strange heater operation
strange heater operation
Writing from up here in Montana where it gets cold in winter and I need my heater to function properly. Got three of these TD's (one running, two for projects). Actually the heater does function properly at low rpm's around town but once I get out on the highway at higher RPM, the heat leaves the heater core. I have removed and checked the operation of the electric heater valve which is working perfectly. Tracing the movement of coolant, the only other possibility I can come up with is a faulty thermostat that does what it is supposed to at low RPM but causes coolant to not move through the heater core circuit at higher rpm's. The engine warms up nicely and operates at normal operating temperature. I make my own biodiesel for the car, have personnally rebuilt my IP, replaced head gasket etc and I have to admit, this has me stumped. This is just a weird problem that I havent been able to solve yet. Since the thermostat seems like a longshot, I thought I'd ask the board for suggestions.
Engine warms up nicely and stays at operating temperature (middle of gauge). I even have a backup digital coolant temp which reads 80 C when cruising down the highway. Yea thermostats are cheap but I live up here in the sticks where diesel e28's are not an everyday sight and parts have to be ordered in so just thought I'd ask the board and see if anyone has had a similar situation. As far as the heater valve is concerned, what I have determined is that it is normally open but closes when a cool cabin temperature is selected (0v at connector on warm selection, 12v at the connector on cold selection). It's a strange problem but your right, stupid of me not to just pop a new thermostat in and see if that changes anything.
From what you're describing, I'd be more likely to throw a heater-valve rebuild kit at it. Seems like the T-stat is working fine. Your problem is textbook for the heater valve. They're a bit more expensive than they used to be but $40 ought to get one to you. That amount used to buy the whole valve not five years ago. 
The heater valve is where i thought the problem was too (it might still be) but I took the one off of a parts e28 that I have and it operates the same as the one on the TD so I just put it back together thinking there is some other problem. (hell maybe they're both bad but they open at 0 volts and close at 12 volts so I thought they are both ok). Prior to asking the board I did check at getcoolparts.com for the valve and noticed the rebuild kit is 38 and change and a entire valve is 200 some. Probably best to start throwing money at it soon to get the damn thing working - supposed to be hovering near 0F here come monday. At those temperatures without a heater, I might as well be riding the R90/6!!
problem solved
heater valve changed with one from parts car - working great now - able to doff the long johns. thanks
interesting... I tested mine per the bentley, and it appears to work fine via the electrical test as described, I even pulled the heater valve, and confirmed the plunger extends to close the valve when I want it closed, and retracts to open it. The Bentley even suggested a clogged screen, so I cleaned it with no luck, and then I everything else is tested OK, maybe removing the screen would help?
jowjup - did your open and close (per bentley, listen/feel for it...) when current was applied/removed?
In looking at the design, the only other theory I have is that the solenoid is weakened to the point that it can't hold itself open against the rush of warm water, and that is pushing it closed and preventing warmth. Could this be the case?
jowjup - did your open and close (per bentley, listen/feel for it...) when current was applied/removed?
In looking at the design, the only other theory I have is that the solenoid is weakened to the point that it can't hold itself open against the rush of warm water, and that is pushing it closed and preventing warmth. Could this be the case?