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No heat from a 1992 Chevy Lumina.

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New User

Oct 6, 2013, 11:08 AM

Post #1 of 3 (2119 views)
No heat from a 1992 Chevy Lumina. Sign In

I have a 92 Chevy Lumina with a 3.1L that I can get very little heat out of. It had 218K on it when I bought it with a bad head gasket or a cracked heading August of 2009. I replaced the heads with a set of a 93 Lumina. I also did a thermostat, radiator hoses, and heater hoses at that time. The heater never really worked well when I got done. The next summer the side tank on the radiator started leaking so I replaced that.(entire radiator) I took it to a dealer and they claimed my thermostat is weak but being less then a year old I didn't worry about it. They flushed the heater core and it didn't help any. When I check the thermostat with a raytech gun it says its 185 degrees so it can't be far off. Last winter I checked it and it was only coming out of the vents at 80 degrees. Somewhere in the last two years I installed a new heater core. The other day (now 3 years and 50K later) I had a steel line that goes from the top of the water pump to the heater core so I decided to put it in and in the process I was going to check the water pump flow, I never checked this before because both lines were getting hot (inlet and outlet at the heater core) but decided since things were being pulled apart that it'd be the time. Out of the top of the pump I got very little to nothing at less then 12" over the top of the water pump. I thought well ummmm maybe I better pull the pump as I've heard stories about the impellers getting ate off by acid in the antifreeze. Took the pulley off and it looked like a new pump. Sure enough the pump looks like new on the backside as well. I put in a different style pump just to see if that'd make a difference and it didn't. I checked the other side of the line thinking the flow may be coming the other way through the heater core and I didn't get anything. I put it all back together and it seems to be working a very little bit better but not like it should be at all. My question is which way is the coolant suppose to flow through the heater core? Does it go from the top of the water pump to the heater core back to the nipple on the backside of the lower manifold, or does it come out of the nipple in the manifold by the thermostat to the heater core back to the water pump? Is there anything in the front cover that may have gotten messed up while I had it off that would cause a no flow issue? The motor has never ran hot in the 3 years and 50K I've put on the car. The cover looked fine when I pulled the pump out on the inside. Has anyone ever seen a nipple that goes into the lower manifold get plugged? Is there anything that's just plain and simple I'm way over looking? is there anyway I can check the flow through the heater core going through the nipple? Or is it just as easy to remove the nipple and look at it? I know the restrictor piece inside is pretty small. Thanks for any and all your help everyone.

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Oct 6, 2013, 11:30 AM

Post #2 of 3 (2106 views)
Re: No heat from a 1992 Chevy Lumina. Sign In

Hmmm? Heater hoses hot to the touch and 80F output temps: Suggests air flow thru core is mixing with ambient air. Diverter/blend door problem or perhaps new core if it didn't fit well isn't in place tight?

T-stat housing really should read real close to the rating of the t-stat ~ 195 is most common but 10F more won't make our heater feel much better. Most run 125F or more, low fan (more residence time) out low heater ducts.

Not sure you can mix up heater hoses to core easily. Some molded and wouldn't reach and many different sized the smaller would be the input side if different.

Restrictions in return to engine if hot coolant was staying too long would take most all the available heat out of that coolant.

Make sure it's truly full of coolant, no air or vapors in engine radiator not just a recovery tank. Way too concentrated antifreeze (too strong) doesn't help but your symptoms don't reflect that,


New User

Oct 6, 2013, 12:08 PM

Post #3 of 3 (2100 views)
Re: No heat from a 1992 Chevy Lumina. Sign In

Thanks for the reply Tom. I was wondering about the heater core mixing with ambient temps. The a/c in the summer is ice cold. It doesn't take much to cool the car off and the blend door seems to work perfect in the summer with the a/c. I even disconnected the actuator and flopped the door by hand and it sure sounds like you can hear a thump when it was fully closed. Unless it's thumping against something else. The new heater core seemed to fit good I can't remember anything that made me curious to think it was going to leak air. When I pulled the old one out I looked it over and it didn't really seem like it was bad. It was a common question to have you replaced it yet so I just did it so I could say I have.

The car is running a 195 thermostat and when I check it, it's around 185 so yes the 10 degree loss is not to bad to me. it should definitely put out more heat then that I'd assume.

I know the heater hoses are in the right spots compared to my cutlass that has the identical set up. But that heater is like a sauna, it will cook you out in the middle of winter. I'm just unsure which way the fluid is suppose to flow, to be able to check this whole pump deal. I'm assuming from other things I've read, you should be able to hold your return line up at least a couple feet about the pump and still have good flow. Which side is the return side?

If I remember right, there is only like a 20 degrees difference in my cutlass and there is like a 30 or 40 degree difference in the lumina from the input and output on the core. But I don't remember which was to the core and away from the core, to check flow. I'd go check my cutlass but it's tore apart now too.

Thanks again.

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