Radiator Question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Tynee · 08-02-2002, 09:57 PM

Hey, guys. LONG time no see. Work has been hectic. Thats what its like in a construction related trade, huh. My problem is that even with a brand new water pump and the thermostat completely out, the truck still runs hot, especially at highway speeds. Will removing the radiator and having it boiled out fix the problem, or is this just a poorly designed cooling system (all factory) that needs to be upgraded?

67 SS · 08-02-2002, 10:14 PM

Are your radiator fins blocked?(bugs, leaves,etc.)What about the hoses?They could be weak and collapsing.

Tynee · 08-02-2002, 10:20 PM

Most hoses new around christmas time, and don't look colapsed (I assume you can tell by looking) Fins are clear.

Super Chevy · 08-02-2002, 10:30 PM

Try putting the thermostate back in,there was a thread about this not to long ago... Might help,and what kind of fan(s) are you running?

67 SS · 08-02-2002, 10:34 PM

You can't always tell by just looking at the hoses.I had to work on a car at Tech school that the hoses would collapse after it ran for a while and got hot.Try putting a big fan in front of the truck blowing through the radiator and just let it idle.You should be able to see if they collapse.If they do get hoses with wire inserts.What about the fan and shroud,what are they and what shape are they in?

*Zkast* · 08-02-2002, 10:44 PM

*most* highway overheating problems come from restricted radiators. Get the thermostat back in there

There are a few checks you can do using a thermometer to find out if the radiator is restricted or you can simply pull it and have it cleaned. If its been a while since thats been done/or never done at all, I would strongly suggest that have that done. You know you have good airflow across the radiator because of ram air (60mph air hitting the front of the truck) So its a matter of coolant flowing through the radiator either too fast (no thermostat) or too slowely (restricted radiator)

There are other things that will cause this problem but the radiator is the simplest and most probable.

70cstguy · 08-02-2002, 11:02 PM

Put thermastat back in. Get a 165 degree one if you can. Check clutch fan (if your running one). check timing, if it is still running hot ,upgrade to 4 row rad.

Tynee · 08-02-2002, 11:06 PM

Thank you gentlemen, I've been reading some of the other posts on this issue (Isn't the search option great?) and have come to the conclusion that I need to put the thermo back in and change the bottom hose before I pull the radiator. Of course yanking the Rad couldn't hurt anyway.

Longhorn Man · 08-02-2002, 11:56 PM

If it is an A/C truck, look at teh condenser, hold a flash light by the fan (eng off of course) and look at the light coming through. If it looks restrivcted, take it to a coin op car wash, and blast it from the engine side.
Pop open the cap...look at the tubes down in there. How bad is the nasty scaley crap? That is the other thing to look at on the rad.
If you replace the Rad, (or get it rodded) only run purified drinking water in it. (esp if you are in a hard water area) It will reduce (if not prevent) the scaley crap from 'growing' back.

Huck · 08-03-2002, 08:08 AM

IMHO probability---Radiator filled with crap -(inside and /or outside) -I know there are a lot of other possible things but---9-10 if it runs hot at highway speed-with thermostat out--radiator not doing the job. Fan not an issue---even if an A/C condenser is blocking---you still have plenty of air flow above and below to cool. IF you pull raidator to have it cleaned---check prices of new 4row at Radiator.com first. Hear tell they deliver to your door at a very competative price in a day or two. Replace hoses upon re-install! You'll never regret it. In Ky, our tap water has more junk in it then the river!!! Good luck----Huck

O'l Buck · 08-04-2002, 03:29 AM

a different radiator fixed mine, the old one had so much crap in it it weight about 75 pounds.....plus having about 1/4 of the core blocked off by the previous owner didn't help matters anyway.....I sure was glad I bought that 91 lumina van cheap from F I L....almost a perfect fit and it's got me running about 180 degrees all the time, just like God intended for my truck to run.

dwaite72lnghrn · 08-04-2002, 07:45 AM

If the radiator looks good with a flash light no corrosion I would double check the timing. It can cause it to run Hot at highway speed.

