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No HEAT!

Hello all:

Got no heat in my 1995 Chevy Lumina passenger car with 3100 engine. Have replaced thermostat, water pump and replaced freeze plug that had a pinhole in it. Heater still blowing cold air and temp gage only moves slightly - stays in low range never reaches normal operating temp. Can anyone help me identify what’s causing the problem and how to fix it?

Thanks,
Karanja

Was The Cooling System Properly Purged Of Air ?
CSA

Yes, did purge the system.

If the temp gage barely moves, you’re not gong to get hot air out of the heater system. First you need to figure out why your engine isn;t warming up and correct that.

Possible cause of an engine not heating up are

  1. a stuck T-stat (I did notice that yyou already changed that)
  2. low coolant (see CSA’s question)…did your purge the system?
  3. extreme winter temps…like we had in ND when I lived there. We had to upt carrdboard in front of our radiators to get the engines to warm up. Where do you live?

Also, if when you purged the system you did not have the heat on, you’ll still likely have air in the heater core. You need to turn the heat on to open the valve that allows the coolant to flow through the core (and purge the air) on many cars.

Unless you had some other reason for changing the water pump (?), that would not be expected to help. It is good, however, that you found that pinhole.

Sounds like an improper or defective thermostat…

Do The Heater Hoses Feel Hot Where They Pass Through The Fire Wall ?
Both Hoses ?
CSA

Thanks much for the responses guys.

Not doing the work guys, but:

Yes CSA, at least top hose from manifold to heater is hot.

In Detroit, MI, coolant level good, not sure about heat being on during purge but will check/do mountainbike. Also, temp gage fluctuated up and down (never overheated) as did the low level of heat - at that time - as a result it was recommended that water pump be changed.

Temperature Gauge Fluctuating Up And Down Is Most Likely An Indication Of Air In The Cooling System Needing To Be Purged.

If you can’t get the air out and heat flowing then you might have to pressure test the cooling system to be sure it holds pressure over time to check for possible external/internal leaks.

CSA

It sounds like there’s still air trapped in the cooling system.

To make sure there’s no air trapped in the cooling system, drive the vehicle to get it at as hot as possible. While the engine is idling, loosen the upper radiator hose clamp and then take a small flat bladded screwdriver and insert it between the upper radiator hose and the radiator hose neck. Allow the engine to continue to idle until all the air is purged out of the cooling system and nothing but coolant comes out. Remove the screwdriver and retighten the hose clamp.

Tester

Are you sure the radiator is full of coolant?
It is entirely possible to have a full reservoir and a radiator that is NOT full.
Are you absolutely sure the correct water pump was installed?
If the pump is “turning the wrong way” you’ll have a problem.