Overheating question

[Awd-Tsi]

Have a 95 blazer, when I have the heater on it only blows heat 25 percent of the time. During this time it starts heating up fairly high , almost into the red. Then the heater will kick in and it will cool down. Anyone know what's going on? Almost like coolant isn't flowing when it's not bowing hot air

[benyl]

Thermostat is stuck closed?

[Kloubek]

Thermostat shouldn't change with the HVAC.

My bet is on your heater core.

[Awd-Tsi]

I just did the thermostat a week ago . It helped a bit, but seems like coolant Isnt flowing ?

[master hec0]

if you dont care about heat just bypass the heater core.

[AE92_TreunoSC]

Heaters dont cause overheating really, unless there is an air pocket trapped, but usually those bleed out over time.

Quick way to check for coolant flow from the water pump is to pull a heater hose off while its cool and see if it pumps coolant. Makes a mess but it verifies a defective pump.



Do the upper and lower rad hoses share the same temperature after its warmed up?

[Awd-Tsi]

Originally posted by AE92_TreunoSC
Heaters dont cause overheating really, unless there is an air pocket trapped, but usually those bleed out over time.

Quick way to check for coolant flow from the water pump is to pull a heater hose off while its cool and see if it pumps coolant. Makes a mess but it verifies a defective pump.



Do the upper and lower rad hoses share the same temperature after its warmed up? Ill check this and see, thanks

[No_Cash]

A good way to bleed the air out if is just air, is to let it idle for about 15-20min with the rad cap off and it on hot/defrost, fan on high, and squeeze the upper rad hose a bunch of times.

[master hec0]

feeling the temp of the hoses is the best way. also do that with the heatercore hoses too thats an easy way to tell if its bad.

[Awd-Tsi]

Hmm, now the temperature gauge
shows it's at 40 degrees all the time and never moves up

[CapnCrunch]

Is it low on coolant? Sounds like it.

[Abeo]

What color is the coolant? Sounds like a large air bubble, facked water pump, or head gasket leak pressurizing the cooling system.

Take a look at the overflow tank, if its bubbling like a motherfucker when this is happening, its probably the head gasket

[sillysod]

Sounds like low coolant / air bubble or bad water pump

[master hec0]

when you went to waiparous didn't you have to stop and add water to your radiator? me thinks there is a connection.

[Awd-Tsi]

Originally posted by master hec0
when you went to waiparous didn't you have to stop and add water to your radiator? me thinks there is a connection. It never had any, I had the vehicle for like 3 days and didn't even check
it. It doesn't appear to be leaking

[sillysod]

Originally posted by Awd-Tsi
It never had any, I had the vehicle for like 3 days and didn't even check
it. It doesn't appear to be leaking

it doesn't have to leak to dissapear.

omm nom nom delicious antifreeze....

[Tik-Tok]

Originally posted by Awd-Tsi
I just did the thermostat a week ago . It helped a bit, but seems like coolant Isnt flowing ?

I don't mean to insult your mechanical aptitude... buttt... did you install it in the right direction?

Wrong direction = engine getting super hot, but no heat going to heater core (possibly, this is true on old school chev engines, I don't know about newer ones) heat soaking the thermostat to the point that it does eventually open, and you getting heat to your core, and engine cools down.

As engine cools, the thermostat starts closing again, and repeat.

[Awd-Tsi]

Originally posted by Tik-Tok


I don't mean to insult your mechanical aptitude... buttt... did you install it in the right direction?

Wrong direction = engine getting super hot, but no heat going to heater core (possibly, this is true on old school chev engines, I don't know about newer ones) heat soaking the thermostat to the point that it does eventually open, and you getting heat to your core, and engine cools down.

As engine cools, the thermostat starts closing again, and repeat. I installed it the same way the other one came out , made sure of it. The reason I did the thermostat is because of the same
problem, trying to fix it

[Tik-Tok]

Originally posted by Awd-Tsi
I installed it the same way the other one came out , made sure of it. The reason I did the thermostat is because of the same
problem, trying to fix it

It's possible the previous owner put it in backwards. I had this happen on an auto-choke spring for my '67 cougar, kept having idling issues after it was warmed up, and decided it was the choke spring, replaced it exactly as it came out, and it wasn't until I started it up and warmed it up that I realized the spring was backwards to begin with, so it was CLOSING the choke when it was warm :rofl: