4.3 Blazer overheating quickly.

sjkelly11 · 05-27-2008, 06:04 PM

My 1996 4.3 Blazer is overheating quickly. I have a new radiator,cap and the heater core has been bypassed. I have removed the therostat and it still overheats after about 20 miniutes of driving. I'm not losing any fluid from the radiator or reservoir and don't notice any steam coming out of the exaust. Does this mean the dreaded head gaskets are gone?

Any help from past or present experiences is appreciated.

AE86 SR5 · 05-27-2008, 06:16 PM

My buddys mustang was just the same way. Did you try to flush it yet? you can just use a garden hose and clean it out it could be cloged, that mite also help you see if the head gasket is gone.

russell · 05-27-2008, 06:17 PM

I'd put a thermostat back in there if I was you. It'll let the coolant get real hot and circulate through the motor without it

MikeInCtown · 05-27-2008, 07:17 PM

Crack a heater hose or top rad hose to make sure there isn't some sort of vapor lock. After that I would run a flush type product through it and see what comes out. After that I'd be doing pressure tests in the cylinders and checking the spark plugs for any indication of a possible problem.

gchemist · 05-27-2008, 11:45 PM

Remove the radiator cap. Run the engine to operating temp. Is water flowing properly?
Do you have a shroud on the fan? Is the clutch working properly?

Yogi · 05-29-2008, 01:33 PM

Put the t-stat back in. It places some backpressure on the water pump, and without it, the pump will cavitate and stop pumping.

SH-60B · 05-29-2008, 02:35 PM

Quote: Originally Posted by sjkelly11

My 1996 4.3 Blazer is overheating quickly. I have a new radiator,cap and the heater core has been bypassed. I have removed the therostat and it still overheats after about 20 miniutes of driving. I'm not losing any fluid from the radiator or reservoir and don't notice any steam coming out of the exaust. Does this mean the dreaded head gaskets are gone?

Any help from past or present experiences is appreciated.

You need the thermostat to give the coolant in the radiator time to cool as already mentioned above.

lesterl · 05-31-2008, 11:24 PM

Also purge the air from the system besides the thermostat reinstall.

ZQ8 Blazer · 06-07-2008, 02:32 AM

check the oil for antifreeze, get a new thermostat, check the fluid in the radiator it can take a little bit for the antifreeze to settle, bypassing the heater core won't make it overheat.

You didn't change the radiator out did you? If so is it smaller than the original?

Are you using pure antifreeze, 50/50, or distilled water?

If it's none of those it's probably the waterpump.

05-27-2008, 06:04 PM	#1
sjkelly11 Registered User Age: 53 Join Date: May 2008 Posts: 1 Location: User is: OffLine	4.3 Blazer overheating quickly. My 1996 4.3 Blazer is overheating quickly. I have a new radiator,cap and the heater core has been bypassed. I have removed the therostat and it still overheats after about 20 miniutes of driving. I'm not losing any fluid from the radiator or reservoir and don't notice any steam coming out of the exaust. Does this mean the dreaded head gaskets are gone? Any help from past or present experiences is appreciated.
	[Reply w/Quote]

05-27-2008, 06:16 PM	#2
AE86 SR5 Registered User Join Date: Nov 2007 Posts: 751 Location: User is: OffLine	Re: 4.3 Blazer overheating quickly. My buddys mustang was just the same way. Did you try to flush it yet? you can just use a garden hose and clean it out it could be cloged, that mite also help you see if the head gasket is gone.
	[Reply w/Quote]

05-27-2008, 06:17 PM	#3
russell Whood'a Thought Age: 22 Join Date: Apr 2007 Posts: 3,862 Location: Durant,OK User is: OffLine	Re: 4.3 Blazer overheating quickly. I'd put a thermostat back in there if I was you. It'll let the coolant get real hot and circulate through the motor without it
	[Reply w/Quote]

05-27-2008, 07:17 PM	#4
MikeInCtown Registered User Age: 35 Join Date: Feb 2008 Posts: 927 Location: User is: OffLine	Re: 4.3 Blazer overheating quickly. Crack a heater hose or top rad hose to make sure there isn't some sort of vapor lock. After that I would run a flush type product through it and see what comes out. After that I'd be doing pressure tests in the cylinders and checking the spark plugs for any indication of a possible problem.
	[Reply w/Quote]

05-27-2008, 11:45 PM	#5
gchemist Registered User Join Date: May 2006 Posts: 356 Location: Austin User is: OffLine	Re: 4.3 Blazer overheating quickly. Remove the radiator cap. Run the engine to operating temp. Is water flowing properly? Do you have a shroud on the fan? Is the clutch working properly?
	[Reply w/Quote]

05-29-2008, 01:33 PM	#6
Yogi Registered (Ab) User Join Date: Feb 2008 Posts: 4,093 Location: League City, TX (Houston) User is: OffLine	Re: 4.3 Blazer overheating quickly. Put the t-stat back in. It places some backpressure on the water pump, and without it, the pump will cavitate and stop pumping.
	[Reply w/Quote]

05-29-2008, 02:35 PM	#7
SH-60B Registered Neanderthal Join Date: Nov 2007 Posts: 2,335 Location: Meriden/CT/USA User is: OffLine	Re: 4.3 Blazer overheating quickly. Quote: Originally Posted by sjkelly11 My 1996 4.3 Blazer is overheating quickly. I have a new radiator,cap and the heater core has been bypassed. I have removed the therostat and it still overheats after about 20 miniutes of driving. I'm not losing any fluid from the radiator or reservoir and don't notice any steam coming out of the exaust. Does this mean the dreaded head gaskets are gone? Any help from past or present experiences is appreciated. You need the thermostat to give the coolant in the radiator time to cool as already mentioned above.
	[Reply w/Quote]

05-31-2008, 11:24 PM	#8
lesterl Wire Splicin Fool :-) Age: 30 Join Date: May 2008 Posts: 4,413 Location: Harrisonville, MO User is: OffLine	Re: 4.3 Blazer overheating quickly. Also purge the air from the system besides the thermostat reinstall.
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06-07-2008, 02:32 AM	#9
ZQ8 Blazer ZQ8 Blazer Age: 26 Join Date: Jul 2004 Posts: 8,723 Location: Western, Ky User is: OffLine	Re: 4.3 Blazer overheating quickly. check the oil for antifreeze, get a new thermostat, check the fluid in the radiator it can take a little bit for the antifreeze to settle, bypassing the heater core won't make it overheat. You didn't change the radiator out did you? If so is it smaller than the original? Are you using pure antifreeze, 50/50, or distilled water? If it's none of those it's probably the waterpump.
	[Reply w/Quote]