No heat when not on throtle... COLD...

Strange situation ...

When I am driving and on the throttle/ (gas) the heat comes out blasting ... As soon as I let of gas say at stop light the air from the heater vents is COLD...

Any ideas where to check ?

Ryan

Coolant level and condition.

Heater core may be plugging up.

Coolant level and condition.

Heater core may be plugging up.

Exactly, just had this last week and the coolant level was very low.

I certainly have some sort of coolant leak that's for sure... I keep topping it up and can't find where its going ... I never see any drips under the vehicle... But I'll ceck and see how low it is....

I had it flushed last year and have added two - three jugs since.. ( at least) so whatever coolant is in there is in pretty good shape... But Thanks for the tips I'll check it again...

Ryan

If it is leaking and you can not se where it is going.

They make a leak test dye for coolant.
Add some and drive and then pressure test and check for leaks.
Check cold and warm and hot.

What year and modle and engine and mileage?
Has intake gasket ever been replaced?

yes, yes, my 02 has the glorious intake gasket leak hope you find the problem possibly the thermostat maybe its not opening all the way but just enough to when you giv it gas and spins the water pump faster pushing more coolant thru making the heat hotter under acceleration defianly check the level tho mine takes forever to warm up when she gets low

Intake gaskets can leak internally causing the oil level to rise. When this happens it leaves a "milk shake" looking goo on the underside of the oil fill cap. It usually causes the lifters to make noise, especially when the engine is cold also. As MT mentioned, top off and bleed air out, then pressure test and watch closely for pressure to drop.

If the intake gaskets are replaced with the factory style plastic frame and silicone rubber seal, they will leak again, guaranteed. Felpro makes a steel frame gasket with a rubber seal that, if installed and torqued properly, will not leak. The Felpro part number is MS98002T.

Thanks guys I always appreciate people responding it makes the forum very useable and user friendly - unlike other forums (not here) where others post comments that have no value what so ever...

My radiator was totally down ... took 3/4 of a jug ... but still have not found the leak will have to do a pressure test as suggested and check oil to see if its in there... my oil pressure gauge on the dash jumps all over the place ... and i thought that was just another cute GMC gremlin - as I have the non functioning fuel gauge as well problem where it jumps all over the place... :P

Thanks for the part number on the gasket. - is it a job I can do my self in my drive way ?

Truck is a 2000
168,000 KMS ( 110,000 miles or so)


on a side note my truck is text book case for this forum
so far:
- had wheel bearing problems
- no having wheel speed sensor problems
- gas gauge not working bouncing around
- 4x4 shifting issues - replaced shift module by kicker last week it worked once perfect now not working again ( although there is a TON of corrosion on the plug that I had to clean up)

Thanks guys I always appreciate people responding it makes the forum very useable and user friendly - unlike other forums (not here) where others post comments that have no value what so ever...

My radiator was totally down ... took 3/4 of a jug ... but still have not found the leak will have to do a pressure test as suggested and check oil to see if its in there... my oil pressure gauge on the dash jumps all over the place ... and i thought that was just another cute GMC gremlin - as I have the non functioning fuel gauge as well problem where it jumps all over the place... :P

Thanks for the part number on the gasket. - is it a job I can do my self in my drive way ?

Truck is a 2000
168,000 KMS ( 110,000 miles or so)


on a side note my truck is text book case for this forum
so far:
- had wheel bearing problems
- no having wheel speed sensor problems
- gas gauge not working bouncing around
- 4x4 shifting issues - replaced shift module by kicker last week it worked once perfect now not working again ( although there is a TON of corrosion on the plug that I had to clean up)

air in the heater core. When you are on the gas you spins the coolant pump faster and force coolant into the heater core.

Put the front of your truck on ramps with the rad being the top part of the engine and take off your rad cap and monitor the loss of coolant and replace your rad cap.

Your rad may be low due to the faulty rad caps with these trucks. Any stant will work fine. Just don't get an ac delco.

I burped my truck and it has been fine ever since and I had the same problem.

Read this thread from the "How To" section

http://www.automotiveforums.com/vbulletin/showthread.php?t=729213&highlight=basic+cooling+system+advice

This would be more specific for his problem:

http://www.automotiveforums.com/vbulletin/showthread.php?t=469926

This would be more specific for his problem:

http://www.automotiveforums.com/vbulletin/showthread.php?t=469926
Hey Dude, good to see ya in the Blazer forum again. How ya been?

BlazerLT
Long Time no see.

Welcome Back.