82 300td. The heater works great.... as long as I don't drive over 50mph. Where should I look first?

Also... I think my vacuum pump is going out. Power brakes quit on me yesterday, and there's a loudish "ska ska ska ska ska ska ska" coming from the general vacuum pump area. It's a pretty easy rebuild/repair right??

Thanks for your help guys...
Chris

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'90 300SE --- 173k miles --- (Odometer just stopped working!)

'85 Cali 300D --- 193500 miles --- (Second one) Sold Nov '10

'82 300TDT --- 236,xxx miles --- (My first one) Sold July '09

I'd check the thermostat for the heater issue.

As for the vacuum pump, fix it before running the car any more. You can do serious engine damage otherwise.

I have the same problem with my heat. I was directed toward the monovalve (on the firewall next to the battery). I have not had a chance to investigate it but I'm told the internal diaphragm gets torn and causes the problem you described. I think you can replace it by opening the valve, but i'm not sure. You may have to replace the whole valve.
Hope that helps- I don't know about the vacuum problem.

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'83 300D Turrrbo 295K miles

Regarding the heat, start with the monovalve, it's the likely problem (do a search).

Regarding the vacuum pump noise, don't drive it with a bad vacuum pump, refer to my vacuum pump horror story:

http://www.peachparts.com/shopforum/showthread.php?t=151324

Well, here's something else to consider about the vac pump: The hydraulic fluid pump (for self leveling system) is directly about the vac pump, and my fluid was almost empty!! So i think that's my "ska ska" problem.

__________________
'90 300SE --- 173k miles --- (Odometer just stopped working!)

'85 Cali 300D --- 193500 miles --- (Second one) Sold Nov '10

'82 300TDT --- 236,xxx miles --- (My first one) Sold July '09