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VWBusMan1
Date registered: Dec 1899
Location:
Vehicle(s):
| Vacuum/ heat system simplification on a '78 300CD, any ideas?
Vacuum / heat system simplification on a '78 300CD, any ideas?
Call me a simpleton yet I find the vacuum system on my '78 to be way too complicated--especially because I don't mind locking and unlocking things with keys and I'd be happy if my A/C and heat were just On/Off or blew through the defroster.
Have found a couple of threads that touched on this yet nothing, so far, that talks about:
1 Simplifying the heat and convert to one vacuum servo that turned the heat on or off. With that, I'd be happy to have all air, hot or cold, come through the defroster.
2 Getting rid of the electric hot water pump and just go direct assuming the heat will work somewhat without it. Hey, my part of the planet seems to be warming very quickly.
3 Plugging what I'm sure leaks throughout the system and just opening and closing my door and trunk with a key. I can get a locking diesel cap somewhere I am sure.
4 And, if all this vacuum is eliminated, does the diesel produce enough vacuum to actuate the power brakes without the vacuum pump?
I don't want to do anything that would damage the vehicle yet for me a simple daily driver is all I need and the more work I can do on it myself the longer I'll be able to keep her.
Any feedback and/or direction will be greatly appreciated, thanks much, Mark |
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Inkblotz
Expert
Date registered: Apr 2006
Location: Georgia
Vehicle(s): 90 300GD "Thundering Turtle II", w/ 603A turbo
Posts: 3186
| RE: Vacuum/ heat system simplification on a '78 300CD, any ideas?
You can disconnect and plug the the vacuum for the doors, trunk and gas cap cover. To do this you will need to remove each door panel and remove each vacuum unit, otherwise it would be very tough to pull up on the door locks. This is true also for the the locking gas cap cover which is hidden by the rear plastic panel. The drivers door has the master vacuum valve while everything else has mini diaphram units.
In the engine compartment next to the brake booster you will find a nest of colored vacuum lines. There is a line that goes to the locks, the AC/Heater, you will see one vacuum line that goes to the FI pump. The task if you are up to it is find the vacuum line that goes to the locks and plug it. You can must do this after you have removed all your door vacuum units (first paragraph). Leave the AC/Heat alone as it is all vacuum based and would designing a new system for it to function properly.
Regarding the Diesel vacuum pump it is essential as it is tied into the start up and shut down of the engine. Replace old cracked rubber connector lines with new ones and it will run forever.
The main vacuum failure in these cars came from the door locks. The diaphrams would tear or crack thus vacuum would be lost throughout the entire system. Tracking down these leaks in the system are a real headache. You can hunt down the problem with a vacuum tested and by lifting up the carpet find the rubber and go door by door looking for a weak vacuum. when you find it you can remove that door panel and replace the diaphram.
Anyway I am rambling on a bit hope this can get you where you want to be.
Mark
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ForcedInduction
Regular
Date registered: Sep 2006
Location: Federal Heights, CO
Vehicle(s): 1980 240D 3.0VNT
Posts: 89
| RE: Vacuum/ heat system simplification on a '78 300CD, any ideas?
VWBusMan1 - 1/30/2007 10:54 AM 2 Getting rid of the electric hot water pump and just go direct assuming the heat will work somewhat without it. My heater works very well without a pump. I don't know how well the flow would be through the monovalve, but my manual valves flow well enough to get over 140*f at the vents. |
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BenzDieselTuner
Date registered: Dec 1899
Location:
Vehicle(s):
| Re: Vacuum/ heat system simplification on a '78 300CD, any ideas?
is your heater pump not working or something? |
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Inkblotz
Expert
Date registered: Apr 2006
Location: Georgia
Vehicle(s): 90 300GD "Thundering Turtle II", w/ 603A turbo
Posts: 3186
| RE: Vacuum/ heat system simplification on a '78 300CD, any ideas?
The primary purpose of the electric water pump on the front left side of the engine is to provide additional hot water flow when the car is not moving. During this time the water pump is moving slower so the MB engineers wanted to keep their diesel cabins warm by adding the electric pump.
Mark |
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