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Old 12-06-2017, 12:04 AM   #26
hillbillyrider
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Re: truck wont warm up

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Originally Posted by TennesseeZ View Post
Sounds like the problem is that engine not getting up to operating temp. I'd try old school investigation to find what's causing that problem. first use a thermometer in the radiator to confirm that the guage is showing the actual engine temp. Then I'd bypass the heater core by removing both hoses from it and hooking them to each other with tubing and hose clamps. Run the engine at varying speeds for 15 min. If that doesn't do anything remove the return hose at the radiator, plug the nipple on the radiator with a short piece of tubing and a bolt or something to plug it. Put a water hose with a rag around it in the radiator fill neck and run it some more. If no change make sure the spark plugs are the right ones. Maybe block off the thermostat itself by wrapping it with tinfoil and reinstalling.

I had one once that did the same exact thing you describe, I was working 7/12s (out of town in Minnesota in February) and couldn't work on it. On the way to the mechanic's shop it magically healed itself. Turns out it had an air pocket in the cooling system, once that got out it worked fine for the rest of the time I owned it, about 6 yrs. Don't know how to get it out, just time and driving I guess, maybe the hose in the fill neck would do it. Hope some of his helps.
Thanks. that is exactly what I have been saying. the engine is not getting up to operating temp. i should not be able to stick my finger in the coolant after 45 minutes of run time without it burning me. It acts as if there is no thermostat in it. There have been two put in and of the correct size. i may try the blocking off of it and see what happens. gonna flush the whole system first though. thanks again.
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Old 12-06-2017, 01:03 AM   #27
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Re: truck wont warm up

I still don't understand the hose coming off the radiator that is cut and plugged? Doesn't it go to the heater core? That cut / plug isn't factory. The plumbing is suspect to me.




I took the dying 350 out of my 94 GMC Sierra 1/2 ton and dropped in a 454. I initially bypassed the heater core due to not having hose on hand during the swap. I just hooked it up a few weeks ago and used that port you have cut and plugged to go to the heater core. I have hot heat and my aftermarket temp guage shows I get up to temp. Different engine, but I still think that hose needs hooked up

Last edited by Sixball; 12-06-2017 at 01:11 AM.
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Old 12-06-2017, 02:44 AM   #28
hillbillyrider
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Re: truck wont warm up

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I still don't understand the hose coming off the radiator that is cut and plugged? Doesn't it go to the heater core? That cut / plug isn't factory. The plumbing is suspect to me.




I took the dying 350 out of my 94 GMC Sierra 1/2 ton and dropped in a 454. I initially bypassed the heater core due to not having hose on hand during the swap. I just hooked it up a few weeks ago and used that port you have cut and plugged to go to the heater core. I have hot heat and my aftermarket temp guage shows I get up to temp. Different engine, but I still think that hose needs hooked up
yes. according to youtube vids that plugged hose on the radiator goes to the heater core. they have the hose from the core running to the water pump. i am going to switch it tomorrow. I doubt it will have any effect on the engine temp though.
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Old 12-06-2017, 11:11 AM   #29
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Re: truck wont warm up

Whether the hose goes to the water pump or to the rad, it's still just the return line. The pressure line to the core is the one from the intake.

So one more question.
When you pop the rad cap off when the motor is cold, where is the coolant level?
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Old 12-06-2017, 11:29 AM   #30
hillbillyrider
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Re: truck wont warm up

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Whether the hose goes to the water pump or to the rad, it's still just the return line. The pressure line to the core is the one from the intake.

