Cooling System Pressure Test Procedure

[mwesten]

All - what?s the correct process (steps in order if you don?t mind) to pressure test the cooling system? Where I?m at now specifically is I?ve put in all new hoses, radiator, y pipe and seals and the water pump is next up, so I?m close to testing. Given all that, the system is prob 90% void of coolant and since I can?t actually start the car yet how (or should I even) get coolant/water into all the nooks and crannies of the system? Do I test ?dry? and if it holds 15psi for a while put the valley back together? Or do I pour as much coolant as I can into the bottle and t-stat as I can then test?

[David T]

All - what?s the correct process (steps in order if you don?t mind) to pressure test the cooling system? Where I?m at now specifically is I?ve put in all new hoses, radiator, y pipe and seals and the water pump is next up, so I?m close to testing. Given all that, the system is prob 90% void of coolant and since I can?t actually start the car yet how (or should I even) get coolant/water into all the nooks and crannies of the system? Do I test ?dry? and if it holds 15psi for a while put the valley back together? Or do I pour as much coolant as I can into the bottle and t-stat as I can then test?


You fill the coolant system with 50/50 anti-freeze (the good ole green stuff aka Prestone is fine) and soft water. Fill it up and then hook up the tester. Pressurize to about 5 psi and look for any large leaks. If it holds go to about 10 psi. If that holds then open the bleeder by the thermostat to let out the air. Represurize back to 10 psi and loosen the small hose on the top, right side of the radiator and let the air out. If no leaks go to 12 psi and watch for any drop in pressure or leaks. If all is good slowly release the pressure and make sure the header tank is at least 1/2 full. Test the pressure cap and you're done. When you drive the car for a few cycles recheck the level in the header tank.

[mwesten]

You fill the coolant system with 50/50 anti-freeze (the good ole green stuff aka Prestone is fine) and soft water. Fill it up and then hook up the tester. Pressurize to about 5 psi and look for any large leaks. If it holds go to about 10 psi. If that holds then open the bleeder by the thermostat to let out the air. Represurize back to 10 psi and loosen the small hose on the top, right side of the radiator and let the air out. If no leaks go to 12 psi and watch for any drop in pressure or leaks. If all is good slowly release the pressure and make sure the header tank is at least 1/2 full. Test the pressure cap and you're done. When you drive the car for a few cycles recheck the level in the header tank.

Awesome thanks DT. To clarify, are you saying it?s ok that the entire system isn?t full of coolant? Seems like there?s no way to really fill the whole system with fluid until it?s running.

[82DMC12]

Awesome thanks DT. To clarify, are you saying it?s ok that the entire system isn?t full of coolant? Seems like there?s no way to really fill the whole system with fluid until it?s running.

Well if you let all the air out like he said, coolant will fill the whole system (virtually) by gravity. You should of course run the engine to hot and then let it cool overnight and check the expansion tank again. It should be half full. Any higher and it will probably burp some out every time you get the engine hot again until it gets to halfway on its own. Messy.

[Rich]

Awesome thanks DT. To clarify, are you saying it?s ok that the entire system isn?t full of coolant? Seems like there?s no way to really fill the whole system with fluid until it?s running.

No need to heat up the system to start with. You can bleed and then chase leaks with it cold.

David covers the fill, bleed, test procedure. Andy confirms the bleed process, done correctly, does fill the whole system. As mentioned the two places to bleed are at the thermostat housing (helps to have a section of clear vinyl tubing pressed over the bleed nipple and leading to a bucket below to minimize the messiness) and the upper right bleed hose on the radiator (wrap some old towels or rags below the nipple when you pull off that hose - you need to bleed both the hose end and the radiator nipple there before reconnecting the hose).

Also as mentioned the filling and bleeding can be done by gravity. The car can be level, no need to lift the front end but if you don't have a level work area then its best that the highest wheel is the right front so the rad will bleed all the way across the top.

Since you did a complete hose replacement job you know where all the new hose connections are. Use a good light plus a mirror to look them all over when pressurized or just feel beneath each of them for signs of coolant after you pressurize, assuming you don't get a steady pressure reading to begin with. As you probably plan, pay extra attention first to the hoses you won't see later on, the ones underneath and behind the intake manifold.

Be patient - small leaks take time to show up during a pressure test. You don't want to discover a leak later, especially under the intake manifold or above the bell housing.

