop in the Norwood area I decided to just do my own work from then on.

Mike D · #6 08-28-2007, 06:44 PM

Have you ran the car with the valve cover removed? Try it and see if you can spot a valve guide moving up and down. I had a M115 with a worn guide which would only work loose as the engine got to operating temperature. Car ran fine cold but developed an annoying "clack" and stalled at a warm idle. It did give the car a really sweet "trumpeting" sound as it ran up the rpm scale.

nhdoc · #7 08-28-2007, 07:05 PM

Quote:

Originally Posted by Mike D

Have you ran the car with the valve cover removed? Try it and see if you can spot a valve guide moving up and down. I had a M115 with a worn guide which would only work loose as the engine got to operating temperature. Car ran fine cold but developed an annoying "clack" and stalled at a warm idle. It did give the car a really sweet "trumpeting" sound as it ran up the rpm scale.

Wouldn't that make an awful mess? Oil all over the place?

I am still not 100certain that my trouble is in the cylinder head, though it has been somewhat cooler lately the car has been running well. Tomorrow I plan to install a new 79C thermostat and take it for a test drive. A loose guide is an interesting thing to consider though, as it would explain why the problem is intermittent and sometimes the car seems to run fine, other times it is horrible and when cranked can hear a whine that sounds a little like a whistle.