So I really need some help with this.My cars a 92 w/3.1.So a couple years ago I had to replace my radiator and when I did my heat stopped being hot,everything seems to work fine and I even bypassed the valve and ran the water pump line directly to the heater core and still no heat.I can hear the vacuum kick on when I switch between vents and defrost and I flushed the incoming and outgoing lines from the core and replaced the water pump cause it was leaking.Still no heat.If anyone has any ideas it would be greatly appreciated.Thanks

 

Is the temperature control door actually working, or is the lever broken off of the shaft, like mine is?

 

I guess its possible,Ill have to take it apart and dig around.

 

Probably the easiest part of the HVAC system to check... Remove the lower hush panel on the passenger's side and the lever is almost literally right there. It is also possible that the cable broke or became disconnected at one end.

 

Ya I found it and verified it is working,I shoved my hand up there and felt the door opening and shutting.I did notice while I was driving last night that when I turn off the heat and switch to cold that my motor temp goes from about 180 to 220 so the heat is going somewhere just not in the car.I also took a look at the heater core while I was there and it looked fine.No puddles on the floor.I did top off the radiator yesterday it was a little low.I dont know whats going on.thanks for the idea.

 

Can you give a better description of how the core is bypassed? Maybe a pic?

 

It wasn't the core I bypassed I took out the valve in the engine bay with the vac line attached to the top and ran the coolant directly to the heater core.I did this because I thought maybe the new valve I had bought was bad. It didnt seem to help.I am wondering if changing my thermo to a higher degree unit will help. Ive kinda ran out of ideas aside from just swapping the core and hoping for the best.(really dont want to though)lol

 

I know next to nothing about HVAC, but a stuck open or incorrectly functioning thermostat could keep the engine coolant flowing in which case it simply won't rise to a temp high enough to have heat, thats why people don't often put 160 degree tstats in for cars that drive in the winter. Easy way to check this is to watch your engine temp guage, if it never moves or stays really low I'd check the tstat.

 

I think we need to see this... I can't be the only one .

 

I was using copper water line in a y config to bypass the valve.Now that I think about it that probably did not help since it wouldnt circulate.lame

 

I can see why you wanted to delete the HCV. However, all you needed to do was to run a pipe parallel to the upper heater core extension pipe running down the frame rail to the upper port on the heater (from the pipe running behind the alternator from the intake to the upper heater core pipe), and the lower port on the heater continues to run into its pipe back to the hose leading to the water pump.

 

So I reconfirmed the vac to the valve in the engine bay and ran the motor till it was hot.I then checked the two lines to the core. the lower one seemed warm but im not sure it was from the water pump I kinda think it was from the exhaust manifold.The reason is that I felt the rubber hose from the water pump and it was hot then felt the y pipe connecting it to the lower line and it was warm but after the that it was way cooler and the upper line felt as though there was no fluid going through at all.When I flushed those lines I only did the two lines that are connected to the valve not the y to the water pump.So im wondering if the y could be clogged and not letting the fluid circulate.I just dont know what way the fluid flows through the core.Im assuming its from the lower line to the upper line.Any insight? Thank you for all your help thusfar.

 

There isn't supposed to be a Y on the outlet side... Just like the radiator, the hot coolant comes from the intake at the top connection (where the valve USED to connect to the engine behind the alternator), and comes out the bottom and goes into the water pump. I'll have to see if I can get some pics tomorrow of what I mean. BTW, when you checked the core today or whenever you did it, did you make sure the heat selector was on HOT? Did you check to make sure you have a vacuum signal to the valve with the selector on COLD? Lack of vacuum to the valve opens up the coolant supply to the core, and vacuum closes it. Is the vacuum switch on the temperature lever at the control head working?

I'd still like a pic... It would help to fix this.

 

Ok so the vac is correct its on when cold is selected and off with heat.If I get what your describing the fluid should run from the valve under the ttstat to the selector valve into the line to the core then back to the valve and water pump? Ill gte a pic taken so you can see.

 

Heres some pics.That top hose on the left of the valve in pic 3 runs down to a y that runs to the water pump to the right and the core to the left.I thought I had the hoses backwards but they only go on one way.

 

Next time you run the engine, feel the 2 lines running to the core itself, on the bulkhead (between the distributor and the heater box). If everything is working, both lines should be hot, but one should be slightly cooler than the other because the core has cooled the fluid off slightly. If one is hot but the other isn't, check to see where it comes from. It's possible that one or the other of the inlet pipes is clogged. I'm not sure how the HCV bypasses the coolant flow to the core... I would assume that the one line that t's into the other is just welded to the other pipe in a way that the coolant flow stops at the end of the pipe, and that the diaphragm inside the valve releases the internal valve, letting it drop and uncovering the lower port to let the coolant flow to the core. Did you say you blew out the solid lines running to the core? If not, try doing so on the inlet pipe (the top one that runs between the HCV and the core)... Sounds to me as though you have a clog in there which is blocking coolant flow to the core. Just make sure you have the hose at the bulkhead disconnected so you don't blow the crap (if any) into the core and clog that up. Also, you can disconnect the inlet hose at the core and see if any coolant runs out or the line running to the HCV (not the core... sounds as though the core is probably receiving coolant from the water pump). Be warned: if those hoses haven't been removed from the core pipes in a while, they may not want to come off easily.

:edit: Also, have you replaced the heater core? I know it's a royal pain to get at, but that may be clogged as well, if it's receiving coolant as per above.

 

The A/C heater system diagram in my FSM is too crowded to show anything, but I might be able to post a pic of the basic non-A/C heater hose routing so you get an idea of how it's supposed to work, if you like.

 

So I just pulled the ttstat housing and the valve under it,the valve below was completely clogged with crap.No flow whatsoever.Gonna put a new one in tomorrow.Im also gonna bypass the throttle body while im at itThanks for all your advice.Im hopeful that this will solve the problem.

 

I figured the system was clogged somewhere. A word of caution: When you replace the heater pipe adaptor (or whatever it is called), DO NOT LOSE THE O-RING! You'll end up going to the parts store and getting at least 3 to seal it, and then it's a real pain to get back together. Also, do NOT break that white or black clip that holds the pipe to the adaptor, or you'll have a leak and you'll need to get another adaptor (or reuse the old one).

 

I've got heat!Thanks for the tip about the o ring I didn't even know it was there till you mentioned it.I found it by the hood latch it must have went flying when I pulled out the pipe.

 

The reason I mentioned the o-ring is because that's what happened to me and it's a real pain to deal with when that white clip breaks (happened twice now).