So one more question.
When you pop the rad cap off when the motor is cold, where is the coolant level?
right at the bottom of the neck.
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Old 12-06-2017, 12:15 PM   #31
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Re: truck wont warm up

Level should be right at where the rad cap seal is.
Is your recovery tank working like normal?
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Old 12-06-2017, 01:29 PM   #32
hillbillyrider
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Re: truck wont warm up

now that i don't know
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Old 12-06-2017, 01:39 PM   #33
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Re: truck wont warm up

The recovery tank should have a cold setting mark on it for the level. The hose off the rad should always be submerged in that coolant level. You don't want the hose to ever draw air back into the rad.
THere will also be a high level mark on the tank. That's where the coolant should be when the motor is hot.
If you're pulling in air all the time you'll get air pockets in the system. You won't get heat from the air pockets.
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Old 12-06-2017, 01:41 PM   #34
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Re: truck wont warm up

roger that. will double check before and after i flush the system. thanks
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Old 12-06-2017, 05:14 PM   #35
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Re: truck wont warm up

ok so i back flushed the heater core and it was really clean. I didn't mess with flushing the rest of the system. no sign of stop leak or bad corrosion. the recovery tank seems to be working fine. I am going to NAPA to get a T-stat. the one from advance auto may just be a pile of crap. will update tomorrow on how it goes.
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Old 12-07-2017, 07:58 AM   #36
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Re: truck wont warm up

Once running for awhile, you say the top hose is warm, but what about the engine? If that is hot, I’d say t-stat, also if same temp as hose. POS t-stat lol.
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Old 12-08-2017, 04:21 PM   #37
hillbillyrider
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Re: truck wont warm up

i have been on this pos all friggin day. put the best t-stat that napa had in. 195*. top radiator hos is the only hose that will get hot. neither heater hose or bottom radiator hos will get hot. just BARELY warm. According to temp gauge it is only reaching roughly 120*. heat is just barely warm. another thing i noticed is the right side of the radiator get as hot as the top hose (same side as top hose). left side is just warm.
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Old 12-08-2017, 07:08 PM   #38
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Re: truck wont warm up

drained the whole system and filled it with white distilled vinegar. run it for 15 minutes. letting it sit now and will drain and refill with coolant in about 3 hours. i hope it works. lol
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Old 12-08-2017, 07:30 PM   #39
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Re: truck wont warm up

What kind of fan you got?
Is your a/c compressor wiring correct?
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Old 12-08-2017, 07:32 PM   #40
hillbillyrider
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Re: truck wont warm up

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What kind of fan you got?
Is your a/c compressor wiring correct?
it has the clutch fan. no electric fans and the a/c dont work.
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Old 12-08-2017, 07:41 PM   #41
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Re: truck wont warm up

The a/c not working might be the problem. With it not working maybe there's a door(flap) open that shouldn't be. Letting in cold air to the fan.
Reason I say that is if I unplug my compressor I don't get much heat from my heater either.
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Old 12-08-2017, 08:00 PM   #42
hillbillyrider
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Re: truck wont warm up

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Originally Posted by geezer#99 View Post
The a/c not working might be the problem. With it not working maybe there's a door(flap) open that shouldn't be. Letting in cold air to the fan.
Reason I say that is if I unplug my compressor I don't get much heat from my heater either.
the problem isn't the heat. the problem is the engine will not warm up. the temp coming from the heater is consistent with the temp of the engine. I have even blocked off part of the radiator and the temp only increased by about 10 degrees.
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Old 12-08-2017, 09:32 PM   #43
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Re: truck wont warm up

Block off the whole rad except for a 6 inch hole in the center.
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Old 12-10-2017, 06:39 PM   #44
hillbillyrider
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Re: truck wont warm up

Update. Git it fixed. There was an air pocket that was tough to get out. finally got it out by letting it idle for about 2 hours blipping the throttle occasionally and pumping the top rad hose. temp is normal now. still had no heat and found the intake line to the heater core was almost completely plugged. all cleaned out and good heat now. thanks for all the help.
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Old 12-12-2017, 09:31 AM   #45
arrg
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Re: truck wont warm up

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Looks like you have the hoses set up like a 60's to 70's heater hose set-up, but these systems don't work that way anymore. You've got two "pressure" connections and no return. The connection on top of the water pump should be plugged and routed to the fitting under the radiator cap. That's your return line; from the firewall to the radiator. Have you blasted out your heater core?
Agree with this 100%. The return line should run from the heater core to the radiator on the TBI trucks. The top of the water pump should have a plug in it. Also, that rear coolant port on the intake manifold should have a metal restrictor in the gasket. If that's not in there it can cause problems too.
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