Please tell me I'm ok

[Smokey burnouts]

Got this K5 about a month ago and I guess like everybody else I'm slowly messing with things getting the little things fixed and back working. In doing this I realize the wire on the sending unit for the coolant had a bad connection and was causing my gauge not to read. Now that it's fixed it is showing that the truck is running hot, way hot. I have tried an advanced auto parts radiator thinking that maybe mine was busted (which it does have a small leak at the top of the tank). Well that radiator got really hot really quick so now I'm back to the original four row all brass radiator and it's still reading hot.

I'm hoping that since I've been driving the truck for a month with 60+ mile trips in 85-95° weather and it's never actually what I would consider overheated and steam blowing out of the radiator. Maybe it's one of the sending units with the wrong resistance and the gauges reading inaccurate?? Ideas??

Think I'm picking up an infrared heat gun tomorrow and going to try to get a reading off the thermostat housing or the hot side of the radiator and see what I get.

Thanks
Daniel

[pound41]

check both sides of the block you might find another temp sensor

[bamachem]

Did you replace/check the thermostat before you swapped radiators? It may be stuck or corroded and impeeding flow. Could also be a bad water pump and it's not putting out enough flow.

[Smokey burnouts]

Originally Posted by bamachem

Did you replace/check the thermostat before you swapped radiators? It may be stuck or corroded and impeeding flow. Could also be a bad water pump and it's not putting out enough flow.

Yeah I checked it and it opens and closes. I just put in a new one that's 180* where old one was 195.

When I hit engine with IR thermometer the corner of the rad tank(where the engine coolant enters) I was reading about 196*, at the manifold right below chrome thermostat housing reading about 185*, but now if I shot the temp sending unit(manifold mounted) or right below it was reading 215-220*

[truckster]

OK, this may sound like a simplistic question, but when you start the truck, does the temp gauge gradually move to hot, or is it there right away?

If it's gradually moving, I'd echo what others have said and replace the thermostat.

If it's reading hot as soon as you turn on the ignition, you've grounded the wire to the gauge.

As far as being OK, Chevy small blocks are generally pretty forgiving. Just don't do what my father-in-law did and put a hose in the radiator when the engine is overheated.

[mtully79]

Check your water pump as well. If it's not pushing enough flow you will run hot.

[87Skier]

It could also be the wrong sending unit. They have varying resistances.

Verify with a heat gun or something else to ensure that it is actually running hot. I once watched a guy working on his Ford spend about 8 hours working on it thinking it was overheating, replaced a ton of parts, only to find out the sending unit went bad.

[Smokey burnouts]

Originally Posted by mtully79

Check your water pump as well. If it's not pushing enough flow you will run hot.

I am noticing that it will climb in temps when I'm coasting, ideling or generally low RPMs but when I get on the throttle the temp will drop..... To me that sounded like could be a weak water pump.....???

[bamachem]

Sounds like it to me. Could also be poor radiator flow (plugged) and when you increase RPM, you increase fan speed, drawing more air over the fins. Could be either. The water pump is less than $30 and only takes a few minutes to change out. Not so lucky with the radiator, but you should be able to look into the radiator to see if there's a lot of scaling and buildup inside.

[Smokey burnouts]

Originally Posted by bamachem

Sounds like it to me. Could also be poor radiator flow (plugged) and when you increase RPM, you increase fan speed, drawing more air over the fins. Could be either. The water pump is less than $30 and only takes a few minutes to change out. Not so lucky with the radiator, but you should be able to look into the radiator to see if there's a lot of scaling and buildup inside.

It looks pretty good in there also decent flow coming through the top rows/channels that are above the coolant level

[mtully79]

I had similar problems, I went with a 3 core aluminum radiator and stewart phase II pump. I added (2) 14" electric fans as well, might be overkill but I sometimes sit in a lot of beach traffic in the summertime and the fans make a big difference.

Good luck with the diagnosis, sounds like you are on the right track and have some great minds on the forum to help you along the way.

[mtully79]

Originally Posted by Smokey burnouts

I am noticing that it will climb in temps when I'm coasting, ideling or generally low RPMs but when I get on the throttle the temp will drop..... To me that sounded like could be a weak water pump.....???

Don't forget increased air flow over the coils can drop temp when you're moving.

[viking427]

IR gun is a the right tool. Doesnt sound like exhaust gasses are making their way into the coolant circuit - usually you cant keep coolant in the radiator when that happens, unless its a very small leak. Might be running lean - check carb jetting and timing.

[franken]

Does it have a fan shroud? It should, and the fan blades should be about half in the shroud.
You might replace the belts since there may be slipping and chances are they need it.

[sawman]

sounds like you belt is lose,when you throttle up belt tightens up,

[BobbyK]

Originally Posted by franken

Does it have a fan shroud? It should, and the fan blades should be about half in the shroud.
You might replace the belts since there may be slipping and chances are they need it.

Fan shroud will make a BIG difference...especially at low speed.

[Smokey burnouts]

Originally Posted by BobbyK

Fan shroud will make a BIG difference...especially at low speed.

It has a shroud.... Think I got the temp good to go now, all new coolant and a 180 thermostat. So far it's hoding up fine. Thanks for all the help

[asolde]

What did you do to fix it?

[Smokey burnouts]

Originally Posted by asolde

What did you do to fix it?

Think putting the lower thermostat helped the most, still think it's gets hotter than it should but then drops and stays pretty decent

[bp71k5]

I don't think 195 is very hot. That's stock operating temp for the later model V8. I run mine at 195-210 with electric fans and fuel with fuel injection. Its probably just fine.