Heater probs

March 27, 2007, 10:01:19 AM

I hope somebody can help me out here a little bit. I am trying to help my friend fix his 1989 cougar with a 3.8. It has a couple of problems. 1. The heater does not work. now i think this might be the heater core because i had the same thing happen to my cougar. Is there anything else this might be? 2. He says it seems to running hotter than it is supposed to be, now the rad has been changed and the thermostat as well with no avail. What temp should this be running at? Thanks in advance for any help
Jonas

Heater probs

Reply #1 – March 27, 2007, 10:18:57 AM

Well for the heater it could also be a problem with the flaps under the dash that direct the heat to the vents. I know in the Stangs they are powered by vacuum motors but not sure on the T-bird. When you move the heater controls from position to position do you hear some hissing noise and movements of flaps? That would indicate they are moving correctly. (This side of a dead mouse or pencil stuck in one.)

On the engine temp typically in the 190's but not sure of specifics for the 3.8l. Did he replace the thermostat himself and if so did he burp it correctly? I know on the 5.0s if not burped correctly you can develop an air pocket around the thermostat resulting in it not opening when it should. A small bypass hole drilled in the top of the thermostat helps avoid that problem. Could also be a timing problem as that can cause it to run hot also. And has he actually measured the water tempture or is he going off the dash reading? Because the dash is known to not be that accurate.

Just a few random things to check.

Bryan

Heater probs

Reply #2 – March 28, 2007, 06:38:17 PM

ok thanx i will try and keep you updated

Heater probs

Reply #3 – April 01, 2007, 09:32:25 AM

Ok, now here's a problem I'm definitely familiar with. I too have the 3.8 in my '86.

On the heater not working, odds are, the heater core is choked up with crud, ESPECIALLY if appropriate coolant hasn't been maintained. The 3.8 seems to be extremely sensitive to coolant mixture because of all the different metals. You have brass (radiator and heater core), aluminum (heads/intake) and cast iron. When you combine all that with coolant that is slightly caustic (for cleaning purposes), you get a fantastic battery, albeit, a very low voltage one. Now, leave this sitting still for a little while, and the corrosion will start, which is the VERY reason for the cleansing agents in the coolant. There are lots of brands of coolants on the market now that are a "universal" coolant. These tend to work best in the 3.8's and minimize corrosion. If the radiator had crud in it, any that broke loose went straight to the heater core, and that's where it will stop. The flues in the heater are a lot smaller than they are in the radiator. Sometimes, you can get the blockage cleared by reverse flushing the core. More often than not, you're looking at replacing the core. Try the reverse flush first, because putting a core in a Fox AIN'T fun. Disconnect the hoses at the water pump and run clean water through the core. If you get any significant back pressure in the core, it's plugged. Swap your water supply to the other hose and try again, and see if any crud comes out. That stuff tends to set up in a core like concrete, so I wouldn't get my hopes too high.

I also experienced the high temp readings with a new rad, t-stat, hoses, etc. Part of that was the burping, but somehow, I really didn't feel like it was getting that hot. I work in heavy industry, and managed to get my hands on a laser temperature detector. Turns out, the engine was quite cool, around 185, (t-stat should be 187 for proper EEC operation) but the gauge was pegged out. There is a small voltage regulator on back of the instrument cluster aptly called the IVR. These things fail on the high side, and over-drive the temperature and fuel gauges, assuming you have the base hybrid digital cluster. I've seen a retromod in here using relatively cheap parts from Radio Shack which gives you an adjustable supply for the gauges. This lets you set the gauge where you want it for a given temperature. Normally, when the engine is at operating temperature, the gauge should read about half scale.

My problem got solved when I let a stealership install a long-block for me. When I took the car in, I drove in jammin out to ZZTop on the OE radio/cassette on a Monday after driving from Kentucky to Alabama on the previous Friday. Somehow, when it was time to pick up my bird, I had a dead alternator, dead stereo, and no speedo. I noticed after finding all the dead electronics, that there were new battery clamps on the OE cables. The OE Cables on mine were BOTH black, and would reach EITHER battery post. Hey, it came that way, what can I say? I'm the OO on this car, so I KNOW the cables had never been replaced. Something tells me they connected the battery backward and hid their blunder as best possible. Thank goodness the EEC is protected by diodes. I found an 87 in a yard, and got the cluster from that, and bingo, speedo works, gauges read "right" and all is good after replacing the stereo with aftermarket.