Cooling question
 

This weekend I replaced most of my cooling system. I put a new radiator, thermostat, water pump and upper and lower hose in my 1985 K10 this weekend. My concern is that my temperature gauge is reading anywhere from 190 to ~ 230 degrees. That seems awful high to me. Is that high and if so, where should I start? I'm wondering if it isn't the thermostat malfunctioning or if it isn't the temperature sending sensor. Any suggestions or comments would be appreciated.

Re: Cooling question
 

That's normal for a small block. Just keep it below 220 or so
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Re: Cooling question
 

I'm going to replace the temperature sensor and if that doesn't work, I'm going to look at the gauges.

Re: Cooling question
 

I don't know what you used for a thermostat, but stock for a lot of these trucks was 195*.
Is it actually overheating, or do you just not like the temp readings?

Engines do need some heat in them. You can run them to cold.

Re: Cooling question
 

I run a 180 degree thermostat in my older vehicles. I drill a 1/8" hole in the thermostat before I install it, it helps keep the pressure equal on both sides and allows the thermostat to open easier.

It is always best to verify the temperature reading before doing anything else unless there are other symptoms.

If you are running a clutch fan make sure it is functioning properly and that the position of the fan is half way inside the shroud.

Re: Cooling question
 

190F sounds a little cold for a fully warmed engine.
I get 200 to 230F cyl head temp.
I get 195 to 205F near T-stat.
OEM gauges have been known to be less than accurate.

Re: Cooling question
 

Seems like mine usually runs ~210.

Re: Cooling question
 

The factory gauges in these trucks can be out of wack too,maybe throw a temp gun at the thermostat housing on both sides to see what the temp actually is.Like shy guy said too,test the thermostat in a pan of water with a meat thermometer also...
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Re: Cooling question
 

The temp is what is worrying me. I did go with the stock temp thermostat.


I'm beginning to suspect that it is my gauge or temp sensor because it is constantly going back and forth and then it will stay at one temp and then go up and down again.

Re: Cooling question
 

I put a 180 degree thermostat in my 83 454 and it stays at a constant 180 or less on the gauge. That is with a stock setup and in 110 degree AZ temps. A fluctuating temp gauge means that the sensor may be faulty - cheap replacement for a guess - I would look for AC Delco or GM sensor if you can find it. Also, it might just be loose wiring - I would check that first. Try to use a digital temp gauge and shoot it at different areas on the engine, especially near the temp sensor.

Re: Cooling question
 

My temp gauge is bouncing back and forth as well. Quite annoying, and I do need to replace the temp sender.

I am running a 195 degree t-stat, and electric fans. Reading the data from my ECM, I see normal temps ranging from 180 cruising at 45 mph, to 225 in stop and go traffic.

Re: Cooling question
 

This thing is killing me. The gauge was fluctuating from around 190 all the way up to 260. I changed the new thermostat for another new thermostat that is supposed to be the best that NAPA sells. I changed the coolant temperature sensor as well. After all was put back together, I started it and watched the gauge. It went right on up to 260 and past it! I shut it down and now I'm here.

What in the heck is going on? Can the gauge in the dash be bad? Could the PO have done something weird with wiring to the coolant temp sensor? Do all small block Chevy coolant sensors run on the same voltage? Can the sensor be messed up? Can I get two bad thermostats in a row? Someone please help me figure this out. I don't want blow this engine up or blow a head gasket....if I haven't already done damage.

Re: Cooling question
 

The top hose is still cool but the temperature gauge is reading 260 degrees.

Re: Cooling question
 

I bought an IR temperature gun and use it all the time to check engine, transmission, differential, bearings, etc.

Makes diagnosing cooling issues much nicer.

Just happened to measure truck temps yesterday:

Left head=208F
Right head = 208
T-Stat house = 210
Rad= 190
oil pan= 195
oil filter= 191
ex manifold= 547
breather=129
carb=139
intake=170F

Re: Cooling question
 

If the upper hose was cool and the gauge climbed (somewhat steadily) to 260, that sounds like something wrong near the thermostat. Did you drill a small hole (.80-.100"?) in the t-stat?

FWIW, my dad's '86 K20 (he bought it new) always read right at 210, and my '85 C3500 did, too, when I got it. After changing the radiator and thermostat in the '85 (I think I replaced it with a 180) it ran right on, or a hair above, the 155 mark, and has ever since. It'll surge to around 170-180 if I've been on the highway and pull off the ramp right into a stop light, but it hardly fluctuates if I'm just driving. And I've driven it close to 40,000 miles since then with no detectable ill effects of it running cooler.

Re: Cooling question
 

Is it that hot and overheating or just "saying" it's that warm? Unless the thermostat is upside down, I'd look toward gauge reading wrong.

When the truck is cold, pop the rad cap off and observe the flow. You can drain about an inch of coolant out of the rad. You can actually see when the thermostat opens. If you can do this with the truck on a hill so the rad is a little higher, you might just have an air bubble that needs to burp out.

Re: Cooling question
 

Running it cooler causes increased wear rate but it will take a while to notice.

Re: Cooling question
 

I've never really trusted electric gauges really myself. Has you tried a mechanical gauge in there to verify actual running temps? The cheap gauges from Equuis are still accurate they just don't last long is all. I would check the dash connections and the gauge and such
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Re: Cooling question
 

Your new coolant temp sensor is putting out the wrong ohm range to go with your guage. They varied over the years as well as from if your truck had warning lights or guages.

Re: Cooling question
 

Can I test the gauge? Where can I get a IR temperature gun?
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Re: Cooling question
 

If you want to cheap out, harbor freight is a place to start. It is a pretty common tool that your parts store may have.

Re: Cooling question
 

Probably the easiest, simplest, and fastest way to correct your issue would be to TEST components before just throwing parts at it. By the sounds of it, I am betting the gauge is bad. You can pick up a real cheap version from nearly any auto parts store. If the mechanical aspects of your cooling system are functioning properly, you should not see temperatures much above what your thermostat is rated at. I wish you the best of luck man.

Re: Cooling question
 

I'm not interested in buying the cheapest one out there. I will pay a little more for something that works. What kind do you have?

Re: Cooling question
 

I got a fairly cheap IR gun at Home Depot. It appears that my gauge or something between my gauge and sensor is not working correctly. I checked all of the temps that Rufton referenced in his post and my temps are fairly close to his. I checked the hell out of my thermostat house and it was anywhere from 198 to 203 regardless of what the gauge said. I feel MUCH better and I sincerely appreciate everyone's help and advice. I'm not sure I would have thought to buy a IR temp gun otherwise. Something about a forest for the tree....

Re: Cooling question
 

That's good news.
I have Raytec and harbor freight; I prefer Raytek.
What brand did you buy at HD and do you like it?