Hello All,

I am experiencing the following problems with my '84 300DT and I'd like to know what you think:

1. I figured I was having a vacuum problem when I noticed the car shifting rather hard. After making sure that the automatic transmission fluid was at the proper level (by changing it) and ensuring that all the vacuum lines were tight, and replacing both 3-way vacuum valves (which were brittle to the point of dissolving) and other miscellaneous vacuum hoses and fittings, etc. the shifting did get better, but it's not completely fixed and still "clunks" as it shifts. Somedays it works perfectly but I've forgotten the last time "Someday" was. It also tends to shift from 1st to 2nd after revving up to 4500 RPM which doesn't feel right to me.

I'm thinking that the one piece I haven't replaced yet may be the culprit: the Vacuum Valve itself. What do you think?

2. I just noticed the second problem now that the weather has cooled down a bit ... the heater which normally will burn you out of the car is quite cool when the car is moving (i.e., 40+ MPH). As the car slows down (and stops), the heater warms up to expected levels. I experience almost the same thing with the A/C ... it's cool but not cold at cruising, but chills down appropriately when the car has stopped.

I'm thinking that the problem here may be the Mono valve. These are, of course, not inexpensive items, though, I did notice that ************************ does have what they call a Mono Valve Repair Kit (the plunger chamber and seal) for a mere $29.

3. And finally, as an aside, is there any quick idea as to how the drivers side window regulator can be removed? I'm guessing that the window must be in the down position before the regulator and motor can be removed?

Any suggestions would be greatly appreciated,

Thank you!

__________________
Peter Lehmann
'84 300DT 279K
'99 E300 92K

As to your heater problem, I had the same exact symptoms with my heater. After reading a few posts about the monovalve, I removed the valve component and found a cut diaphragm. I bought the monovalve repair kit (that component), put the part together, and my heater works as good as new. Remember to remove the four screws on top to get the the valve component. Good luck.

Window regulator: "Both" is the answer to window position: With window part way down, remove the clip, washer and plastic (what I call rail runner) from the horizontal channel that actually holds the glass which will get the lift arm unhooked from the horizontal channel. Then manually move the glass up to the closed position, otherwise the glass and horizontal channel will block getting the motor and lift arm out the bottom half of the door. After removing the nuts that hold assembly to the door (and two screws for the wires), you should be able to work the regulator assembly out---not easy the first time.

__________________
K. Weimer
300SD (1)
300D (5) [Plus 1 parts]
300SEL 4.5 (2)
280SE (4)
280 (2)
250 (1)
250SE (1)
240D (7) [Plus 1 parts]
220D (11) [Plus 3 parts]
200D (2) [Plus 1 parts]
180c (with sunroof)

1995 Nissan UD1800 rollback
"If I can't fix it, it don't get fixed"

Thank you kweimer and kearls66!

kearls66: The Monovalve repair kit worked. I, too, had a small tear in the diaphragm of the original monovalve. It's amazing what a little tear will do.

kweimer: Your regulator directions put me on the right track. Thanks for your help!

And just in case anyone else is interested ... I've attached a small .jpg of the regulator assembly and some quick visual hints.

Attached Thumbnails

 

__________________
Peter Lehmann
'84 300DT 279K
'99 E300 92K

Wow pglehmann, thats a life saver there.


Does that picture hold somewhat true to the rear doors?

__________________
2005 Audi A4 1.8T CVT -Silver/Black "Siegfried"

1982 300D - Silver/Blue "Ralph" -For Sale:
http://www.peachparts.com/shopforum/showthread.php?p=852260

1989 VW Diesel Jetta Blue/Blue "Bodo" RIP

That is a GREAT picture for all of us DIYers!

What package did you use to edit the picture?

__________________
Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)

Capt Kirk: I, too, find pictures much more useful (and faster) than words. The rear regulators should be quite similar ... but if you're patient, I'll be replacing the rear driver's side regulator in the next several days and I'll take a picture and post that as well.

mplafleur: Believe it or not, but I added the text using powerpoint and then saved the file as a .jpg file. I was surprised how well it worked.

__________________
Peter Lehmann
'84 300DT 279K
'99 E300 92K

Here's a picture of the rear regulator assembly as I promised quite a while ago.

Attached Thumbnails

 

__________________
Peter Lehmann
'84 300DT 279K
'99 E300 92K

This shows how to repair the power window mechanism, I assume. I hope to repair the locks, which I hope is simpler.

Your vacuum leak is probably one of the diaphrams under the dash. It's very seldom a valve, they only open or close. If one of the diaphrams have dry rotted, it will leak. Some of them are a booger to get to. I've had this problem and the first one I'd replace is the one for the center flaps. It's to the left of the glove box (at least on my 85 300SD).

Monovalve: when they stop they will always stop open allowing heated water in all the time. It should get hotter w/ faster RPMs.

What does your engine temp get to? It could be a stuck thermostat. It may not be closing enough to keep the coolant heated. It's cooling off too much with air flow but heats up sitting still.

As far as your A/C: Never heard of this problem. Usually the slower the RPMs the less cool the air. Unless it is a problem with the Climate Control Unit not opening the correct flaps properly?

The aux water pump: If it fails you will have less heat at idle. It increases coolant flow at low RPMs. HOWEVER, when they build up enough resistance in the motor it WILL burn out your Climate Control Unit. It can be repaired with a wire soildered in the right place.

Captain,
I think that actually the coolant gets cooler with higher RPMs and speed because the coolant is circulating faster and passing through the radiator more thus releasing more heat. As always, I could be wrong.

Alex

__________________
1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside

Dieselhead,

I think we're talking about two different things. If the thermostat is working properly, it is only allowing enough coolant to go through the radiator to maintain a proper engine temp.

If the Aux water pump is dead, at low RPMs the coolant flow will be very low. The coolant doesn't flow directly through the heater, the monovalve opens and closes for this. Low coolant flow to the heater means less hot heat. High RPMs increase this flow and heat gets hotter. (Can I say that?)

Two things here; monovalve and aux pump. Monovalve dead, always open, always heated coolant to heater core. Aux pump dead, no assisted flow to heater core, (plus pump actually will restrict flow when not turning), less heatedd coolant to core at low RPMs but better at high RPMs.

TEST: Unplug the monovalve to diable and see if anything changes.

Also, touch the aux pump or listen for it to see if it's working.

Listen for vacuum leaks under dash, check line going to dash from engine compartment with vacuum guage. It should hold vacuum good, if it leaks suspect diaphrams.

Check flap control. Is heat coming out at center and defrost as it is supposed to? What about lower at feet?

Captaincrunch,

You may be correct in theory, but upon doing a search here for no heat, both of those two situations come up.

1. Aux. water pump failing typically means no/low heat at idle, and good heat going fast.
2. Monovalve bad, typically means good heat at idle, no/low heat going faster down the road.

My wagon was experiencing the latter and I changed out the plunger (monovalve repair kit) last thursday night. She throws more heat out now than a cherry red wood stove.

It worked for me.

I guess I stand corrected.

As long a things get fixed and everybody stays warm!

I took the long way around to find I needed a new diaphram (as in: "I've got an extra aux pump, now").