: No heat inside the car



Wilk
05-13-04, 10:54 AM
I recently replaced the water pump on my '99 seville, and occasionally I dont get any heat inside the vehicle. It seems that if I overfill the surge tank it will heat, but now it wont even do that. Its almost as if the core is air locked, is this even possible. Of course this happens at the worst times possible, like when my cold blooded wife is an hour from home, or just leaving to go somewhere.

Geno Castellano
05-13-04, 02:37 PM
Is the system full of coolant and is the water pump turning correctly? When the pump was replaced did you check the water pump drive belt and the water pump belt tensioner to make sure it's good and that the tensioner is properly tensioning the belt so that the water pump turns?

It's possibly the thermostat sticking open. Especially if you just were in there working on the water pump and that area. Something may have jammed the thermostat or caused it to stick open and not heat up.

The heater core flow is direct off the engine coolant crossover and returns directly to the water pump inlet so the heater core gets flow no matter what if the water pump is turning and the system is full.

You might check the heater hoses for kinks or something. You can discconnect the heater hoses fairly easily. One is at the right rear of the engine immediately off the water crossover toward the firewall and the other is at the water pump inlet - that 1 inch hose off the thermostat housing. Disconnect and flush with a garden hose to see if the system is free.

You did refill with DexCool, correct? If you used the green silicated coolant to refill there is a slight possiblity of silicates parcipitating out of solution and blocking flow to the heater core. Flushing and refilling with the proper coolant should alleviate this problem.

With the engine cold, go to the pressurized surge tank. Find the small, 3/8 hose coming from the engine and disconnect it at the surge tank. Start the engine. Coolant should piss from the hose in a steady stream. If not, go to the upper radiator hose connection to the engine and find the other end of the 3/8 hose at the nipple by the radiator hose on the engine. Disconnect it. Start the engine and coolant should piss from the nipple on the engine (actually it's a hollow bolt) If not, remove the bolt and determine what the restriction is. This is the vapor vent line for the water pump. If it's not flowing constantly the water pump can accumulate vapor and vapor lock and stop pumping causing no heat and overheating at the same time.

Wilk
05-13-04, 03:01 PM
I seriously appreciate your help. I rebuilt this car from a wreck, and its been nothing but a pain in my you know what. AC compressor went out recently, replaced it with a used one, thats no good, get to do it again. Then the heater stops. Did I mention that removing the ac compressor is a day job.

Pretty soon the wife will get pissed and tell me to build her something else, dont have time for that.

I did use dexcool. Pump is turning, cant answer the t-stat, but its not getting overheated.

Geno Castellano
05-13-04, 11:36 PM
I seriously appreciate your help. I rebuilt this car from a wreck, and its been nothing but a pain in my you know what. AC compressor went out recently, replaced it with a used one, thats no good, get to do it again. Then the heater stops. Did I mention that removing the ac compressor is a day job.

Pretty soon the wife will get pissed and tell me to build her something else, dont have time for that.

I did use dexcool. Pump is turning, cant answer the t-stat, but its not getting overheated.

Check the vent line and thermostat as recommended.