Cooling system gremlin - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Notes · 07-17-2020, 10:30 PM

72 C10 with 350. Put everything back together after installing AC. Drove about 50 miles with no problems. Drove 20 miles today, parked truck for a few hours, then started it up. Within 2 miles the factory temp gauge pegged. Put in 1/2 gallon of water/ant-freeze. Drove 20 miles home at 70 mph with no problems. Let it idle in the driveway for 10 minutes with the AC running & temps stayed fine. Radiator is still full. Where did the coolant go & why did it overheat so fast? Kinda gun-shy to drive it now. Time for an overflow reservoir?

gmc684x4 · 07-17-2020, 10:37 PM

Did you check your oil for antifreeze

Did you pressure test your coolant system ?

Did you top up the coolant after changing it for the ac setup ?

**Steeveedee** · 07-17-2020, 11:26 PM

It was probably just not entirely full, and then burped. Keep an eye on it for leaks.

**Stocker** · 07-18-2020, 08:50 AM

Quote:

Originally Posted by Notes

Time for an overflow reservoir?

An overflow reservoir is always a good idea IMHO. Inexpensive, easy to do, no more coolant loss (assuming a good cooling system), radiator is always full. No downside to this mod, unless you just have to keep your truck 100% showroom stock. Remember to use a radiator cap for a sealed system.

Notes · 07-18-2020, 10:22 AM

Oil is fine. No smell or sweet taste to condensation out of tailpipe. No bubbles in coolant with radiator cap removed. Also with cap removed, when it warms up the fluid "surges" out of the small overflow pipe on the radiator. That stops when cap is replaced. No room to mount overflow reservoir on passenger side. The bracket for the windshield wiper fluid is still there on the drivers side. Could I use a replacement tank for that as the radiator reservoir with the hose routed under the fan shroud? Would also get the proper radiator cap. 15lbs.? Hope it just needed to burp. I do that occasionally. Then my wife over-heats. Thanks for the help.

hjewell2 · 07-18-2020, 11:20 AM

Quote:

Originally Posted by steeveedee

it was probably just not entirely full, and then burped. Keep an eye on it for leaks.

bingo

**Stocker** · 07-18-2020, 12:06 PM

Quote:

Originally Posted by Notes

The bracket for the windshield wiper fluid is still there on the drivers side. Could I use a replacement tank for that as the radiator reservoir with the hose routed under the fan shroud? Would also get the proper radiator cap. 15lbs.?

Yes and Yes. My tank is mounted on the drivers side of the core support and the hose is under the shroud. Was like that when I bought the truck in 1977.

Notes · 07-18-2020, 12:41 PM

Great. That's what I'll do. One more: Do I want a cap with or without the pressure relief lever on top?

**Stocker** · 07-18-2020, 01:36 PM

That *may* be just personal preference..... I'm not really sure. I've seen those but never owned one, so in this case at least, the lever is not required.
I have a feeling the lever makes it a bit safer to release pressure when the coolant is hot. You're maybe less likely to get scalded.

**Steeveedee** · 07-18-2020, 01:38 PM

I personally prefer the lever type. I had a customer come in one time with an overheating engine, and I went to loosen the cap after running water on it. It turned out to be almost off, and the small amount of turning I did let the cap all the way off. Hot coolant shot all over my face. I quickly turned the hose on my face to take the heat away. Not even a blister. I was really lucky not to have been blinded.

garyd1961 · 07-18-2020, 06:02 PM

Before I got a real overflow bottle I just used a jug with a hole in the top. I placed it in the hole down by the horns and used a long overflow hose to reach. You need the right cap also.

custom10nut · 07-19-2020, 08:18 AM

My gremlin is with the “Gauge Reading“(Original 70 in W/gage dash panel). I have an issue with the needle on the gauge making a steady climb until it pegs on the right side, of course this SHOWS overheated. I just went through and Put in a new sending unit, t-stat, and Water pump, and still the gauge does the same. After replacing everything I filled it back up, and let it burp all the air bubbles out, then I used a thermometer at the radiator cap the check the temp, and it stays right around 155 degrees. After the T-stat opens I can watch the coolant flowing so I know I’m getting circulation,
I’ve read that Auto Wire has a sending unit made to original specs for the Gen 1 engines (prior to 1978, according to their site).
I want to fix this issue, but I’m getting tired of buying new parts, thinking it fix it, only to find I still have the problem.
Has anyone else used this AUTO WIRE sending unit, and did it work?

