Poor heater output / cool engine temp

[Ford Man]

I have a 89 SHO, 170K miles. I replaced the waterpump along with timing belt at 130K. I also replaced the heater core this past summer. The car has always ran extremely cool. I checked and replaced the thermostat most recently along with all by-pass hoses. The heater has in the past been adaquate, under par as far as Ford heaters go. Most recently I just can't get any heat out of the engine. Even with the radiator block off 3/4, the engine temp barely gets into the normal section on the gauge.

Any ideas or experience with simular problem???
Ford Man

 

[fricker66]

Your problem sounds like what I experienced when my thermostat stuck open. However, you indicated that you recently replaced the t-stat. So much for that idea..........

You didn't indicate if this problem exists under all conditions or if it just takes awhile to begin getting heat inside the car. I recently replaced the t-stat, antifreeze, and all hoses during a valve adjustment. I still drive about 5-10 minutes before I begin to feel ANY heat in the car. Also, it really doesn't amount to much until I get into city traffic. Probably a compound effect of adequate air flow through the radiator at highway speeds and deteriorating weatherstripping seals.

Not much help, hope someone else has a cure!

 

[sdpatt]

The thermostat is either stuck open with a slight bypass flow or installed backwards. What brand of T-stat did you install?

 

[93MTXSHO]

I know that you all are going to think that I'm crazy, but I experienced the same thing. My thermostat was a Ford and had also been recently replaced. The only way mine would put out any heat was to put the temp on 90 and hit Panel-Floor and turn the fan up as high as it would go. Even then the heat sucked. I had the PCM replaced because it failed. Ever since it has been replaced, even in 30 degree Ohio temps, my heater blows hot and strong. Are you losing coolant slowly? The crimped on heater hoses next to the block were leaking on my car, and that may have had something to do with poor heat output, but I don't think so.

 

[Sammage]

sdpatt:
The thermostat is either stuck open with a slight bypass flow or installed backwards. What brand of T-stat did you install?

sdpatt, what brand (and part #) of thermostat do you recommend? I heard you liked the Robert Shaw Gen 2 (part # 792-192?)...where do you find them? shrug

 

[sdpatt]

I recommend the Motorcraft parts. Unfortunately, Robert Shaw does not make the Generation 2 thermostat to fit the SHO, at least according to their cross reference. The Stants are cheap and cheaply made.

If the engine is not heating up to the NORMAL temperature range, the thermostat is the cause. If the temperature needle is in the NORMAL range and the climate control is not producing adequate heat, there is a problem with the flow to the heater core or the climate control dampers.