Getting hot issue - The 1947 - Present Chevrolet & GMC Truck Message Board Network

panhead59 · 03-28-2021, 05:56 PM

Stock 350 in a 68. Coolant temp. Goes up fast over 55 mph. Old issue, nothing new. 160 thermostat, good tight clutch fan with 7 blade fan. Good shroud. Fan 1/2 in, 1/2 out. Runs 170-180 all day long in city. Say below 55. Goes to 220 and probably would go higher if i let it over 55 mph. 50/50 mix coolant. Just changed radiator cap, of course it won't be that easy. Timing set at 10.5 btdc. 12 is too much. Thoughts ?

jimijam00 · 03-28-2021, 07:03 PM

The blade, clutch, and shroud have nothing to do with cooling at the speed, so you can rule all that stuff out.

My guess is you need a better radiator.

**'68OrangeSunshine** · 03-28-2021, 07:26 PM

What radiator are you running?
[Semper Fi]

panhead59 · 03-28-2021, 08:00 PM

Running a 2 row now. Upon further inspection, it is shot. Recommendations?

**Steeveedee** · 03-28-2021, 08:12 PM

A re-core of your radiator, if a lot of tubes have been soldered shut in previous work, would be enough. Seems like it's cheaper to buy a new radiator, though. Without AC, I've gotten 2-row radiators from O'Reilly reasonably cheap, like about $200. Of course that was several years ago.

**'68OrangeSunshine** · 03-28-2021, 08:44 PM

I live in AZ full time. I have a 4-tier core radiator on the 350 V8 in my '71 GMC Jimmy, and a 3-tier core in my '68 C/10 Stepside w/ 292 L6. [I'ts also the wider V8 style radiator, since the narrower L6 radiators became unavailable.] I use a 50/50 Prestone mix in both.
After some high heat issues on the 292, last summer, I flushed the system, put on new hoses and fresh coolant, and it runs fine. The 350 runs cool now too.
Can't remember what degree settings my thermostats are, but they're around 180 - 195*.
Too low a T-stat, and it just opens early, and the water sluices around, without spending time in the radiator to cool off.
For a moderate climate like VA, a 3-tier core might work. Four would be too much.

**Stocker** · 03-29-2021, 12:47 AM

When my all-metal 4-row needs replacing, I'm strongly considering a heavy-duty 2-row aluminum radiator.

**Grumpy old man** · 03-29-2021, 01:18 AM

Does your truck have a spring in the lower radiator hose ? A collapsing lower hose could explain your symptoms along with a clogged radiator .

**'68OrangeSunshine** · 03-29-2021, 05:30 AM

Personally I prefer the old school copper/brass radiator. With the aluminum you need to run the orange coolant.

panhead59 · 03-29-2021, 08:29 AM

Yes on the lower hose spring. Current radiator needs replacing. I went with a Cold Case direct fit alum. Radiator. I've had good results with the one in my GTO (with elec. Fans) so I'll try one in the truck. Minus the elec. Fans. I just bought some Prestone antifreeze that says "recommended for all vehicals makes, models and years." And it is clear
Looks like thick water. They've been around forever, so i guess i can trust their product. I think that green/yellow difference has most likely been improved upon.

**HO455** · 03-29-2021, 12:58 PM

Just be aware that Cold Case's "direct fit" is in reality just sort of direct fit and you will have to modify the factory mounts or fabricate new radiator mounts.

**Sheepdip** · 03-29-2021, 03:54 PM

Quote:

Originally Posted by panhead59

Stock 350 in a 68. Coolant temp. Goes up fast over 55 mph. Old issue, nothing new. 160 thermostat, good tight clutch fan with 7 blade fan. Good shroud. Fan 1/2 in, 1/2 out. Runs 170-180 all day long in city. Say below 55. Goes to 220 and probably would go higher if i let it over 55 mph. 50/50 mix coolant. Just changed radiator cap, of course it won't be that easy. Timing set at 10.5 btdc. 12 is too much. Thoughts ?