07-17-2020, 10:30 PM	#1
Notes Registered User Join Date: Sep 2017 Location: Center Point, Iowa Posts: 82	Cooling system gremlin 72 C10 with 350. Put everything back together after installing AC. Drove about 50 miles with no problems. Drove 20 miles today, parked truck for a few hours, then started it up. Within 2 miles the factory temp gauge pegged. Put in 1/2 gallon of water/ant-freeze. Drove 20 miles home at 70 mph with no problems. Let it idle in the driveway for 10 minutes with the AC running & temps stayed fine. Radiator is still full. Where did the coolant go & why did it overheat so fast? Kinda gun-shy to drive it now. Time for an overflow reservoir?

07-17-2020, 10:37 PM	#2
gmc684x4 Registered User Join Date: Jul 2012 Location: Whitehorse yukon Posts: 1,218	Re: Cooling system gremlin Did you check your oil for antifreeze Did you pressure test your coolant system ? Did you top up the coolant after changing it for the ac setup ?

07-17-2020, 11:26 PM	#3
Steeveedee Who Changed This? Join Date: Jan 2013 Location: Simi Valley, CA Posts: 10,324	Re: Cooling system gremlin It was probably just not entirely full, and then burped. Keep an eye on it for leaks. __________________ ~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA

07-18-2020, 10:22 AM	#5
Notes Registered User Join Date: Sep 2017 Location: Center Point, Iowa Posts: 82	Re: Cooling system gremlin Oil is fine. No smell or sweet taste to condensation out of tailpipe. No bubbles in coolant with radiator cap removed. Also with cap removed, when it warms up the fluid "surges" out of the small overflow pipe on the radiator. That stops when cap is replaced. No room to mount overflow reservoir on passenger side. The bracket for the windshield wiper fluid is still there on the drivers side. Could I use a replacement tank for that as the radiator reservoir with the hose routed under the fan shroud? Would also get the proper radiator cap. 15lbs.? Hope it just needed to burp. I do that occasionally. Then my wife over-heats. Thanks for the help.

07-18-2020, 12:41 PM	#8
Notes Registered User Join Date: Sep 2017 Location: Center Point, Iowa Posts: 82	Re: Cooling system gremlin Great. That's what I'll do. One more: Do I want a cap with or without the pressure relief lever on top?

07-18-2020, 01:36 PM	#9
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,586	Re: Cooling system gremlin That may be just personal preference..... I'm not really sure. I've seen those but never owned one, so in this case at least, the lever is not required. I have a feeling the lever makes it a bit safer to release pressure when the coolant is hot. You're maybe less likely to get scalded. __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

07-18-2020, 01:38 PM	#10
Steeveedee Who Changed This? Join Date: Jan 2013 Location: Simi Valley, CA Posts: 10,324	Re: Cooling system gremlin I personally prefer the lever type. I had a customer come in one time with an overheating engine, and I went to loosen the cap after running water on it. It turned out to be almost off, and the small amount of turning I did let the cap all the way off. Hot coolant shot all over my face. I quickly turned the hose on my face to take the heat away. Not even a blister. I was really lucky not to have been blinded. __________________ ~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA Last edited by Steeveedee; 07-18-2020 at 08:26 PM. Reason: typo

07-18-2020, 06:02 PM	#11
garyd1961 Registered User Join Date: May 2016 Location: Henderson NC Posts: 975	Re: Cooling system gremlin Before I got a real overflow bottle I just used a jug with a hole in the top. I placed it in the hole down by the horns and used a long overflow hose to reach. You need the right cap also.

07-19-2020, 08:18 AM	#12
custom10nut Registered User Join Date: Apr 2015 Location: East Tn (In the heart of the Smoky Mtns) Posts: 1,864	Re: Cooling system gremlin My gremlin is with the “Gauge Reading“(Original 70 in W/gage dash panel). I have an issue with the needle on the gauge making a steady climb until it pegs on the right side, of course this SHOWS overheated. I just went through and Put in a new sending unit, t-stat, and Water pump, and still the gauge does the same. After replacing everything I filled it back up, and let it burp all the air bubbles out, then I used a thermometer at the radiator cap the check the temp, and it stays right around 155 degrees. After the T-stat opens I can watch the coolant flowing so I know I’m getting circulation, I’ve read that Auto Wire has a sending unit made to original specs for the Gen 1 engines (prior to 1978, according to their site). I want to fix this issue, but I’m getting tired of buying new parts, thinking it fix it, only to find I still have the problem. Has anyone else used this AUTO WIRE sending unit, and did it work?



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