Overheating and checking for vaccuum leak

[Steve P.]

Start with a cold motor. Remove the rad. cap and top off your coolant. This is important as sometimes the rad. cap neck can be cracked and if it's not topped off it will be much harder to find.

Next, put a little water on the seal of the pump cap to lubricate it. Install it in place of the rad cap and pump up the system to about 17-18 pounds and watch the gauge. You have to be careful not to twist or torque the hose between the pump and cap head. Sometimes this will leak giving you an inaccurate reading especially if the tester is getting old. 

The gauge should hold at what ever pressure you pump it up to literally for ever. If you see it drop over a few minutes time you have a leak. Start looking for coolant leaking out of the system. It can leak from any point of the entire cooling system. If you see nothing from under the hood, look under the car for coolant dripping. If still nothing check your tail pipes and also you oil dip stick. It's going somewhere...

If you don't see a COLD leak,(Drop in gauge pressure), let the pressure off the system, make sure you are still topped off and start the motor with the tester attached.  Watch the gauge. It should take a few minutes to start building pressure. If it starts building pressure right away or you see it climbing fast, shut down the motor and let off the pressure being careful not to get burned..
If the pressure goes up right away or very quickly, you are filling the cooling system with cylinder pressure. (cracked head or head gasket).

Report back....

[AmadeusCharger500]

Topped off meaing up to the top of the neck?

I need to rent the tester, and hopefully tomorrow I will test it.

[Steve P.]

Topped off meaning up to the top of the neck?

I need to rent the tester, and hopefully tomorrow I will test it.

Yes.. Top of the neck.

A cooling system  pressure tester should be a part of everyones tool box.. They are not expensive and should be part of everyones maintenance kit.

[NHCharger]

I chased an occasional "running hot" problem for years with my 72,318. Went with different plugs, 165º thermostat, new radiator, etc. I finally decided to check my water pump. The fins/vanes were pitted and slightly corroded but spun freely. I decided to install a new pump. Have never had a running hot problem again. The only theory I can come up with is that since the fins/vanes were pitted it might have caused cavitation, where the water gets agitated by the rough surface of the spinning vanes and can cause tiny air bubbles to get into the cooling system causing the motor to run hot.

[Steve P.]

I chased an occasional "running hot" problem for years with my 72,318. Went with different plugs, 165º thermostat, new radiator, etc. I finally decided to check my water pump. The fins/vanes were pitted and slightly corroded but spun freely. I decided to install a new pump. Have never had a running hot problem again. The only theory I can come up with is that since the fins/vanes were pitted it might have caused cavitation, where the water gets agitated by the rough surface of the spinning vanes and can cause tiny air bubbles to get into the cooling system causing the motor to run hot.

I agree. I have also replaced pumps that had next to no blades/vanes left.  One pump I replaced was a rebuilt El'Cheapo someone put on a florists delivery van. Well, the first hot day after winter they had trouble with their big delivery van and had to send the ASTRO in it's place. The astro came to me on a roll back wrecker.. Their C-60 was allready in my second bay....  Needless to say, those two vans never went back to the old mechanic..
By the way, I replaced the entire motor in the Astro. It was cooked.....

[AmadeusCharger500]

16 pounds pressure and 1 good leak sprung from lower rad hose(Yes I wonder why I never saw that). Pressure went down. Only small amount though. Tightened upper clamp and it stopped. It is holding pressure at 16 now.
Can I cross my fingers that this is my cooling problem? Should I stop testing and just drive it?

[Steve P.]

I would continue testing.

Like everything else on a car, you start at A and work your way to Z trying not to skip a step..

[AmadeusCharger500]

Will, do. I will check as you specified with the guage connected and turn on the car.
I am guessing will know pretty soon the results of this test. If pressure goes up immediate there is a problem, if it is gradual then its normal.

[Steve P.]

That is correct. With heat comes expansion. Just don't let it get much over 15, 16.. You will need to bleed off the pressure. I use a thick rag wrapped around the bleed lever so I don't get burned..

If you start it and it pumps up quick and like a bike tire pump, kill it immediately.

[firefighter3931]

Not much to add....Steve is providing good troubleshootng tips ! 

Keep plugging away at it Heath !   




Ron

[Steve P.]

Thanks buddy. With my crappy memory I sometimes wonder if I even know what the hell I am talking about.. 

[AmadeusCharger500]

I hooked it up and ran it for 5 minutes pressure was not going up, so I shut it off before it could get too warm.
Here is a question.
I have an overflow tank. Is this controlled by the radiator cap? The water was filling it up but never has in the past.
I never fill it past half up from top of the fins. Am I not filling it enough?

[firefighter3931]

Heath, it sounds like your rad cap might be weak/old.....i would try replacing it with a new one and see if that helps. The cooling system sounds like it's holding pressure which is a good sign. 


Ron


Ps. I fill the rad up leaving 1in airspace at the top to allow for thermal expansion.

[Steve P.]

Yes the rad. cap allows over pressure to spill to the overflow tank.  Did you check your cap with the tester?? This I may have forgotten to mention.. Sorry.. I told you I have a bad mem--.. What was I saying??

Test your cap. It may be bad.

Here's another thing I see often..  Your overflow tank should either have the hose from the rad. neck going into the bottom or it should be through the top and hose inside going all the way to the bottom..  Check this.

If the coolant in the overflow tank cannot be sucked back into the rad. as it cools you will start the next cycle lower on coolant.  Even some of the aftermarket overflow tanks are NOT set up properly.. We just installed one from Summit on VegasMikes Charger and it DID NOT flow 2 ways to the bottom... In that case, all it is is a puke tank. Even still, I don't know where they were expecting it to vent..   We bought 2 90* elbow fittings and placed one in the bottom and one in the top. We then fed hose from the rad. neck to the BOTTOM fitting and another hose from the top fitting down just below the bumper bracket. This will allow more than 1/2 gallon extra fluid and also keep the rad. level right at the top..

[AmadeusCharger500]

Checked the cap. It seems to hold only 14 lbs. Anything more and it pops back down.

Question on new caps. This says Stant 231 vented. I remember this nagging feeling I always get when buying a new cap. Should it be vented or not? And what does that even mean?