RipMeyer · 08-04-2002, 11:02 AM

Are you only using the stock gage in the inst panel? What do you consider hot? 180 to 205 is about normal. Dont forget to get a new cap. It could be bad and you would never know it. Bad caps can cause high temps.

ChevLoRay · 08-04-2002, 11:13 AM

....and the reason for re-installing the thermostat is this: water and coolant must spend enough time IN the radiator to cool. When the thermostat is removed, the coolant is forced to travel through the radiator as quickly as the water pump can move it. Just imagine that you are sweating and a puff of air passes you by. You might have enjoyed that brief exposure to it, but it didn't do you any real good. Now, imagine that you are hot and sweaty and you find a ceiling fan (a good one) to stand under. How much better does THAT feel? Do your engine a favor and reinstall that thermostat so the coolant can enjoy that stay in the radiator and thereby keep your engine cooler.

08-02-2002, 09:57 PM	#1
Tynee I miss this truck. Join Date: Dec 2001 Location: Lexington, KY U.S.A. Posts: 2,863	Radiator Question Hey, guys. LONG time no see. Work has been hectic. Thats what its like in a construction related trade, huh. My problem is that even with a brand new water pump and the thermostat completely out, the truck still runs hot, especially at highway speeds. Will removing the radiator and having it boiled out fix the problem, or is this just a poorly designed cooling system (all factory) that needs to be upgraded? __________________ '07 GMC Acadia SLT. Sweet ride. '08 Crew Cab Z-71 short bed. Really like this truck A LOT.

08-02-2002, 10:20 PM	#3
Tynee I miss this truck. Join Date: Dec 2001 Location: Lexington, KY U.S.A. Posts: 2,863	Most hoses new around christmas time, and don't look colapsed (I assume you can tell by looking) Fins are clear. __________________ '07 GMC Acadia SLT. Sweet ride. '08 Crew Cab Z-71 short bed. Really like this truck A LOT.

08-02-2002, 11:02 PM	#7
70cstguy Registered User Join Date: Nov 2001 Location: Travelers Rest SC. Posts: 79	Put thermastat back in. Get a 165 degree one if you can. Check clutch fan (if your running one). check timing, if it is still running hot ,upgrade to 4 row rad. __________________ 70 cst/10 swb 350/350 ugly olive green, but very straight and little rust.

08-02-2002, 11:06 PM	#8
Tynee I miss this truck. Join Date: Dec 2001 Location: Lexington, KY U.S.A. Posts: 2,863	Thank you gentlemen, I've been reading some of the other posts on this issue (Isn't the search option great?) and have come to the conclusion that I need to put the thermo back in and change the bottom hose before I pull the radiator. Of course yanking the Rad couldn't hurt anyway. __________________ '07 GMC Acadia SLT. Sweet ride. '08 Crew Cab Z-71 short bed. Really like this truck A LOT.

08-04-2002, 03:29 AM	#11
O'l Buck Recovering Truck Driver Join Date: Mar 2002 Location: Orleans, NE USA Posts: 1,883	a different radiator fixed mine, the old one had so much crap in it it weight about 75 pounds.....plus having about 1/4 of the core blocked off by the previous owner didn't help matters anyway.....I sure was glad I bought that 91 lumina van cheap from F I L....almost a perfect fit and it's got me running about 180 degrees all the time, just like God intended for my truck to run. __________________ 67 K-20 350, SM465, Eaton rear, 4.56 no spin option 00 Dodge 2500 4x4, 24V cummins, 5 speed Chad South Central Nebraska

08-02-2002, 10:14 PM	#2
67 SS Registered User Join Date: Jun 2002 Location: NW ARKANSAS Posts: 258	Are your radiator fins blocked?(bugs, leaves,etc.)What about the hoses?They could be weak and collapsing.

