overheating what else is left

**mhartwig** · 10-22-2010

Car overheats and has been outta commision for a month. First when driving home it overheated and i had a blown out hose. Since then I have replaced, upper hose, lower hose, bypass hose, reservoir hose, thermostat, lim gaskets (which were in bad shape), water pump, cooling fan relays, and a bunch of other things non coolant related.

The only thing left in the cooling system that I havent done is the radiator. Cooling fans are coming on, but one thing I noticed is I am getting no heat from the heater. I am getting AC, but only cold air. I have the knobs set to hot air and AC off.

2002 Pontiac Grand Prix SE 3.1L

**JoshsGTP** · 10-22-2010

have you back flushed the heater core?

**mhartwig** · 10-22-2010

No i have not. Not really sure how to do that.

**JoshsGTP** · 10-22-2010

Backflush cooling systems by purchasing a backflush kit at a local auto parts store. A backflush kit contains plastic T-tubes, a backflow prevention coupler and a plastic splash tube.

Allow your engine to cool completely before opening the radiator cap or disconnecting any hoses.

Cut the heater inlet hose with a utility knife. This is the hose that runs along the firewall from the radiator to the front of the engine. It is generally on the driver's side of the engine compartment.

Install the T-tube from the backflush kit that fits the heater inlet hose. Use the hose clamps that connect the inlet hose to the engine to tighten the T-tube securely.

Remove the radiator cap and install the splash tube from the backflush kit. It should snap right into place and form a seal.

Install the backflow prevention coupler from the backflush kit to the end of a garden hose. Hook up the other end of the hose to a faucet. Then connect the backflow prevention coupler to the T-tube you just installed on the end of the heater inlet hose.

Drain the radiator by opening the radiator plug at the bottom of the heater coils of the cooling systems. Use a plastic container to collect the fluid.

Reconnect the heater inlet hose to the engine using the remaining opening of the T-tube.

Start the engine of the car and turn the heater on high.

Turn on the faucet of the garden hose. Within a few seconds, you should start to see radiator fluid pour out of the plastic. You may want to use another plastic container to catch the fluid until clean water comes out.

Turn off the engine.

Turn off the water faucet and disconnect the garden hose from the coupler.

Remove the plastic splash tube from the top of the radiator.

Allow the water to completely drain from the cooling system. Close the radiator plug at the bottom of the heater core.

Seal the T-tube with the cap supplied with the kit and refill the radiator with coolant or anti-freeze.

**Jakegday** · 10-22-2010

your car overheats and your heater blows cold??? sounds like air in the system or low coolant

**sgtsnake** · 10-22-2010

My guess is bad thermostat. I had the same problem with my Venture, no heat and radiator cold to the touch.

I went through 8 of them to find a good one. Stant has a bad quality control problem. The 8th time I replaced it I bought three and put them in boiling water and only 1 out of the 3 was good!!!

**mhartwig** · 10-22-2010

I am going to try and bypass the heater core and see if it still overheats. I have another heater core but looks like a major pita. I have already tried bleeding it and replaced the tstat.

Would a clogged heater core make the car overheat. I googled that question and get conflicting answers.

**Whiplash Performance** · 10-22-2010

Originally Posted by mhartwig

I am going to try and bypass the heater core and see if it still overheats. I have another heater core but looks like a major pita. I have already tried bleeding it and replaced the tstat.

Would a clogged heater core make the car overheat. I googled that question and get conflicting answers.

Some older cars has a valve to allow coolant to flow into the heater core when the heater is turned on, so a clogged heater core wont cause you to overheat.

Did you bleed your cooling system by taking the radiator cap off and rev the car to about 1500 rpms and fill as the level goes down?

**mhartwig** · 10-22-2010

I turned the bleeder screw to bleed it.

**mhartwig** · 10-23-2010

Ok so I rented the compression tester from autzone. I pumped it up and noticed a few leaks. I put some gasket maker to seal the metal coolant bar to the engine.

Tried the compression tester again and didnt notice any more leaks. It kept compression. I drove it around and it over heated again. Bled the air out from the bleeder screw and drove some more. Kept bleeding air and it kept overheating.

I noticed the hoses I can pinch all the way down. They should be hard from the pressure right? The upper hose should be hot but it is not. Neither are the two heater hoses.

**Jakegday** · 10-23-2010

try removing your thermostat, and see if it continues to overheat. no the hoses should not be hard, pressure only gets up to like 16psi

**brand121** · 10-23-2010

is your coolant level gonig down? i ask bc you say that you keep bleeding the system... If so check the plastic elbows that come out of the intake and into the alternator mounting bracket, they are $4 and can cause the overheating if they are leaking at all...

**mhartwig** · 10-23-2010

I dont have the coolant elbows because mines the 3.1. I ordered the rad and a heater core. In the meantime, I am going to try the thermostat again. Maybe it is possible I got a bad one out of the box.

**brand121** · 10-23-2010

yea, sorry bout that, didn't see that you had the 3.1 til after I had posted that, was just trying to think what the hell else could be causing that thing to overheat...

I would try flushing the whole system like JoshsGTP recommended...

**sgtsnake** · 10-25-2010

My guess is still thermostat, upper hose cold is the key. Is the radiator cool to the touch after the engine is warm??? Fluid not getting past the thermostat if that's the case. I'm not kidding when I said i went through 8 new thermostats to find 1 good one.

**BOOSTED GP** · 10-25-2010

are you running dex cool? i have heard of it gumming up in the radiator and causing overheating problems. double check that the t-stat is working. simply holding a lighter under it will at least show if it is opening.

**mhartwig** · 10-25-2010

Yeah I am running dex. I have gunk in my reservoir and had coolant in my oil before I did the lims. Dont have that problem any more. Maybe the sludge clogged my rad.

I put in a new tstat but didnt check to see if the new tstat actually worked or not before hand. Just assumed that since it was new it probably worked.

Ill try testing the tstat, I also got a new heater core, and radiator to try.

**BOOSTED GP** · 10-25-2010

good luck to you. if none of that works then I am affraid i am stumped as well. I would however recommend switching to the green stuff when you get the problem fixed. The green stuff has never let me down nor anyone else I know.

**darkhorizon** · 10-26-2010

I made a custom bleeder for one of the 3.1 cars I had... I always had problems getting it bled.

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