Could a brake booster vacuum leak cause an overheat?

[john skene]

I just read this thread and its not the brake booster vacuum line leak causing the overheating, as near on maximum vacuum is at idle, which would cause maximum lean mixture and overheating at idle if the engine would actually run under those conditions. A lean mixture under normal running sounds more likely to be a problem, but is it possible that the rich start up injector is leaking, meaning the main fuel injection is set slightly lean to compensate?

[michaeld]

My advice, and I meant it in all seriousness - get your car to a qualified, certified, licenced machanic without delay.

It is a danger to you and the rest of the driving public you meet.

I appreciate your concern, Brian.

Actually, I looked into this diligently when I first got the car and noticed the booster issue.  I went to a couple brake shops, and, yes, they wanted me to let them work on my car without delay.  But when I questioned them further, they told me that the booster did nothing but "boost," and that the safety of the brakes was not affected.  I'm sure the car WOULD be unsafe for a 100 lb girl, but I assure you I have no problem braking.

I have obtained a master cylinder, and am in the hunt for a booster.  Given my long-suffered overheating problem, I have been loathe to put money into the car given the possibility that I had a fatal (by which I mean for the car) issue. 

I will actually be examining John's suggestion (which is similar, albeit more detailed) to a few others.  It sounds like there's a good chance I have an injection issue of some kind, and would like to get to the bottom of it.

[Brian Crump]

Good luck then,  and may the angels be with you. 
Regards,
BC

[michaeld]

Thank you, Brian.

They WERE with me today: I passed my smog test (the enhanced version, nonetheless!) with flying colors.  My angels not only stop my car for me, they chase away hydrocarbon, carbon monoxide, and nitrogen oxide molecules away as well!

I think my angels deserve a great deal of credit: I keep them busy, and I'm sure they often wonder whether I'm worth all the bother I cause them!

[Brian Crump]

Good angels are good; bad ones can be a pain in the butt...
Have you TESTED your thermostat?
Regards,
BC

[michaeld]

My angels have to be SAINTS to put up with my shennanigans.

I replaced the thermostat.  But yeah, I tested the old one after taking it out of the car, and then tested the new one before installing it to have a better benchmark of comparison for how the things were supposed to work.

I can also say w/ certainty that the current thermo works fine, as I have too many times added coolant (and waited for the thermostat to open).

Regarding thermostats, I put a 175F unit in (What HAD been in the car previous).  The smog guy suggested I install a HIGHER TEMP unit, claiming that it would reduce my overall temp.  I would have thought it to be the other way around.

Obviously a bad thermo would cause me to overheat; but I can't believe I'd solve my problems (bad as they are) merely by installing a higher opening temp thermostat, given that the 175F unit apps to the car.  So I won't mess with installing a hotter unit until I fix what's really wrong.

[torana68]

following on from the discussion elsewhere I posted your exhaust results to another group and received one reply suggesting it was lean and this reply:
--------------------------------------------------------------------------------

there is a mixture adjuster in top of the fuel distribution block you can see the hole for it on top of aircleaner, they go out at the drop of a hat i would richen it up a bit, do it with air cleaner on. have you checked the thermostat they bugger up all the time as they are a bypass type thermostat. they usually crack on top brace of the locater falls out. be careful pulling them out as the housing is a prick to get off.


it is suggested you need a 4 gas analyser to do this properly, not something you can do by the seat of your pants, might be worth a look
Roger

[michaeld]

Roger,

Thanks for asking about that and posting back.

I posted my "smog test" results on mercedesshop.com, and one of the guys that I've always highly regarded told me I was DEFINITELY running too lean (the 0.00 %CO tipped him off).

Before I do ANYTHING else, I will have that examined.

I note that you mentioned the need to have a gas analyzer to do this job.  So I suppose it doesn't matter overly much that I wasn't able to find the mixture adjuster on the air cleaner (of course, the Haynes manual gives you an extreme close-up of the idle mixture screw to insure that you have no way to look for it!).

I'll probably have to wait awhile before taking the car down to get that job done.  But I'll be sure to post whether adjusting the fuel mixture does the trick.

[Papalangi]

Michael,
The mixture adjusting screw is hidden under a socket head cap screw.  Socket head cap screw means a screw that an allen wrench fits and has a head that sits on the surface it's tightened against.

Imagine a center line, front to back.  On this line, between the round raised area the air cleaner fits on and the cast iron part of the fuel distributor lies the mixture screw.  It cannot be reached with the air cleaner on.  Remove the socket head cap screw and using a 3 mm allen wrench, turn the mixture screw.

See http://handbook.w116.org/Engine/107/M117_45/073-100.pdf for pictures.

Michael

[500eguy]

on a side note, i replaced my brake booster on my car. I bought it for about $160 at Car Quest. It was a refurbished item but works very well!

[michaeld]

on a side note, i replaced my brake booster on my car. I bought it for about $160 at Car Quest. It was a refurbished item but works very well!

You've always got to have that guy that posts something that has absolutely nothing whatsoever to do with the topic, don't you?  I mean, what does a thread with "brake booster vacuum leak" in the title possibly have to do with actually replacing the brake booster?



I'm glad you mentioned that, 500eguy.  I took a quick look at brake boosters, and when I saw they were priced at about $600 USD, I began to contemplate alternatives.  I wanted to find out how the refurbished units (which I found as low as $137 US with core exchange) worked.

Did you find it easier to pull out the driver's seat in order to have better access to the necessary under-dash contortions?  Were there any tricks that you discovered?  I'll probably tackle mine this summer.

Thanks for posting that location, Papalangi.  At this point, I'm planning to have someone do the job for me (as per the wisdom of torana).  But I did consider giving the CO mix screw a 1/4 turn in the rich direction just to see if it has any positive impact.  It'll take me a couple of weeks anyway to get the car down to the folks who would do the job for me (you know, that whole, bring the car down, and then either have a ride home, or start walking thing...).

[500eguy]

aha a leak:) well it was not to hard to install the booster, although i did have some help from a more "experienced" benz friend. I had a leak in my booster, i actually had no pedal boost at all. I did the same thing with the core exchange.