How old is the water pump. If it's old/worn those can be a cooling issue as they will cavitate more than pump.

gmc684x4 · 03-30-2021, 06:04 PM

A wide tube 2 row aluminum rad will cool better then a 4 core copper rad
Tstat to low
What psi is the rad cap and is the rad cap any good
A failed rad cap can cause overheat issues as well as worn water pump

I ran green Preston in my 99 for many years no issues

panhead59 · 04-06-2021, 09:23 AM

Update on new radiator. I went with a alum. 2 row from Cold Case. It solved problem of getting hot over 55mph. Old radiator was pretty rusted inside. Cold Case direct fit was just that- direct fit. The weld on top, by drivers side bracket wad/is a little thick. 5 min. Of grinding the top bracket was all that was needed. Fitment wasn't as easy when i put one in my 66 Gto, but very very easy and quick with 68 pickup. I'll put 180 degree thermo. Back in now. Used Prestone antifreeze listed for all radiator materials. It is green in color. I would highly recommend this radiator even though it's a little pricey at around $ 375.00.

**Steeveedee** · 04-06-2021, 10:55 AM

I've had that same model radiator in my truck for a couple years. Dropped right in and no trouble! Good to see that the problem is licked.

jimijam00 · 04-06-2021, 01:30 PM

Quote:

Originally Posted by panhead59

Update on new radiator. I went with a alum. 2 row from Cold Case. It solved problem of getting hot over 55mph.

jbarron · 04-06-2021, 04:26 PM

I'm betting on a timing issue. Is the vacuum advance working.

jimijam00 · 04-06-2021, 04:34 PM

Quote:

Originally Posted by jbarron

I'm betting on a timing issue. Is the vacuum advance working.

$500 says you are wrong.

GASoline71 · 04-07-2021, 12:06 AM

Quote:

Originally Posted by '68OrangeSunshine

Personally I prefer the old school copper/brass radiator. With the aluminum you need to run the orange coolant.

Been using a 2 row aluminum radiator for 12 years and using Prestone "green" coolant mixed 50/50 with distilled water... No problems...

Gary

**'68OrangeSunshine** · 04-07-2021, 01:10 AM

Quote:

Originally Posted by GASoline71

Been using a 2 row aluminum radiator for 12 years and using Prestone "green" coolant mixed 50/50 with distilled water... No problems...

Gary

OK. Must be an urban myth. Any dis-similar metal corrosion if you have a copper/brass heater core and an aluminum radiator?
I prefer the green Prestone myself.

72c20customcamper · 04-07-2021, 09:50 PM

Quote:

Originally Posted by '68OrangeSunshine

OK. Must be an urban myth. Any dis-similar metal corrosion if you have a copper/brass heater core and an aluminum radiator?
I prefer the green Prestone myself.

Been running green in my Chevelle for 8 or 9 years with an aluminum radiator this is what DeWitt calls for with distilled water. Only had one problem but I dont think the antifreeze was the problem

**Stocker** · 04-07-2021, 09:57 PM

Ouch!!

**'68OrangeSunshine** · 04-08-2021, 01:24 AM

Ouch, too.

03-28-2021, 05:56 PM	#1
panhead59 Registered User Join Date: Feb 2012 Location: Vinton, Va. Posts: 493	Getting hot issue Stock 350 in a 68. Coolant temp. Goes up fast over 55 mph. Old issue, nothing new. 160 thermostat, good tight clutch fan with 7 blade fan. Good shroud. Fan 1/2 in, 1/2 out. Runs 170-180 all day long in city. Say below 55. Goes to 220 and probably would go higher if i let it over 55 mph. 50/50 mix coolant. Just changed radiator cap, of course it won't be that easy. Timing set at 10.5 btdc. 12 is too much. Thoughts ? __________________ "You are not forgotten" USMC 75-79 (Aviation Ordnance Tech- F-4 Phantom) 1959 H-D Panhead. Owned since 1978. Currently with son in Lawton, OK. 1968 Chevy Custom SWB pick up. Fleetside. Lowered 4/6. Totally refurbished. 1966 Pontiac GTO. 4 speed. Saved original 389. Now has slightly built 455 engine. 355 rear gears. Very fun to drive !

