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Discussion Starter · #1 ·
hey guys, Ive done a lot of research on a bunch of different forums but I can’t seem to find a thread that replicates my issue. Im gonna take a shot and hope I can find some answers here.

I have a 1992 LX, 5.0 5 speed, carb swapped. nothing is done to the engine besides a cam and intake. Running under drive pulley’s as well. Everything except for the engine itself is brand new. all accessories, pulleys, thermostat etc has under 10k miles on it.

my current issue is I have very little/ lukewarm heat. I’ve noticed if I let the car run without the blower fan for a good 10 mins then turn it on, very good heat comes out. but after about 15 seconds it will eventually dissipate and blow cold again.

For the record: I have a 180° thermostat, mishimoto 2 core Radiator, LMR’s electric cooling fan kit.

Things I have discovered/ tried to do:
1) blend door seems to be functioning properly, noticeable difference from hot/cold even without working heat
2) the inlet to my heater Core sits around 180-195° according my infared gun. outlet will be the same temp, until I crack the fan on. The outlet hose will drop to 150° once the blower motor is on.
3) I have attempted to flush out the heater core twice. both times no gunk really came out, the water seemed to flow pretty well.
4) my cooling system seems to be fully operational. it builds pressure, doesn’t overheat. The temps range anywhere from 180°-195° Depending on driving conditions.

my Only educated guess is coolant isn’t flowing through the core fast enough, but can’t figure out why/or how.
 

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hey guys, Ive done a lot of research on a bunch of different forums but I can’t seem to find a thread that replicates my issue. Im gonna take a shot and hope I can find some answers here.

I have a 1992 LX, 5.0 5 speed, carb swapped. nothing is done to the engine besides a cam and intake. Running under drive pulley’s as well. Everything except for the engine itself is brand new. all accessories, pulleys, thermostat etc has under 10k miles on it.

my current issue is I have very little/ lukewarm heat. I’ve noticed if I let the car run without the blower fan for a good 10 mins then turn it on, very good heat comes out. but after about 15 seconds it will eventually dissipate and blow cold again.

For the record: I have a 180° thermostat, mishimoto 2 core Radiator, LMR’s electric cooling fan kit.

Things I have discovered/ tried to do:
1) blend door seems to be functioning properly, noticeable difference from hot/cold even without working heat
2) the inlet to my heater Core sits around 180-195° according my infared gun. outlet will be the same temp, until I crack the fan on. The outlet hose will drop to 150° once the blower motor is on.
3) I have attempted to flush out the heater core twice. both times no gunk really came out, the water seemed to flow pretty well.
4) my cooling system seems to be fully operational. it builds pressure, doesn’t overheat. The temps range anywhere from 180°-195° Depending on driving conditions.

my Only educated guess is coolant isn’t flowing through the core fast enough, but can’t figure out why/or how.

Under drive pulleys. Do you have heat at higher rpm? Probably pulling more BTU's out of the heater core than you're inputting; at the flow rate your under drive pulley creates at idle. That was a mouthful.


Really should have a higher thermostat in the car too IMO.

What emissivity setting do you have set on your IR gun?
 
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Discussion Starter · #3 ·
Under drive pulleys. Do you have heat at higher rpm? Probably pulling more BTU's out of the heater core than you're inputting; at the flow rate your under drive pulley creates at idle. That was a mouthful.


Really should have a higher thermostat in the car too IMO.

What emissivity setting do you have set on your IR gun?
There is more heat at higher rpm, but it’s not really that noticeable. But, I’m glad you said underdrive pulley’s. At one point I was shifting the blame towards them, but I could never find any threads/articles supporting my guess. I talked to an LMR rep a while back, and when I asked if underdrive pulleys could cause the issue he disregarded it. Said that the underdrive pulley’s wouldn’t make that much of a difference in regard to coolant flow. Which didn’t make much sense, considering what underdrive pulleys do. But I figured they knew better than me.

I was thinking about going with a 195 stat. it hardly runs over 180° after I put that new rad In.

truthfully, I don’t know what emissivity is. So I’m assuming my gun doesn’t have that. It’s just one if those cheap $30 laser thermometers. You just click the trigger and point it.
 

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truthfully, I don’t know what emissivity is.
The emissivity setting tells the sensor how emissive the surface is, and improves the accuracy of the measurement when it is set correctly.

Different materials have different thermal emissivity characteristics (Kinda like escaping or reflecting heat).
 

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Yeah reason i ask is a 30 degree drop across the core is fairly substantial. If we knew the actual flow rate we could calculate how much heat is coming out of the core.

Holding everything constant, the flow rate plays a large role in how much heat is removed from the coolant (assuming the air from the blower is capable of removing this heat).


The confusing part is you said 150f was the exit temp, id assume you'd have a fairly hot air coming out of the heater still. Questioning the measurement because of this.
 
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I talked to an LMR rep a while back, and when I asked if underdrive pulleys could cause the issue he disregarded it. Said that the underdrive pulley’s wouldn’t make that much of a difference in regard to coolant flow. Which didn’t make much sense, considering what underdrive pulleys do.
Of course, they wanted to sell you an underdrive pulley set. It's similar to many of the CAI brands that tell you that it instantly makes power on its own even though that's completely untrue unless you have substantial induction mods already done first. Your electrical system and a/c system can also suffer from underdrive pulleys under high system demand. If it were my car I'd get rid of them.
A 180° thermostat is not needed or beneficial unless maybe you live in a far southern state or other hot area but along with your upgraded radiator, electric fan, and underdrive pulleys it's definitely going to make your car run too cool.
 
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