Heat temp gun/correct temp sensor/etc.

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ChuckN

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I’ve been taking out the truck for some drives lately instead of wrenching, since the weather is turning good.

The old temp sensor was bad, so I picked up a duralast sensor that was supposed to be correct. Well, it’s likely off. I have a 160 thermostat, and it sits stable at just under 210 and doesn’t waver, so I’m guessing the ohms are off for what it needs to read right.

What do you guys check with, or do you have a recommendation as to check accuracy?

It was a 250 I6 truck originally with A/C but has a 355 in it now with some sort of a lumpy cam, and camelhump heads. I didn’t build it, but it is freshly rebuilt with a new water pump and when at 60 mph it’ll creep up to 220 on the gauge when it’s 70 degrees outside- which I suspect is lower than that. I need to measure the actual core size of the radiator, will post that later. The guy before me that owned it, well, I don’t consider him an accurate source of information but not dishonest.

Timing is set to 35 deg of advance at 3500.

It seems happier when cruising around town- heat rises when consistently at highway speeds, and then cools down when back in town, making me think that the radiator won’t keep up when real summer temperatures hit.

Open to any and all suggestions, except for electric fans. I’m stupid, so I’m keeping it simple as they say.
 

1STLS1

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The fact it gets warm on the highway suggests it's a flow issue in the radiator or it's too small of a radiator. Also verify the cap is functioning and not bleeding off pressure. Rock Auto has all the sizes listed in their on line catalog for all the engines offered so you should be able to determine if the size is an actual factor.

Is the radiator copper/brass or aluminum and plastic? Older copper /brass ones plug up and may require "rodding" where they remove a side tank, run flat steel rods thru the core then resolder it back together or, the more cost effective repair in todays world, replacement with a aluminum cored radiator.
 

ChuckN

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The fact it gets warm on the highway suggests it's a flow issue in the radiator or it's too small of a radiator. Also verify the cap is functioning and not bleeding off pressure. Rock Auto has all the sizes listed in their on line catalog for all the engines offered so you should be able to determine if the size is an actual factor.

Is the radiator copper/brass or aluminum and plastic? Older copper /brass ones plug up and may require "rodding" where they remove a side tank, run flat steel rods thru the core then resolder it back together or, the more cost effective repair in todays world, replacement with a aluminum cored radiator.
Thanks for your reply- cap is brand new. I measured the core (not including the side tanks) and it looks to be about 28 1/2” wide, and about 17” or so tall. Depth looks to be around 1” so I don’t know how many rows that would be.

Kind of bummed- there used to be a radiator shop here in town that rebuilt them with new cores and did a great job. But, they closed down. Too bad because they did a great job with rebuilding my 3100 radiator with a new core while using the original tanks with the ‘54 stamp on them.
 

fast 99

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If sensor is in the head temperature it will be 10-15 degrees hotter than the thermostat, possibly even more than that. Reason I know this is because I had a mechanical gauge in the head on one vehicle. Using a temp gun verified it. It was always hotter. With a 190-degree stat, head ran in the 210 area.

Personally, if it isn't pushing water out or thumping after hot shut off, its probably ok.
 

ChuckN

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If sensor is in the head temperature it will be 10-15 degrees hotter than the thermostat, possibly even more than that. Reason I know this is because I had a mechanical gauge in the head on one vehicle. Using a temp gun verified it. It was always hotter. With a 190-degree stat, head ran in the 210 area.

Personally, if it isn't pushing water out or thumping after hot shut off, its probably ok.
Thanks for posting! As it is, the sensor is in the thermostat housing in the intake manifold.
 

Albrigap

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Buy the sender for the 250 I6.
The sender should match the truck and not the engine.
 

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