03-28-2021, 07:03 PM	#2
jimijam00 Registered User Join Date: Apr 2009 Location: PNW Posts: 553	Re: Getting hot issue The blade, clutch, and shroud have nothing to do with cooling at the speed, so you can rule all that stuff out. My guess is you need a better radiator.

03-28-2021, 07:26 PM	#3
'68OrangeSunshine Senior Member Join Date: Feb 2002 Location: Tucson, AZ USA Posts: 7,504	Re: Getting hot issue What radiator are you running? [Semper Fi] __________________ Every 25 years I like to rebuild that 292, whether it needs it or not.

03-28-2021, 08:00 PM	#4
panhead59 Registered User Join Date: Feb 2012 Location: Vinton, Va. Posts: 493	Re: Getting hot issue Running a 2 row now. Upon further inspection, it is shot. Recommendations? __________________ "You are not forgotten" USMC 75-79 (Aviation Ordnance Tech- F-4 Phantom) 1959 H-D Panhead. Owned since 1978. Currently with son in Lawton, OK. 1968 Chevy Custom SWB pick up. Fleetside. Lowered 4/6. Totally refurbished. 1966 Pontiac GTO. 4 speed. Saved original 389. Now has slightly built 455 engine. 355 rear gears. Very fun to drive !

03-28-2021, 08:12 PM	#5
Steeveedee Who Changed This? Join Date: Jan 2013 Location: Simi Valley, CA Posts: 10,677	Re: Getting hot issue A re-core of your radiator, if a lot of tubes have been soldered shut in previous work, would be enough. Seems like it's cheaper to buy a new radiator, though. Without AC, I've gotten 2-row radiators from O'Reilly reasonably cheap, like about $200. Of course that was several years ago. __________________ ~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA

03-28-2021, 08:44 PM	#6
'68OrangeSunshine Senior Member Join Date: Feb 2002 Location: Tucson, AZ USA Posts: 7,504	Re: Getting hot issue I live in AZ full time. I have a 4-tier core radiator on the 350 V8 in my '71 GMC Jimmy, and a 3-tier core in my '68 C/10 Stepside w/ 292 L6. [I'ts also the wider V8 style radiator, since the narrower L6 radiators became unavailable.] I use a 50/50 Prestone mix in both. After some high heat issues on the 292, last summer, I flushed the system, put on new hoses and fresh coolant, and it runs fine. The 350 runs cool now too. Can't remember what degree settings my thermostats are, but they're around 180 - 195*. Too low a T-stat, and it just opens early, and the water sluices around, without spending time in the radiator to cool off. For a moderate climate like VA, a 3-tier core might work. Four would be too much. __________________ Every 25 years I like to rebuild that 292, whether it needs it or not.

03-29-2021, 12:47 AM	#7
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,722	Re: Getting hot issue When my all-metal 4-row needs replacing, I'm strongly considering a heavy-duty 2-row aluminum radiator. __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

03-29-2021, 01:18 AM	#8
Grumpy old man Senior Member Join Date: Dec 2013 Location: Gods country East,Tn Posts: 8,545	Re: Getting hot issue Does your truck have a spring in the lower radiator hose ? A collapsing lower hose could explain your symptoms along with a clogged radiator . __________________ 1967 Factory short bed - Old school '71 - 350 / 4bolt / 487 heads / Edelbrock C3BX Muncie M-22 4 speed / Hurst Comp plus Factory 12 bolt posi 3.73 / 255-70-15 Smoothed firewall / Factory cowl induction Power disc brakes / power steering / 3.5-5" drop

03-29-2021, 05:30 AM	#9
'68OrangeSunshine Senior Member Join Date: Feb 2002 Location: Tucson, AZ USA Posts: 7,504	Re: Getting hot issue Personally I prefer the old school copper/brass radiator. With the aluminum you need to run the orange coolant. __________________ Every 25 years I like to rebuild that 292, whether it needs it or not.

