SEVERE overcooling (1 Viewer)

[Sean Foster]

I’ve got a 91 cruiser with a 3fe. Over the summer I was battling overheating problems mostly by my own fault. Well now that it’s getting cold the thing will not get up to temp. A few days ago I got it up to 170 on my way to work, ambient is about 55 ish degrees. Well I replaced the thermostat, made sure to put that rubber o ring up top and replaced the fan clutch and now it realllly struggled to break 140. Same ambient temp and my heater produces absolutely no heat

 

[chappysfj40]

maybe stuck open?

 

[BILT4ME]

I’ve got a 91 cruiser with a 3fe. Over the summer I was battling overheating problems mostly by my own fault. Well now that it’s getting cold the thing will not get up to temp. A few days ago I got it up to 170 on my way to work, ambient is about 55 ish degrees. Well I replaced the thermostat, made sure to put that rubber o ring up top and replaced the fan clutch and now it realllly struggled to break 140. Same ambient temp and my heater produces absolutely no heat

Thermostat is stuck open. Even if it's new, or it's got something lodged in it. That's the only way an engine cant' get up to temp unless your sending unit is wrong and you're getting false readings. Use an IR gun to check temps in various places on the head and block to confirm they are within a few degrees of the gauge you are referring.

 

[Sean Foster]

Thermostat is stuck open. Even if it's new, or it's got something lodged in it. That's the only way an engine cant' get up to temp unless your sending unit is wrong and you're getting false readings. Use an IR gun to check temps in various places on the head and block to confirm they are within a few degrees of the gauge you are referring.

I’ll have to check the tstat, but I have an aftermarket gauge and the factory gauge and they both read dead cold. Heater doesn’t blow anything remotely warm so its sayin the same thing

 

[BILT4ME]

I’ll have to check the tstat, but I have an aftermarket gauge and the factory gauge and they both read dead cold. Heater doesn’t blow anything remotely warm so its sayin the same thing

How did you get all the air out of the system? An air pocket will make the gauge read COLD, that's why I suggest the IR gun. If the IR gun is within 10°F of the gauge, all around the head, the block, and the radiator, then the gauges are right and not reading an air pocket.

The heater not blowing warm can also be an air pocket.

Otherwise one of these with a stuck open tstat, will only hit about 150°F even if working it hard because 100% of the coolant is getting cooled while circulating. Otherwise, the tsat opens and closes based on thermal demand.

 

[bpenn1980]

Thermostat. Mine failed open Jan '20 while driving up the grapevine from valley to Gorman on I-5. Needle didnt budge. Pic below from flats just below grapevine when it failed. ABS unrelated.

 

[LINUS]

Another echo of the T-stat / fail open is the norm.

I bought a cheapie for an old VW that I never checked in boiling water in the kitchen.

Chased my a$$ for 2-3 days before Pops asked (1980’s - no internet).

Now I do the boiling water check even to OE ‘Yota ones - not falling for that one again

 

[Bludozer]

Thermostat is stuck open.

maybe stuck open?

I think I found the newest mod for all of the "oh god what do I do I'm at 220 in Moab" threads next July

 

[BILT4ME]

I think I found the newest mod for all of the "oh god what do I do I'm at 220 in Moab" threads next July

We had a 67 Camaro with a 327 that ran hot, so we pulled the Tstat out of it so it would run "normally". However, it was a seriously cold-blooded bitch to start when it sat overnight (carbureted) and took forever to warm up enough to have any heat for defrost. Of course, it was not really a winter-driving car....... (rear had Mickey Thompson N50-15's on it)

 

[Bludozer]

We had a 67 Camaro with a 327 that ran hot, so we pulled the Tstat out of it so it would run "normally". However, it was a seriously cold-blooded bitch to start when it sat overnight (carbureted) and took forever to warm up enough to have any heat for defrost. Of course, it was not really a winter-driving car....... (rear had Mickey Thompson N50-15's on it)

So what you're saying is...not the worst idea lol.

 

[BILT4ME]

So what you're saying is...not the worst idea lol.

No, it really isn't.

What it could cause is not enough heat, which will keep the computer in open loop and use a lot more fuel. It thinks it's still in the warm-up stage, so it keeps the pump on high and adds more fuel to increase heat, to get it to the closed-loop stage.

IT's worth a try, depending on time of year, a bit of expense of coolant, and hassle.

 

[clx16]

I ran mine without a tstat for several weeks. Would only get to 167. Yeah not a bad idea in my opinion. If i was far out and getting too hot. I would pull it and top off with more coolant or water and not worry at all.

 

[ChaseTruck]

So, from the cheap seats:
How about the old cardboard-in-front-of-the-grille thing? Time-tested, works well, can be fine-tuned; probably even highly sustainable tech

 

[LINUS]

So what you're saying is...not the worst idea lol.

I was on a tear as a kid of Rabbits/Sciroccos & a few GTI’s - blew a HG in one over near Spokane (~400mi from home) & just pulled the t-stat & refilled w/ water (summer) & dumped some milkshake oil 1/2 way & just topped w/ clean oil.

Got over the Cascade range pass & home, no damage to the block & head - did a new HG & that motor ran great until I wrecked it at Mt. Baker (snow) ~yr later & IIRC that motor went into another Rabbit body & did a road trip to the Grand Canyon & back.

 

[LandLocked93]

So what you're saying is...not the worst idea lol.

I'd say it's a great t-shooting step to take near the opening stages of the hunt to solve overheating problems when easier diagnostic measures are inconclusive. Determine the truck doesn't overheat in a full-flow situation and work backwards.

Selective t-stat operation would be a cool gizmo. Could work as a dash-switched valve in a bypass at the t-stat housing?

 

[leonard_nemoy]

My old 91 was the same way. As soon as the temps dropped below 60F it would never run above 150F and sometimes it would run around 135F or lower when driving in temps below 30F.

I went through the entire system and verified that my thermostat worked with the boiling water test. I ended up attributing it to the aftermarket aluminum radiator doing to good of a job.

When I was ice fishing or driving in really cold weather I would just slip a small piece of cardboard in front of the radiator. Enough to block about half of the radiator and it would run perfect, this was the only way to get the heater to work.

Does you rig have an OEM or aftermarket aluminum radiator?