Final notes - if you installed any silicone hoses expect to find a few leaks later on after some heat cycling unless you already tightened those hose clamps enough. An issue with either new rubber or silicone hoses is "new" leaks due to deteriorated coolant pipe nipples. Sometimes the outer surface pitting of old aluminum OE pipes makes it hard to get a good seal against a new hose. Replacement of the pipe may be called for if tighter clamping won't do.

When you're done don't settle for any leaks no matter how small.

[mwesten]

Perfect thanks for the details guys, super helpful. I also have a bleeder kit to install in the back, might get one for the front too.

[David T]

Perfect thanks for the details guys, super helpful. I also have a bleeder kit to install in the back, might get one for the front too.

A Delorean, properly bled, with NO leaks,does not require a bleeder kit. Silicone hoses with the correct style clamps should not need retightening. Good for the hoses under the manifold. All the others can be retightened after a few heat cycles. The cooling system is self-bleeding for a small amount of air, that's one reason why you always want to have the header tank no less than 1/2 full when cold.

[mwesten]

Ok gang some weirdness. New pump, new back, new bolts. Paper gasket coated thinly on both sides with Permatex Water Pump and Thermostat. Pressure testing good everywhere, but noticing dampness and small droplets along parts of the gasket edging. To be clear, I coated the gasket on the SIDES, not the edges. Still, I don?t understand how any coolant is getting through. Also I have the pump back bolts at 10 ft lbs. Any ideas?

[82DMC12]

Ok gang some weirdness. New pump, new back, new bolts. Paper gasket coated thinly on both sides with Permatex Water Pump and Thermostat. Pressure testing good everywhere, but noticing dampness and small droplets along parts of the gasket edging. To be clear, I coated the gasket on the SIDES, not the edges. Still, I don?t understand how any coolant is getting through. Also I have the pump back bolts at 10 ft lbs. Any ideas?

10 ft lbs sounds low. Those M7 bolts, I would bump it up to 14 ft lbs. If that doesn't fix it, the mating surfaces must not have been true enough.

[mwesten]

10 ft lbs sounds low. Those M7 bolts, I would bump it up to 14 ft lbs. If that doesn't fix it, the mating surfaces must not have been true enough.

Ok will give that a go. Crazy this is even an issue with all new parts. Really dont want to have to drain and take the whole thing apart again.

[Rich]

Darn.
The good news is you found the leak before the intake/injection was put back on.

[mwesten]

Darn.
The good news is you found the leak before the intake/injection was put back on.

Agree. Going to tighten the bolts tonight.

Here?s what I dont get? if the gasket is paper, it naturally absorbs liquid so, is it ?normal? for lack of better terms for the rim of the gasket (the sliver that you can see on the outside once installed) to be damp at all?

[WHO1DMC]

Agree. Going to tighten the bolts tonight.

Here?s what I dont get? if the gasket is paper, it naturally absorbs liquid so, is it ?normal? for lack of better terms for the rim of the gasket (the sliver that you can see on the outside once installed) to be damp at all?


I would say If there was a little imperfection it would be normal at first until the paper gasket started doing it's job.

Back in the day it was very common place to soak the paper gasket in water or oil, depending on the application.
This became less and less as parts became better machined and more advanced sealants being developed.




Dave B.

[mwesten]

I would say If there was a little imperfection it would be normal at first until the paper gasket started doing it's job.

Back in the day it was very common place to soak the paper gasket in water or oil, depending on the application.
This became less and less as parts became better machined and more advanced sealants being developed.




Dave B.

Interesting. Seems like by now we would have a silicone water pump gasket.

[mwesten]

I’ll just keep adding on here in the hopes this eventually helps others down the road too. Anyway, heres what I mean. First pic hopefully you can see what Im talking about. Not major leakage, just wet looking crusty spots that have no biz being on all-new parts. Edge of gasket is damp as well.

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And heres my other gasket. Should I just use this gasket naked w/o adding anything?

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[mwesten]

I?ll just keep adding on here in the hopes this eventually helps others down the road too. Anyway, heres what I mean. First pic hopefully you can see what Im talking about. Not major leakage, just wet looking crusty spots that have no biz being on all-new parts. Edge of gasket is damp as well.

69862

And heres my other gasket. Should I just use this gasket naked w/o adding anything?

69863

Aaaannd of it came. That was a fun exercise I wasnt dying to experience. Oh well. Anyway, for those who care, Permatex Water Pump & Thermostat is no bueno as a paper gasket dressing. Peeled off like protective film on a new iPhone. Onto Hylomar or Permatex Permashield 85420.

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