Author Topic: Cooling Issue  (Read 115 times)

Offline Dirtboy

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Cooling Issue
« on: January 13, 2020, 08:15:27 AM »
85 K20
Newly remanfactured ATK crate 350, 87 up block, pre 86 heads
Whatever cam they used, assume stock
Chevrolet dual plane aluminum manifold
New Edelbrock 1406 Carb with fuel pressure regulator and new filter
Fresh rodding and rebuild of the radiator
New T-stat., Edelbrock 160 degree with 1/8th inch hole drilled in it
New water pump and new top/bottom rad hoses
New temperature sending unit (mounted in the side of the block near the head, stock location)
New temp gauge (stock reproduction, in-dash unit)

Here's the issue, the truck heats up at idle to just under 210 (center of the gauge) and stays right around there under light driving (heats up by a degree or two). When I get out on the highway and drive it at 65 mph (3000 RPM) it heats up to 217ish - 220, when I come to a light or stop, it will immediately start to cool back down to 210. I drove it and heated it up to 217ish, and then stopped and quickly checked the thermostat housing with an infrared temp gun and it reads 168 degrees while the gauge reads 217. The truck then dropped back down to 210. Truck doesn't overheat, the upper and lower radiator hoses are cool enough to hold on to and you can hold your hand on the radiator cap.

Infrared temp gun was checked against a pot of boiling water and it read 211.
Old temperature gauge read the same way as the new one so it's not the gauge.

I do not have any info from ATK engines on how much, if any, the cylinders were bored out, but I do know that sometimes a bored, remaned engine can run a little warmer since the cylinder walls are thinner so there's that. I am assuming that the engine was bored out at least .30 over.

Any ideas?

Offline Irish_Alley

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Re: Cooling Issue
« Reply #1 on: January 13, 2020, 08:49:17 AM »
With a 160 thermostat you shouldn't see temps that high.
What type of fan do you have is the shroud in place?
What type of belt system do you have? Could you have a reverse rotation pump?
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

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Offline Dirtboy

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Re: Cooling Issue
« Reply #2 on: January 13, 2020, 08:59:04 AM »
Original 5 blade fan with a new hydrostatic clutch and yes the shroud is in place. Original pulleys and belts that were on the truck when I bought it six years ago. As far as the pump, its pumping the correct way. It draws down the right side of the radiator and coolant flows from left to right through the core. (I did top it off after drawing down when I replaced the pump.)
« Last Edit: January 13, 2020, 09:19:43 AM by Dirtboy »

Online bd

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Re: Cooling Issue
« Reply #3 on: January 13, 2020, 09:26:50 AM »
Sounds like a faulty or incorrect temp sensor.  Drop a manual thermometer into the radiator neck and compare its reading to the gauge.  Substitute a known resistance for the sender and see how the gauge responds; use "Functional Tests of Factory GM Electric Gauges" for reference.
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In other words... if people learn by making mistakes, by now I should know just about everything!!!
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Offline Irish_Alley

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Re: Cooling Issue
« Reply #4 on: January 13, 2020, 12:06:30 PM »
A reverse rotation pump won't pump in the wrong direction as the belts will still turn the pump in the right direction. It just won't pump the water as efficient as it's supposed to. But I must admit I missed the part about the temp on the thermostat housing.

I'm leaning with bd, if the temp was really 200+ you shouldn't be able to hold the hoses comfortably. When did you replace the temp sending unit?
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline Dirtboy

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Re: Cooling Issue
« Reply #5 on: January 13, 2020, 01:11:57 PM »
True that on the reverse pump, but if you order a new, not re-manufactured pump for an 85 Chevy 350, it shouldn't be a reverse flow... those didn't come along until the 90's right? I replaced the sending unit when I installed the remaned engine.

Offline VileZambonie

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Re: Cooling Issue
« Reply #6 on: January 13, 2020, 03:36:15 PM »
Reverse rotation is serpentine belt driven and the pulleys do not interchange. Get a temperature reading thermocap for the radiator. I agree, sounds like wrong sending unit/gauge combo. The sending unit should be threaded into the cylinder head not the cylinder block.
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Offline Dirtboy

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Re: Cooling Issue
« Reply #7 on: January 15, 2020, 09:49:29 AM »
Swapped out the temperature sending unit last night with a higher quality Standard brand and now the gauge is reading 155 degrees and the thermostat housing is reading 148 to 150. I think that's fairly accurate. Thanks for the help.