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luckys420 10-04-2003 04:17 PM

Bypassing heater servo vacuum black box thing
1980 300 td
anyone know what coolent hoses to connect together in order to by pass my cracked vacuum servo thing( the black box with a bunch of vacuum lines) I would like to connect the hoses in order to get hot water to the heater core. there are four coolant hoses. I assume i would connect the one directly across from the auxillary water pump, is this true? or is there some kriss cross action going on from the four hoses?
thank you

Ridge 10-04-2003 05:06 PM

Heater problems

Just performed one of these junkectomies on a friend's car last weekend.

1. Only one of the hoses coming from under the thermostat housing is necessary.

2. That hose can be easily found by removing the air filter housing and the Chrysler thingie. Removed the "C" thingie by removing the three bolts from the right front wheel housing.

3. disconnect the electirc connector and remove the vaccum lines. Toss the unit.

4. The hose coming out of the thermostat housing splits in two. Remove the dividing connector. Toss the small hose and tubing.

5. At the tube where the dividing connector clamped up before, cut off with a hack saw about 1 1/2 inch of the tubing. Save this tubing.

Obtain some 3/4 inche hose and use the piece of cut tubing as a connector to the original outlet under the thermostat. Connect the other end of the 3/4 inch hose to the tube you just cut off. Make certain that there is enough 3/4 hose to mnake a nice uncrimped bend.

6. Now your thermostat water is routed up to the top rear of the engine.

7. Now you need a hose going from the engine beside the oil cooler into the firewall immediately near that engine out let.

8. The hose you just rerouted from the thermostat goes into the other hos projecting from the firewall.

9. now you have neated water all the time to the heater and by turning on the fan, you have heat.

10. has a heater vavle and a bowden cable so that you can install this and turn the hot water to the heater core off.

hope I haven't missed anything as my MBXs don't have that unfortunate hookup.

BTW, forget about the aux electric water pump. Sell it to someone who needs one.


luckys420 10-04-2003 06:53 PM

thanks ben! thats awsome
excellent directions, i will do this next weekend. Did you have to drain the coolant?

GottaDiesel 10-04-2003 10:21 PM

Can I ask a stupid question?

Why not just replace the broken part that you're "tossing" and have it all work like it should?

I'm just a newbie wonderin'


luckys420 10-04-2003 10:27 PM

No question is a stupid question. I have seen the part in question priced at $500 to $800, now you will probably understand. that is almost half as much as i paid for the car! once a car comes to the pick and pull I am there!

Ridge 10-04-2003 11:32 PM


glad you liked the info. A local stopped by today to thank me for telling him how to adjust the steering on his 380SL and told me his control unit cost him $1500.00.

Yes, you have to drain the fluid but by placing a bucket just right you can catch most of it.


psfred 10-05-2003 12:49 PM

Easier (although more expensive) solution:

Buy an aluminum body servo from Performance Analysis in Oakridge TN (no affiliation except being a customer) and a new amplifier. Should last forever, but it will cost. However, you WILL have a climate control again rather than full heat all the time.....


luckys420 10-09-2003 02:00 PM

where did you get this part? do you have contact info?

psfred 10-09-2003 08:48 PM

Performance Analysis, 1345 Oak Ridge Turnpike, Suite 258, Oak Ridge, TN 27830 rel (865) 482-9175 has the aluminum body.

Don't recall the price ($395 comes to mind), but has a one year replacement warrenty with a lifetime $95 rebuild warrenty.

No affiliate except I bought some door lock diaphrams from them.


luckys420 10-12-2003 10:18 PM

just did the by pass to day, alterd your metod alittle ridge, I connected the hoses together that go into the vaccuum box. in other word the two hoses on th right side, facing back of car, were hooked up togethe and the two hoses on the left side were hooked together. in the proces i took out the electric pump, i think it will go back in because i only get heat with some RPMs.
thanks all it was pretty cold this morning. nice to have heat.

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