Yet another coolant leak (Page 2/5)
buddycraigg NOV 04, 08:46 PM

quote
Originally posted by Cliff Pennock:

It might very well be the cap. I had replaced it some time ago and one thing I immediately noticed about this cap was that it hardly took any effort to close it. My old cap took considerable effort to close.



I use oil filter plyers to take off the cap.
I don't remember ever being able to take one off with my bare hands.

NEXT QUESTION
Do you have access to an air compressor?

Drain the pressure off until it is about 16-17-ish PSI.
Fill your cooling system full of liquid.
Use the air to pressurize the system by putting it in the over flow tank nozzle on the radiator.
Now you can look for leaks while everything is cold.

[This message has been edited by buddycraigg (edited 11-04-2023).]

Patrick NOV 04, 08:52 PM

quote
Originally posted by Cliff Pennock:

It might very well be the cap. I had replaced it some time ago and one thing I immediately noticed about this cap was that it hardly took any effort to close it. My old cap took considerable effort to close.



That might've been because some of the older caps had rubber seals that had to turn with the cap... whereas with the newer style, the cap can rotate independently of the rubber seal. That makes a huge difference with the amount of torque required to turn the cap when it's tight.

Doesn't matter how good the cap's rubber seal is if the sealing edge of the metal thermostat housing is corroded/pitted. You need to use a flat sanding block to sand that metal sealing edge so that a nice shiny continuous circle appears at the top of the housing.

[This message has been edited by Patrick (edited 11-06-2023).]

Cliff Pennock NOV 05, 11:09 AM
I was able to check it a bit better and it's definitely leaking from the cap. I have another cap laying around somewhere, so I'll check if that makes a difference. If not, I'll sand down the sealing edge.
sleek fiero NOV 05, 12:13 PM
Hi Cliff;
Sanding the sealing surface is not advised as you will remove the rust preventive plating which would allow corrosion to start. Certainly check lip for damage and precede accordingly . Mine got some damage where the rad hose clamped on probably from prying the hose off at one time and eventually corroded through. sleek
Patrick NOV 05, 05:05 PM

quote
Originally posted by sleek fiero:

Sanding the sealing surface is not advised as you will remove the rust preventive plating which would allow corrosion to start.



If the top of the thermostat housing has been even slightly bent or misshapen (due to manhandling the cap to get it on or off), then it's not going to seal properly.

By using a flat sanding block (not just a loose piece of fine-grit sandpaper), it can quickly and easily be determined if the sealing edge of the thermostat housing is both flat and non-pitted.

In regards to any "rust preventive plating" being removed, keep in mind that any metal removed by a flat sanding block is going to be protected by the rubber seal of the cap when it's installed. Coolant won't be able to access the polished lip.

[This message has been edited by Patrick (edited 11-05-2023).]

Cliff Pennock NOV 06, 07:36 AM
I found my old cap and I wasn't even able to put it on. I couldn't get enough downwards force on it for the lips to catch the lips on the housing. Compare that to the new cap which closes without any effort whatsoever. So I compared the two caps and the new cap is much higher than the old (original) cap. This tells me the new cap simply doesn't seal properly.

Now the thermostat itself doesn't "click" in place. It just "floats" and is held down by the cap. This might also be the reason why I can't get the original cap to close since the thermostat might not be far enough down the housing.
82-T/A [At Work] NOV 06, 07:47 AM

quote
Originally posted by Cliff Pennock:

I found my old cap and I wasn't even able to put it on. I couldn't get enough downwards force on it for the lips to catch the lips on the housing. Compare that to the new cap which closes without any effort whatsoever. So I compared the two caps and the new cap is much higher than the old (original) cap. This tells me the new cap simply doesn't seal properly.

Now the thermostat itself doesn't "click" in place. It just "floats" and is held down by the cap. This might also be the reason why I can't get the original cap to close since the thermostat might not be far enough down the housing.




I've you've not changed it in a while, it can't hurt to swap out the thermostat with a new one. It's isolated by a rubber O-RING that can sometimes slip off. But it should be a snug fit. Is it possible that the thermostat is not the right one?
Cliff Pennock NOV 06, 07:56 AM
I have three thermostats here. Two 195*, and one 180*. I can't remember which one is the original but I will try a different thermostat (as soon as the engine has cooled off - had to run some errands).
Spadesluck NOV 06, 09:52 AM

quote
Originally posted by Cliff Pennock:

I have three thermostats here. Two 195*, and one 180*. I can't remember which one is the original but I will try a different thermostat (as soon as the engine has cooled off - had to run some errands).



195 should be the original.
Cliff Pennock NOV 06, 12:20 PM
I put in the "old" 195* thermostat and I still wasn't able to close the housing with the old cap. Also, I think this thermostat is stuck open since it took a really, really long time for the car to reach operating temperature (almost 10 miles). I think I'll order a new cap and thermostat.