engine temperature question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

erikh09 · 12-31-2012, 05:31 PM

Hello all,

I am scratching my head and hoping someone can lend a little advice. When I have my truck out for a ride (or just idleing for an extended time) my heater hoses both get hot, both radiator hoses get warm, but my radiator cap stays cold to the touch. Thermostat seems to be working (no antifreeze coming from overflow as if it is overheating) but I am not sure the gauge works. Why would the cap not be getting hot? Is the system working that efficiently?

By the way it is a 350 chevy mild street motor with mechanical fan

Thanks for any advice!

68gmsee · 12-31-2012, 06:47 PM

Does the top of the radiator or area around the cap get hot?

I'm not sure why, but the radiator water level may have something to do with it. If the truck is not overheating and level is down, there's not water getting to it.
These trucks, for the most part, run a few inches below the top unless you have an overflow tank that keeps the level full..

erikh09 · 01-01-2013, 05:38 PM

Nothing seems to get excessively hot. The heater hoses do get pretty hot to the touch but that is it. I will have to go check the level in the radiator to see where it is.

68gmsee · 01-01-2013, 06:23 PM

Quote:

Originally Posted by erikh09

Nothing seems to get excessively hot. The heater hoses do get pretty hot to the touch but that is it. I will have to go check the level in the radiator to see where it is.

Radiator probably will be about 2-3 inches low if it's like most trucks that don't have the overflow container. I got a new cap and installed an overflow tube on my GMC to keep the radiator topped.

Andy4639 · 01-01-2013, 06:33 PM

What temperature thermo does the truck have? Are you sure it's got a thermastat? Anytime you run the truck long enough to get it up to temperature and shut it off if it's filled correctly it should always run water into the over flow and then when it cools should suck it back in to the radator.
Check for level and leaks.

geezer#99 · 01-01-2013, 06:54 PM

Your rad cap doesn't get hot cause it's isolated from the rad by two gaskets. One on the seal to the flange and one on the pressure releif valve. If you have a non-return system like stock your level should be 1-2 inches below the top when cold. That's called an open system.
If you have a return system with a return bottle your level will be absolutely full when cold. THat's called a closed system.
You can have an open system with a catch can That doesn't return fluid to the rad. Only 1 hose into the can.
A closed system has 2 hoses. One hooked to the rad and immersed in the coolant in the bottle and one that vents to the ground.

12-31-2012, 05:31 PM	#1
erikh09 Registered User Join Date: Oct 2011 Location: Oxford,Pa Posts: 89	engine temperature question Hello all, I am scratching my head and hoping someone can lend a little advice. When I have my truck out for a ride (or just idleing for an extended time) my heater hoses both get hot, both radiator hoses get warm, but my radiator cap stays cold to the touch. Thermostat seems to be working (no antifreeze coming from overflow as if it is overheating) but I am not sure the gauge works. Why would the cap not be getting hot? Is the system working that efficiently? By the way it is a 350 chevy mild street motor with mechanical fan Thanks for any advice!

12-31-2012, 06:47 PM	#2
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: engine temperature question Does the top of the radiator or area around the cap get hot? I'm not sure why, but the radiator water level may have something to do with it. If the truck is not overheating and level is down, there's not water getting to it. These trucks, for the most part, run a few inches below the top unless you have an overflow tank that keeps the level full.. __________________ 68 GMC 250/3 speed Saginaw p/b p/s 69 Chevy 350/350 currently in pieces still lookin for a cab 06 Trailblazer I just want a vehicle that I can work on, that won't talk to me, leave error msgs or keep track of how I drive...

01-01-2013, 05:38 PM	#3
erikh09 Registered User Join Date: Oct 2011 Location: Oxford,Pa Posts: 89	Re: engine temperature question Nothing seems to get excessively hot. The heater hoses do get pretty hot to the touch but that is it. I will have to go check the level in the radiator to see where it is.

01-01-2013, 06:33 PM	#5
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: engine temperature question What temperature thermo does the truck have? Are you sure it's got a thermastat? Anytime you run the truck long enough to get it up to temperature and shut it off if it's filled correctly it should always run water into the over flow and then when it cools should suck it back in to the radator. Check for level and leaks. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

01-01-2013, 06:54 PM	#6
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,736	Re: engine temperature question Your rad cap doesn't get hot cause it's isolated from the rad by two gaskets. One on the seal to the flange and one on the pressure releif valve. If you have a non-return system like stock your level should be 1-2 inches below the top when cold. That's called an open system. If you have a return system with a return bottle your level will be absolutely full when cold. THat's called a closed system. You can have an open system with a catch can That doesn't return fluid to the rad. Only 1 hose into the can. A closed system has 2 hoses. One hooked to the rad and immersed in the coolant in the bottle and one that vents to the ground.



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