08-02-2002, 10:30 PM	#4
Super Chevy Registered User Join Date: Feb 2001 Location: Ohio Posts: 1,025	Try putting the thermostate back in,there was a thread about this not to long ago... Might help,and what kind of fan(s) are you running?

08-02-2002, 10:34 PM	#5
67 SS Registered User Join Date: Jun 2002 Location: NW ARKANSAS Posts: 258	You can't always tell by just looking at the hoses.I had to work on a car at Tech school that the hoses would collapse after it ran for a while and got hot.Try putting a big fan in front of the truck blowing through the radiator and just let it idle.You should be able to see if they collapse.If they do get hoses with wire inserts.What about the fan and shroud,what are they and what shape are they in?

08-02-2002, 10:44 PM	#6
Zkast Account Suspended Join Date: May 2002 Location: Olathe, Kansas Posts: 929	most highway overheating problems come from restricted radiators. Get the thermostat back in there There are a few checks you can do using a thermometer to find out if the radiator is restricted or you can simply pull it and have it cleaned. If its been a while since thats been done/or never done at all, I would strongly suggest that have that done. You know you have good airflow across the radiator because of ram air (60mph air hitting the front of the truck) So its a matter of coolant flowing through the radiator either too fast (no thermostat) or too slowely (restricted radiator) There are other things that will cause this problem but the radiator is the simplest and most probable.

08-02-2002, 11:56 PM	#9
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	If it is an A/C truck, look at teh condenser, hold a flash light by the fan (eng off of course) and look at the light coming through. If it looks restrivcted, take it to a coin op car wash, and blast it from the engine side. Pop open the cap...look at the tubes down in there. How bad is the nasty scaley crap? That is the other thing to look at on the rad. If you replace the Rad, (or get it rodded) only run purified drinking water in it. (esp if you are in a hard water area) It will reduce (if not prevent) the scaley crap from 'growing' back.

08-03-2002, 08:08 AM	#10
Huck Senior Member Join Date: Jun 2001 Location: Shelbyville, KY Posts: 3,261	IMHO probability---Radiator filled with crap -(inside and /or outside) -I know there are a lot of other possible things but---9-10 if it runs hot at highway speed-with thermostat out--radiator not doing the job. Fan not an issue---even if an A/C condenser is blocking---you still have plenty of air flow above and below to cool. IF you pull raidator to have it cleaned---check prices of new 4row at Radiator.com first. Hear tell they deliver to your door at a very competative price in a day or two. Replace hoses upon re-install! You'll never regret it. In Ky, our tap water has more junk in it then the river!!! Good luck----Huck

08-04-2002, 07:45 AM	#12
dwaite72lnghrn Registered User Join Date: Jun 2002 Location: central pa Posts: 1,525	If the radiator looks good with a flash light no corrosion I would double check the timing. It can cause it to run Hot at highway speed. __________________ 72 longhorn c30 502BB/th400/fact air/4.11rear/ custom camper 72 bug(the better half's) under reconstruction 2009 HHR aqua blue 71 GMC k20 350/sm465 2009 Chevy hd3500 6.6 Victory Red crew cab dually Dave & Jeanne

08-04-2002, 11:02 AM	#13
RipMeyer Registered User Join Date: Oct 2001 Location: Southern New Mexico Posts: 649	Are you only using the stock gage in the inst panel? What do you consider hot? 180 to 205 is about normal. Dont forget to get a new cap. It could be bad and you would never know it. Bad caps can cause high temps.

08-04-2002, 11:13 AM	#14
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	....and the reason for re-installing the thermostat is this: water and coolant must spend enough time IN the radiator to cool. When the thermostat is removed, the coolant is forced to travel through the radiator as quickly as the water pump can move it. Just imagine that you are sweating and a puff of air passes you by. You might have enjoyed that brief exposure to it, but it didn't do you any real good. Now, imagine that you are hot and sweaty and you find a ceiling fan (a good one) to stand under. How much better does THAT feel? Do your engine a favor and reinstall that thermostat so the coolant can enjoy that stay in the radiator and thereby keep your engine cooler. __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was.



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