TBI Running Cold?

[dhcomp]

Ok, so my truck was off the road for a month or so with some running issues. A new ECM finally cured it.

The current issue is it is running cold.

I've got remote start, so i am very familiar with standard warmup times. I often set the heat/defroster, and let it warm up before i get in when its cold out. Normally, 5 min idling and its warmer than i can stand.

Now, let it run 10 min, heat is barely warm at all, temp gauge pegged at left (100˚). Drove on the freeway for 20 min, gauge barely registers, and heat is barely warm at all. If i drive it on the freeway for 30min to an hour, it hits about 1/4....whatever temp that is.

Motor runs like its warm, but if it was actually warm, wouldn't' the heat be warm? Checked temp at manifold, and at header tubes with a indirect temp probe. Forget temp readings, but they were consistent. At elbow of headers, temp was maybe 450? I forget, hot enough to make me think the motor is warming up.

I recently replaced the fan clutch with a Kragen one, and this is suspect. Last time i tried to check it, it seemed to be locked when the motor was cold.....when really, it should just be spinning free. Have a new Delco one to put on, but haven't installed it yet.

Also, replaced temp sending unit (between first 2 cylinders on drivers side), checked wiring, tested gauge. Gauge pegs when grounded.

Any ideas? If the t-stat was dead, it would get hot, and read hot on the gauge?

If the motor is actually at operating temperature, what would keep both the gauge AND heater from working properly?

Help me out guys, its cold out now and i want heat!

Thanks!

 

[Burbdood 74]

Any ideas? If the t-stat was dead, it would get hot, and read hot on the gauge?

Not all the time. I've had a couple of T-stats fail, I believe they were open, and not let the system build up heat properly. My wife's car is starting to do that in fact. It's fine in the summer, but come winter tme, the guage doesn't even reach the half-way mark and the heater is barely warm.

Your best bet is to take the T-stat out and drop it in a pan of water on the stove and bring the water to a boil to see if it's operating correctly.

 

[swettysblazer]

I agree with snuffy, thats a good way to test them too. What temperature stat is in there now, any idea?

 

[GalDemSuga]

@ about $9.00 a pop, just put a new TStat in

Not all the time. I've had a couple of T-stats fail, I believe they were open, and not let the system build up heat properly. My wife's car is starting to do that in fact. It's fine in the summer, but come winter tme, the guage doesn't even reach the half-way mark and the heater is barely warm.

Your best bet is to take the T-stat out and drop it in a pan of water on the stove and bring the water to a boil to see if it's operating correctly.

 

[Keitha]

It may have a fail-safe thermostat where if it does fail, it fails open - for obvious reasons.
I concure with the others: try a new thermostat.

 

[4xcrazy]

The fan clutches will be stiff when cold, once they get moving they will loosen up and work on thermal temps, if you bought one of that kind.

I have the heavy duty cooling clutch on mine, and it sounds like a semi truck for a few minutes when cold until the silicone gets to where it needs to be, once everything warms up you can hear it working when it needs to.

Another vote for t-stat here too, especially with running that cold. Sounds like it's stuck open.

 

[Fordum]

Thermostat or fan. Both would cause that. But, here is another idea. How is the coolant level?

I was standing on a deer stand one cold morning, and my cousin drove up in his 1500. Bitching because it was blowing cold air.
I popped the hood to check to see if it had a heater valve, and noticed that the overflow was empty.
Eased the cap off the radiator, no water.
We filled it up, the heat started working, and we spotted a leak in the top part of the radiator.

 

[chulisohombre]

thermostat stuck open,broken heater core regulator, or low on fluid.only things that it could be.the fan would not cause the engine to not heat up at idle.internal combustion creates more heat than that could overcome completely like that.

 

[4X4HIGH]

Couple things might be going on here. First as everyone has said the T-stat might be bad (failed in the open position). The next thing would be low on water/coolant, and the last thing could be that the cooling system is so good that with the cold temps we've had here lately the system just won't allow the engine to warm up properly (don't laugh because it has happened to me a few times). For people that live in really cold climates they sell wind screens that you cover a portion of the radiator to help the engine warm up during the winter months. If you haven't already checked the radiator temps with an IR heat gun now would be a good time to check things out.