03-29-2021, 08:29 AM	#10
panhead59 Registered User Join Date: Feb 2012 Location: Vinton, Va. Posts: 493	Re: Getting hot issue Yes on the lower hose spring. Current radiator needs replacing. I went with a Cold Case direct fit alum. Radiator. I've had good results with the one in my GTO (with elec. Fans) so I'll try one in the truck. Minus the elec. Fans. I just bought some Prestone antifreeze that says "recommended for all vehicals makes, models and years." And it is clear Looks like thick water. They've been around forever, so i guess i can trust their product. I think that green/yellow difference has most likely been improved upon. __________________ "You are not forgotten" USMC 75-79 (Aviation Ordnance Tech- F-4 Phantom) 1959 H-D Panhead. Owned since 1978. Currently with son in Lawton, OK. 1968 Chevy Custom SWB pick up. Fleetside. Lowered 4/6. Totally refurbished. 1966 Pontiac GTO. 4 speed. Saved original 389. Now has slightly built 455 engine. 355 rear gears. Very fun to drive !

03-29-2021, 12:58 PM	#11
HO455 Post Whore Join Date: Feb 2016 Location: Portland Oregon Posts: 11,350	Re: Getting hot issue Just be aware that Cold Case's "direct fit" is in reality just sort of direct fit and you will have to modify the factory mounts or fabricate new radiator mounts. __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377

03-30-2021, 06:04 PM	#13
gmc684x4 Registered User Join Date: Jul 2012 Location: Whitehorse yukon Posts: 1,218	Re: Getting hot issue A wide tube 2 row aluminum rad will cool better then a 4 core copper rad Tstat to low What psi is the rad cap and is the rad cap any good A failed rad cap can cause overheat issues as well as worn water pump I ran green Preston in my 99 for many years no issues

04-06-2021, 09:23 AM	#14
panhead59 Registered User Join Date: Feb 2012 Location: Vinton, Va. Posts: 493	Re: Getting hot issue Update on new radiator. I went with a alum. 2 row from Cold Case. It solved problem of getting hot over 55mph. Old radiator was pretty rusted inside. Cold Case direct fit was just that- direct fit. The weld on top, by drivers side bracket wad/is a little thick. 5 min. Of grinding the top bracket was all that was needed. Fitment wasn't as easy when i put one in my 66 Gto, but very very easy and quick with 68 pickup. I'll put 180 degree thermo. Back in now. Used Prestone antifreeze listed for all radiator materials. It is green in color. I would highly recommend this radiator even though it's a little pricey at around $ 375.00. __________________ "You are not forgotten" USMC 75-79 (Aviation Ordnance Tech- F-4 Phantom) 1959 H-D Panhead. Owned since 1978. Currently with son in Lawton, OK. 1968 Chevy Custom SWB pick up. Fleetside. Lowered 4/6. Totally refurbished. 1966 Pontiac GTO. 4 speed. Saved original 389. Now has slightly built 455 engine. 355 rear gears. Very fun to drive !

04-06-2021, 10:55 AM	#15
Steeveedee Who Changed This? Join Date: Jan 2013 Location: Simi Valley, CA Posts: 10,677	Re: Getting hot issue I've had that same model radiator in my truck for a couple years. Dropped right in and no trouble! Good to see that the problem is licked. __________________ ~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA

04-06-2021, 04:26 PM	#17
jbarron Registered User Join Date: Apr 2006 Location: Spring, Texas Posts: 167	Re: Getting hot issue I'm betting on a timing issue. Is the vacuum advance working. __________________ '72 3/4 Cheyenne Super 402/TH400 Gear Vendors '72 3/4 Cheyenne Super 350/200R4 '50 1/2 Chevy 3 Window



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04-07-2021, 09:57 PM	#22
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,722	Re: Getting hot issue Ouch!! __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

04-08-2021, 01:24 AM	#23
'68OrangeSunshine Senior Member Join Date: Feb 2002 Location: Tucson, AZ USA Posts: 7,504	Re: Getting hot issue Ouch, too. __________________ Every 25 years I like to rebuild that 292, whether it needs it or not.

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