Overheating Only Under Load

[Zed Head]

So you can sit in the garage and let it rev at 3000 and no heat increase?

Just trying to add something.  The more words the better.  Good luck.

[w3wilkes]

On 8/14/2022 at 11:23 AM, Zed Head said:

So you can sit in the garage and let it rev at 3000 and no heat increase?

Just trying to add something.  The more words the better.  Good luck.

What I saw towards the end of the video was the temp gauge pegged and then rev the engine to ~3000RPM and the temp gauge came back down under no load. I thought you or someone suggested trying a new temp sending unit to see if that's where the problem lies. It would be interesting to see what an IR temp sensor would show on the t-stat housing when the temp gauge is pegged.

[DadAndLadZ]

1 minute ago, w3wilkes said:

It would be interesting to see what an IR temp sensor would show on the t-stat housing when the temp gauge is pegged.

I thought so too but don’t have access to one. Just picked up a replacement temp sender today and will be installing it ASAP. Will report back!

[Zed Head]

I'm going to guess that the water pump is not pumping or is pumping at a low rate.  Maybe there's a blockage.  The hot coolant is just moving slowly by the sender right after it picks up the extra heat from the "load test".  In the garage with no load, the extra RPM move the coolant just a little bit faster pulling cooled coolant through from the radiator.

The gauge needle behavior looked normal, plus it started from the correct spot for an idling warmed up engine.  The proposal of a bad sender really just means that it's correct at about 180, but shoots up ~10 degrees / real degree after 180.

It might be scary to do but if you load tested at higher RPM you might get a different result.  Keep the revs up to keep the coolant moving.

Just trying to fit the puzzle pieces together.  When you dump the flushing chemicals you might remove the top radiator hose and see what kind of flow you have.  Don't drain it, use the engine and water pump to push it out.  Another data point...

 

Edited August 15, 2022 by Zed Head

[DadAndLadZ]

7 minutes ago, Zed Head said:

I'm going to guess that the water pump is not pumping or is pumping at a low rate.  …  Another data point...

 

Thanks for all that, points to ponder!

[Zed Head]

p.s. what's up with your oil pressure gauge?  Disconnected at the engine?

[DadAndLadZ]

Just now, Zed Head said:

p.s. what's up with your oil pressure gauge?  Disconnected at the engine?

Haven’t gotten around to it yet. On the list. Just now got the carbs sorted so it will run steady.  

[DadAndLadZ]

Well we put in a new sender today but now it just goes to max and doesn't come back down. lol... We were just starting to goof around with it when we nearly ran the car out of gas in the driveway, so will have to get back to it tomorrow.

[Captain Obvious]

8 hours ago, DadAndLadZ said:

Well we put in a new sender today but now it just goes to max and doesn't come back down.

Yeah, you'll need to spend some time on that. Glad I helped you make it "better"?  LOL!  

First thing I would do now is pull the wire off the new sender when the gauge is at max and see what happens. It SHOULD drop to low temp. If it doesn't, then there's a problem in the wiring or inside the gauge itself.

[DadAndLadZ]

43 minutes ago, Captain Obvious said:

First thing I would do now is pull the wire off the new sender when the gauge is at max and see what happens. It SHOULD drop to low temp.

Hey, good tip, thanks!