overheat on a hill

[Some guy]

So this weekend i over heated the car in a parking garage. It drove down just fine, 40 minutes in la traffic. It seemed fine. then i pull into this parking garage, it was a steep incline. I have driven hills before, i didn't rev the engine to much. It seamed like in a matter of 2 minutes the car was red lined (temp gauge) and the coolant was boiling. so i pulled over let the car cool down in a parking spot. added water and had to buy a tool kit to bleed it again.


it seams like this would be caused by air in the lines. I was thinking of getting an auto air bleeder from special T


Has any one else had this problem? am i on the right path?

[AugustneverEnds]

Sorry to hear about your troubles!

Air in the cooling system is a definite possibilty. First thing to check for are leaks. Might be easy to spot like the radiator area or the otterstat or not so easy if a hose under the intake manifold is the problem.

Also you should check some simple stuff like if the thermostat is opening and if the cap on the header bottle is rated for 15 psi and if the valve on it is working.

Can you verify that your cooling fans are working?

Another possibility is a leaking head gasket but that's a worst case scenario (here's to hoping it's not!)

Keep us posted

[Jonathan]

Do you know how much coolant was in your reservoir prior to this happening?

Here is what I am thinking, albeit it not sure how likely it would be... if you were on a steep enough incline, with the front end way higher than the rear, you might have briefly starved the suction side of the water pump.

Think of it like how our fuel tanks change level when we go up and down hills. If your front end is higher, the level reads lower because the gas slops to the rear and away from the level sender that is near the front. If you go down a big hill and the front is lower than the rear, it reads higher because more fuel is slopping towards the sender.

The coolant reservoir has no baffles either and the larger diameter suction hose is on the front edge near the bottom. Conceivably, if it was too low already, you might not have kept that hose full and then induced air into the loop inadvertently. Or there was already air in the system, which might be more likely.

The pocket of air above the level in the reservoir is okay normally because it stays there. If your level was too low and then you tipped the front of the car up and exposed the opening of that suction hose to that air pocket, it might have caused what you saw.

I say this because you mentioned the car drove fine and didn't overheat in LA traffic. So it has something to do with the parking garage incline or it's one untimely coincidence.

Like Mr. SeptemberIsHereUnfortunately said, make sure the otterstat is turning the fans on properly and all that jazz.

[Some guy]

The fans were on when i turned the car off. But i was on a level part of the parking garage by this point. After i refilled and bled the system, i was able to drive another 45 minutes in traffic back home.

the level in the reserve was about 1/4 full. If i filled it up more, it would leak out the over flow when the car heats up. Maybe this is leading to a bad radiator cap?

I dont think there was a leak, it never smelled like it, and i didn't see any puddles underneath it.

i am still thinking of getting a the air bleeder.


It is weird because the cooling system has been fine for months.

[Bitsyncmaster]

My car never had overheating problems but when I went on the Auto-train (a very steep incline) it overheated on the drive after I got off the train. I'm guessing there was air somewhere trapped in the system and the incline made that a problem.

[David T]

My car never had overheating problems but when I went on the Auto-train (a very steep incline) it overheated on the drive after I got off the train. I'm guessing there was air somewhere trapped in the system and the incline made that a problem.

The cooling system should function equally well on level ground or on an incline. The only thing I can think of that could be affecting you is that you are low on coolant which implies you also have air in the system. Make sure the system is full of 50/50 anti-freeze and soft water. Thoroughly bleed the system. Several times if you have to. Make sure your Otterstadt switch is pointed down, especially if you have an early car. Make sure you have the uprated circuit breaker for the fans and you do NOT have the blue fan fail relay. Check that both fans work, rotate in the correct direction and the fans are not loose on the shafts. Nothing is obstructing the air inlet to the radiator (a license plate maybe?) Replace the plastic header bottle with a metal tank. If you have ANY leaks you will eventually have air in the system again so NO LEAKS! Check the rad for green staining and the weep hole on the bottom of the neck of the water pump. If you are still adding coolant you have leaks under the intake manifold.

[PB Co]

With the metal versions, there are square ends on the tank. Comparing to the rounded plastic shape you have to wonder if this makes lower coolant levels even more critical on the stainless and aluminum variations on inclines. I cannot visualize how the coolant behaves at temp/pressure but isn't the shape of the plastic container superior? The hemisphere ends would allow for less coolant to maintain a higher level in the tank itself.

[Some guy]

So i looked at the radiator cap. (It came with the car) it is a 16 psi cap, but the o ring on top has some dry rot. the reserve tank was almost empty.

I think this might be one of my issues.

How full are your coolant tanks?

I will stop today and get a 15 psi cap, but 16 psi better? It is a big difference?

[David T]

So i looked at the radiator cap. (It came with the car) it is a 16 psi cap, but the o ring on top has some dry rot. the reserve tank was almost empty.

I think this might be one of my issues.

How full are your coolant tanks?

I will stop today and get a 15 psi cap, but 16 psi better? It is a big difference?

Try to use a 15 psi cap. The header bottle needs to be 1/2 full when cold on level ground. If you have to keep adding to it to keep it 1/2 full you have leaks and then you get air and once the air gets into the water pump the car overheats.