overheating update - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ocbaud · 01-30-2005, 02:22 PM

okay, yesterday i had my dads new radiator cap on and i changed the tstat to a 160 model and also drilled 2 small holes in it, in case there is any air pockets that need out. MOST of the time it will run really cool. the heater works well, but not as warm as it was before with the 180 tstat.
every once in awhile(either on the highway, geting off the highway, on the street doing 50 or 5) it will steadly go up to 260degrees. when its that hot, the heater is still blowing the same amount of heat as it was when it was running at normal temp. after maybe 5 to 10 or so seconds, it will QUICKLY drop back down to operating temp. i would say it takes about 2 secs max for it to go from 260 back down to 160 or so. after i got home, the overflow tank didnt have any more coolant in it than normally. i never smelled antifreeze and it just didnt act like it was really overheating.

could a faulty sender cause this?

SCOTI · 01-30-2005, 02:31 PM

Get a freaking mechanical temp gauge & end this misery please. Just hook it up under the hood & keep the gauge on your seat/dash while driving around & see what your temps read.

hotrodhomi · 01-30-2005, 02:33 PM

that would be a cheap troubleshooting tool but I wouldnt leave it in there.

eagle23 · 01-30-2005, 09:52 PM

It does sound like the sensor or the gauge itself may be bad. That the heater output temp didn't change really does point to the readings, but not the reality. The temp sensor is all of $20 at Rock Auto for one that goes with a gauge. That's pretty cheap to test and just take a chance.

As some one mentioned earler, your water pump may be a co-conspirator, since you said it's making odd sounds.

You're getting closer, though. You may yet be able to put that 180 deg t-stat back and give your dad back his radiator cap

Brian

**Boog** · 01-30-2005, 11:14 PM

It's good to know your engine is not overheating afterall.
This is just like my 85 did. It's gauge reading would go up to extreme hot reading sitting idling in my shop in 30* temp 3 minutes after startup. I knew the engine wasn't really overheating so I replaced the gauge sending unit with a GM part. No change. This started after I replaced the stat with a 195. Never happend before. I even bought a new GM gauge and no change. Inspected all the grounds and wires all the way to the temp sender. I put the 165* stat back in and it registered correctly again. Wish I'd kept that one long enough to nail the cause.
You can put an aftermarket mechanical gauge in there to verify the temps are running normal and buy yourself some time to try figuring this one out.

Prerunner1982 · 01-30-2005, 11:19 PM

yes definately get another temp guage... oh.. and give me back my multimeter now that you got it figured out...lol

ocbaud · 01-31-2005, 12:34 AM

i got my own multimeter jon

i've also borrowed a friends autometer temp gauge to wire up and check to see

i've got the wire for the guage running right alongside the plug wires

**Boog** · 01-31-2005, 01:16 AM

I even pulled the gauge cluster out of the dash and started the engine to see if there was a naked spot on a wire or something back there causing the gauge to go hot but found nothing. I examined the printed circuit and found nothing. Since yours doesn't do it right off the bat after starting it is a bit different than mine was. The only thing I didn't do when checking mine was to take the fuse panel apart to look behind it for a naked wire spot.

Prerunner1982 · 01-31-2005, 12:53 PM

Quote:

Originally Posted by ocbaud

i got my own multimeter jon

thats funny.... cant seem to find mine....

01-30-2005, 02:22 PM	#1
ocbaud Garage Queen Material Join Date: Oct 2002 Location: USA Posts: 4,129	overheating update okay, yesterday i had my dads new radiator cap on and i changed the tstat to a 160 model and also drilled 2 small holes in it, in case there is any air pockets that need out. MOST of the time it will run really cool. the heater works well, but not as warm as it was before with the 180 tstat. every once in awhile(either on the highway, geting off the highway, on the street doing 50 or 5) it will steadly go up to 260degrees. when its that hot, the heater is still blowing the same amount of heat as it was when it was running at normal temp. after maybe 5 to 10 or so seconds, it will QUICKLY drop back down to operating temp. i would say it takes about 2 secs max for it to go from 260 back down to 160 or so. after i got home, the overflow tank didnt have any more coolant in it than normally. i never smelled antifreeze and it just didnt act like it was really overheating. could a faulty sender cause this?

01-30-2005, 02:31 PM	#2
SCOTI Registered User Join Date: Apr 2001 Location: DALLAS,TX Posts: 22,064	Get a freaking mechanical temp gauge & end this misery please. Just hook it up under the hood & keep the gauge on your seat/dash while driving around & see what your temps read. __________________ 67SWB-B.B.RetroRod 64SWB-Recycle 89CCDually-Driver/Tow Truck 99CCSWB Driver All Fleetsides @rattlecankustoms in IG Building a small, high rpm engine with the perfect bore, stroke and rod ratio is very impressive. It's like a highly skilled Morrocan sword fighter with a Damascus Steel Scimitar..... *Cubic inches is like Indiana Jones with a cheap pistol.*

01-30-2005, 11:14 PM	#5
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,514	It's good to know your engine is not overheating afterall. This is just like my 85 did. It's gauge reading would go up to extreme hot reading sitting idling in my shop in 30* temp 3 minutes after startup. I knew the engine wasn't really overheating so I replaced the gauge sending unit with a GM part. No change. This started after I replaced the stat with a 195. Never happend before. I even bought a new GM gauge and no change. Inspected all the grounds and wires all the way to the temp sender. I put the 165* stat back in and it registered correctly again. Wish I'd kept that one long enough to nail the cause. You can put an aftermarket mechanical gauge in there to verify the temps are running normal and buy yourself some time to try figuring this one out. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross Last edited by Boog; 01-30-2005 at 11:17 PM.

01-31-2005, 01:16 AM	#8
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,514	I even pulled the gauge cluster out of the dash and started the engine to see if there was a naked spot on a wire or something back there causing the gauge to go hot but found nothing. I examined the printed circuit and found nothing. Since yours doesn't do it right off the bat after starting it is a bit different than mine was. The only thing I didn't do when checking mine was to take the fuse panel apart to look behind it for a naked wire spot. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

01-30-2005, 02:33 PM	#3
hotrodhomi Registered User Join Date: Apr 2004 Location: Sacramento Posts: 3,737	that would be a cheap troubleshooting tool but I wouldnt leave it in there.

01-30-2005, 09:52 PM	#4
eagle23 Active Member Join Date: Feb 2004 Location: Atlanta GA Posts: 174	It does sound like the sensor or the gauge itself may be bad. That the heater output temp didn't change really does point to the readings, but not the reality. The temp sensor is all of $20 at Rock Auto for one that goes with a gauge. That's pretty cheap to test and just take a chance. As some one mentioned earler, your water pump may be a co-conspirator, since you said it's making odd sounds. You're getting closer, though. You may yet be able to put that 180 deg t-stat back and give your dad back his radiator cap Brian

01-30-2005, 11:19 PM	#6
Prerunner1982 Registered User Join Date: Oct 2002 Location: Edmond, OK Posts: 5,904	yes definately get another temp guage... oh.. and give me back my multimeter now that you got it figured out...lol

01-31-2005, 12:34 AM	#7
ocbaud Garage Queen Material Join Date: Oct 2002 Location: USA Posts: 4,129	i got my own multimeter jon i've also borrowed a friends autometer temp gauge to wire up and check to see i've got the wire for the guage running right alongside the plug wires



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