Crazy CCU no aux pump or valve st8 and little heat? - PeachParts Mercedes-Benz Forum

argus445 · #1 11-10-2007, 10:07 PM

I've been working on the ccu since my heat stopped working when it got below freezing nice huh? the aux pump was fried so i hooked it up all st8 with a piece of xtra long hose bypassing it. Then i checked thermovalve it seemed to be working ok no problems there but after couple weeks of it working sometimes sometimes not so much i bypassed it too running piece of hose from the two metal pipes so that rules that out? The best i can get out of the vents is 80 degrees on low fan when i go to max the temperature drops off is there an external vent door or something letting cold air into it or is it simply not enough flow thru it w/o the aux pump? i recently flushed the heater core out too thinking it could be restricted seems to be ok flow wise just having heat sometimes sometimes not any suggestions? I took the glove box out and moved the different positions all the valves seem to be moving and opening closing but still sometimes going down road my heat will suddenly go out or when i increase the fan speed above min it drops off? thanks

Gil · #2 11-10-2007, 10:12 PM

Your post rambles everywhere - not sure exactly which problem you're working on or what the most important question is.

Does your CCU function properly?

Have you tried swapping it out with another unit?

argus445 · #3 11-11-2007, 11:18 AM

Quote:

Originally Posted by Gil

Your post rambles everywhere - not sure exactly which problem you're working on or what the most important question is.

Does your CCU function properly?

Have you tried swapping it out with another unit?

No i don't have another unit basically heat only works when the fan is in min and when i increase the blower speed it gets cold and i have both the aux pump and the thermovalve bypassed so it's running coolant thru all the time so should be bloody hot as it could be like 140-180 degrees and it's only like 80 degrees. And my heater core is no plugged so i'm stumped?

Gil · #4 11-11-2007, 12:04 PM

I'm not the expert at this, but here is my estimation: the first thing you want to do is make sure you've got enough coolant in the system. If one of the heat hoses (or perhaps part of the heater core) is empty or nearly empty, then blowing more cold air over it will only make things colder.

If air passing through the heat vents was somewhat warm at lower fan settings, you might be getting a just a trickle of water through the heater core, but not enough to stay warm when you ramp up the fan speed.

Also, if I remember correctly, the auxiliary pump keeps water pressure at proper levels, especially when idling. If you disconnected the pump, it may not provide enough pressure through the system to keep hot water in your heater core. Not sure why you needed to disconnect it in the first place.

Therefore, first ensure you have enough coolant in the system. If not, you could have some kind of blockage in a heater hose or in the core itself. I would recommend properly connecting the monovalve and all other parts in working order to be sure, but someone with more expertise may have another solution.

mobetta · #5 11-11-2007, 10:50 PM

"so i hooked it up all st8 with a piece of xtra long hose bypassing it."

mabbee you have an air bubble in this hose? that could affect your flow.

I dont think that there is a door, temp is controlled by the monovalve which controls circulation

I think the electric pump is mainly to boost circulation at lower RPM's.
However, I think I have a spare pump around here somewhere. PM me if your interested.

argus445 · #6 11-12-2007, 07:01 PM

Quote:

Originally Posted by Gil

I'm not the expert at this, but here is my estimation: the first thing you want to do is make sure you've got enough coolant in the system. If one of the heat hoses (or perhaps part of the heater core) is empty or nearly empty, then blowing more cold air over it will only make things colder.

If air passing through the heat vents was somewhat warm at lower fan settings, you might be getting a just a trickle of water through the heater core, but not enough to stay warm when you ramp up the fan speed.

Also, if I remember correctly, the auxiliary pump keeps water pressure at proper levels, especially when idling. If you disconnected the pump, it may not provide enough pressure through the system to keep hot water in your heater core. Not sure why you needed to disconnect it in the first place.

Therefore, first ensure you have enough coolant in the system. If not, you could have some kind of blocpkage in a heater hose or in the core itself. I would recommend properly connecting the monovalve and all other parts in working order to be sure, but someone with more expertise may have another solution.

The pump was fried hadn't worked in years by looks of it. I just wondered if there was a outside air door that could be open i guess it's just crappy design from what i've heard seen gathered

#7 11-12-2007, 07:22 PM

If you are actually getting coolant flow through the heater core, you should be getting plenty of heat. This car does not have a blend door like some domestics. Are the heater hoses hot when it's running? Is the engine getting up to full temperature (80C)?