 

[ktmoutfront]

My 4.3 in my Astro van started running cold. New thermostat fixed it instantly. Did not do anything else.

 

[dhcomp]

@ about $9.00 a pop, just put a new TStat in

This man thinks like I do.

Thanks for the help everyone. Sounds like I reasoned wrong, and should try the stat. Stat is only a couple years old, 195*

Thanks

 

[4X4HIGH]

This man thinks like I do.

Thanks for the help everyone. Sounds like I reasoned wrong, and should try the stat. Stat is only a couple years old, 195*

Thanks

Don't forget that just because a part is new that doesn't mean it can't be bad out of the box. I would test the new t-stat in boiling water and watch to see what temp it opens at.

 

[chulisohombre]

Don't forget that just because a part is new that doesn't mean it can't be bad out of the box. I would test the new t-stat in boiling water and watch to see what temp it opens at.

yeah ive had brand new ones that didnt open correctly.its good to test them before putting them in to make sure they open correctly.most of the time i just put em in and run it to see where it opens on the guage.its only 2 bolts to take it out if it doesnt open correctly.before you take the one out thats in there,you can try and queeze the upper rad hose when its hot and moving and you should feel the coolant moving through the hose to the radiator.

 

[4xcrazy]

Running too cold is an issue I was having with my Burb after I took it to Indiana last year, and of course, when it was still running..

being that it lived here in Phoenix most of it's life, I set it up with a 4 row radiator and heavy duty fan clutch, never went over 200*. When winter hit last season, I couldn't get the truck to even get up to the t-stat temp of 195*, was always about 175ish. Even after a new t-stat, and blocking the complete front of the grille area,,, leaving the radiator surface open for the fan to pull air through if needed, it STILL would run cold, then I blocked off half of the radiator with cardboard, right up against the radiator,,,no joy, slightly better, but still not up to normal operating temp..

I was almost tempted to install a high temp 210* t-stat, but then realized I was moving back to Phoenix, and then it quit working on me due to some electrical issue,, so now it sits, in the cold, all alone, without me

 

[70jimmy]

Yep T-stat for starters. My TBI motor has a flex a lite fan with no clutch and a 4 core radiator and still heats very well. I doubt your fan choice has anything to do with it.

 

[Fordum]

then it quit working on me due to some electrical issue,, so now it sits, in the cold, all alone, without me

Man, don't post stuff like that here. Especially when I'm online. I'm going to have enough trouble sleeping tonight after the time change without wondering what kind of electrical issue you have........

Or have you already posted and I missed it?

Oh, and for a sight unseen diagnosis..........Its a bad ground......

 

[dhcomp]

Don't forget that just because a part is new that doesn't mean it can't be bad out of the box. I would test the new t-stat in boiling water and watch to see what temp it opens at.

Has worked fine for the last couple years, the running cold is a new thing

Thanks!

 

[dhcomp]

Nailed it! Thermostat failed open.

F U kragen. Motorad brand.

Replaced with new staun 195˚.

Thanks guys! Heat rocks!

 

[AJMBLAZER]

After my 6.2L thermostat debacle a few years ago I bought several ACDelco thermostats from Rock Auto. The RIGHT part and more than likely will work.


Glad to hear you got it fixed. I'm late to the part but your situation sounds exactly like what my buddy's Toyota is doing. Been bugging him to fix it for two years now but his wife just drives through winter with luke warm heat.

 

[dhcomp]

Glad to hear you got it fixed. I'm late to the part but your situation sounds exactly like what my buddy's Toyota is doing. Been bugging him to fix it for two years now but his wife just drives through winter with luke warm heat.

Lol. Kicking myself for waiting a week....let alone 2 yrs? Thats nuts.

No thanks. I'm about to add seat heaters to mine.....