View Full Version : Heater problems on my 96 FWB Any advice?

03-21-06, 05:32 PM
I'm apparently having some kind of trouble with the heater on my 96 FWB. When I got the car less than couple weeks ago, I used it a couple times and it seemed to work fine. It's been cool and/or overcast the past few days and now I can't get it to warm up right. I let it warm up today, giving it ample time, before a short trip and when I got in, it was still blowing cold air out on the left side of the dash. I can set it on auto or economy and still the air blowing out isn't very warm. It does seem to warm up just a little driving it in the 18 mile round trip. I'm setting it on 85-90 degrees too. All the functions of the control panel seem to work fine so I don't know what the problem is. It's almost as if the hot water isn't circulating through the core. Does anyone have any input? I hope it's something I can work out without a lot of hassle or cost. Just my luck....At least it won't be much longer before I won't need a heater.


03-21-06, 10:45 PM
First, go to pointer 24 and read the coolant temp.

To do, press OFF and WARMER and hold till light test shows. Once it goes to 00, then press the fan up or down button till you get to 24, then press outside temp button. This is coolant temp in degrees C. It should be around 80-90C.

If not ok, replace tstat, then do the following:

Give the heater core a flush. Just disconnect the hoses on the pass side of the engine, bring out the garden hose, flush it out some. Blow the water out, fill it with CLR let it sit for 10 min or so, then flush each side alternatively till it blows clean.

03-22-06, 01:44 PM
Before you go through the trouble of flushing the system you may want to try a quick and semi-easy possible fix. The LT1 engine has a closed cooling system, meaning that air in it is a bad thing. Any time the cooling system is opened (new heater core, water pump, t-stat change, etc) the system must be bled via the bleeder screw located on the top of the t-stat housing (mounted on top of the water pump). Turn you heat on full blast in the car and wait for the t-stat to open (get car to operating temp) -- it's also best to be parked on level ground.
With the engine running, crack open the bleeder screw and look fo any coolant coming out. The goal is to let the air out but then close the screw anytime you see coolant. Theoretically the air is supposed to collect at the stat housing so you can easily bleed it out -- but in the past I have found the air to be stubborn and it takes several occassions of bleeding to get ALL of the air out. It may take several days of bleeding.....

If you still do not get sufficient heat then I would follow NODIH's suggestions and look at the climate panel for car's operating temp, t-stat condition, and then heater core flush. Remember that you will have to bleed out air if a flush or stat change is changed.

Another overlooked item that is low-cost cap on the overflow reservoir. It helps seal off the system and maintains a certain pressure and in the past I've known people to have bad caps which led to overheating issues and other problems.
Good luck!

03-22-06, 06:01 PM
Thanks for the advice guys! Another thing I forgot to mention is that the other day after driving it to town without the heater warming up right, I got out and put my hand on the heater hoses right back at the firewall. I can't remember which one was nice and warm but the one with the shield on it was cold right at the firewall side of the shield. I think that's the one closer to the engine because in front of that shield, it was warm apprently from the radient heat of the engine. It's never given the slightest hint at overheating, idiot lights flashing or anything. Peeking down in the plastic tank the coolant level looks fine and not a bit of rust.


03-22-06, 06:14 PM
My 94 FWB coolant temp drops when rpms are up, around 2500 rpm or so and higher, the coolant temp drops, I have seen it as cold as 47 degrees C after it was driving at 85C a few minutes before. Drop engine rpm down, and it comes right back. Get rpms up (say 65 mph in 3rd) and the temp drops colder and colder. Go back to OD and they return to normal.

No one seems to have a clue why. Scott Mueller suspects that I have a bad water pump and that is the culprit. There is a TSB on this "phenomonon", but I have performed this TSB and no help. This TSB is only on 94 models, 95-96 got a revised radiator and surge tank that eliminates that coolant line.

BCS71 is right, the LT1 is VERY suceptable and sensitve to air pockets, which is a key reason (other than losing the patent infringment suit) that reverse cooling has not maintained in production on the LS1 (although it looks like it was intended for it). Pontiac actually pioneered this cooling system back in 1955-1958 and warranty problems with it was its demise. They called it the "Gusher" cooling system, I believe all Pontiacs can still use it, but Pontiac used copper tubes inside the heads that eroded and starting causing pinging issues (hot pockets of steam in the heads).

03-23-06, 10:13 AM
Well, another phenomenon with the LT1 vehicles is the Dexcool changeover in 1996. I don't think the 96 FW escaped the new coolant....I know the B-bodies fell victim to it.

In 1996 GM switched over to the 5yr/100K mile Dexcool coolant. At the factory they threw in some pellets that dissolved and tested for leaks or something..... as a result the pellets collected in areas and caused clogs. This gave Dexcool a bad reputation when in reality it was the pellets that were added in that caused issues.

Bottom line, your heater core may be clogged with pellet junk..... Time for a flush!

03-23-06, 11:55 AM
Bottom line, your heater core may be clogged with pellet junk..... Time for a flush!

That was my solution to the same no heat symptoms. :thumbsup:

03-23-06, 10:37 PM
What is the best way to flush the rad on the LT1?

Lord Cadillac
03-23-06, 10:55 PM
I'm not sure if it'll work in your case but sometimes if you just keep the fans blowing full blast, whatever's stuck gets blown out. That's worked for me before... It's no fun in the cold, but that's when I did it as well...