Cooling system won't build pressure.

2TH4IST

2TH4IST

Member
Good morning all. So here is the issue I am having. The cooling system won't build any pressure. Or very little pressure (maybe 5psi or less), zero coolant loss after recent fix and no bubbling.

When I bought the car over a year ago it was neglected. But I went through it and replaced ALL cooling hoses with oem, oem tstat @6 o'clock, oem radiator, oem cap, aisin water pump. This weekend I fixed a coolant leak I had in the intake manifold (happened last week). Also been through 3 rad caps. 2 oem and 1 aftermarket.

The 1st oem cap wouldn't seal up in the pressure tester, the 2nd aftermarket cap sealed really slowly but not reliably, 3rd oem sealed but had to pump the tester really fast, but was reliable.

I refilled with a vacuum filler, then used a pressure tester to test for leaks, it held 15 psi for 30 mins. So good there. Burped it with the coolant funnel, tstat opened and fan engaged, heat in the rear and heat up front.

I'm guessing the cap is faulty again or just not sealing correctly (the small little giggle valve). System builds up pressure with pressure tester on rad. Zero coolant leaks now. Coolant temps are between 191-197 degrees, not overheating.

Only remedy I see is to install a koyo rad with a cs cap to eliminate this stupid giggle valve thingy. Unless the oem rad I have is defective, then a replacement is needed and would go the koyo route anyways.

Is there any other area I should inspect or test? Or I'm just thinking about this to much lol. Every vehicle I have owned and worked on built up pressure. Thanks all.
 
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2TH4IST said:
...cooling system won't build any pressure. Or very little pressure (maybe 5psi or less)...

refilled with a vacuum filler, then used a pressure tester to test for leaks, it held 15 psi for 30 mins....

Coolant temps are between 191-197 degrees, not overheating....
Click to expand...

The first statement doesn't make sense if engine got up to 197 during pressure test.

But if not overheating, not leaking, not loosing coolant, I'd leave it alone but keep at least one eye on it.....
 
Sorry it didn't get to 197 with pressure tester (the pump type of pressure tester), just turning the engine on and idling for about 5 mins got the psi to over 15 and maybe 120 degrees. Removed pressure tester as it was climbing higher then 15 psi and I didn't want to blow the radiator or hoses up.

Did a test drive and engine hit 197, poped the hood and no pressure built up (squeezing the hose, hearing the coolant moving back and forth from expansion tank to rad). Drive it home still between 191 and 197 and rechecked and a tiny bit of pressure was built up.

Tstat is opening like normal, new aisin fan clutch too, and works good.
 
2TH4IST said:
Sorry it didn't get to 197 with pressure tester (the pump type of pressure tester), just turning the engine on and idling for about 5 mins got the psi to over 15 and maybe 120 degrees. Removed pressure tester as it was climbing higher then 15 psi and I didn't want to blow the radiator or hoses up.

Did a test drive and engine hit 197, poped the hood and no pressure built up (squeezing the hose, hearing the coolant moving back and forth from expansion tank to rad). Drive it home still between 191 and 197 and rechecked and a tiny bit of pressure was built up.

Tstat is opening like normal, new aisin fan clutch too, and works good.
Click to expand...

That to me would indicate either the radiator cap or the radiator flange for the radiator cap is the culprit. If it were me I would lean towards it being the radiator.
 
Should be easy enough to look in the radiator neck at the sealing surface and inspect it for damage/defects.
Maybe rub a finger around it. Can feel stuff we can’t see.
Cool radiator a given.
 
so about 2 years ago I did a new Denso radiator...and timing belt etc...all asin kit. also replaced top and bottom hose with toyota hoses. Kept having issues with fluid loss at top of radiator. thought it was the hose connection from top hose or to expansion tank.Kept checking and replaced clamps. Top of radiator would have crusty pink stuff on top of radiator. Would clean it , a few days later it was back. I had read about problems with crimping...so out of frustration I took a flat head screwdriver and a small hammer and punched down all the crimp fittings of radiator to top expansion tank. Of course could not tell if I was doing anything...small changes if any.

End of problem.

maybe just a coincidence to other stuff I was tightening etc
 
I have no coolant loss or pink fuzzys, I'm letting the car cool and I'll check the cap seat on the rad. That might be the issue I have.
 
Very common for radiator caps to have issues and be bad.

Any crustys on the radiators are pressure leaks.


Verify your hoses are snug as your pressure is bleeding off somewhere in the cooling system.



Sent from my SM-J337V using Tapatalk
 
No coolant leaks what so ever. I have bee through 3 new rad caps already, 2 oem 1 aftermarket. Holds 15 psi for over 30 mins with my pump type pressure tester.
 
2TH4IST said:
No coolant leaks what so ever. I have bee through 3 new rad caps already, 2 oem 1 aftermarket. Holds 15 psi for over 30 mins with my pump type pressure tester.
Click to expand...

So its holding pressure for over 30 mins with the pump. That leaves the cap or the seal area in the radiator not letting it seal. What else is could it it be if the pump seal is sealing it for 30 mins?
 
Yep it's the radiator. No damage on the sealing surface, just a bit to much height on the radiator neck. Bummer. But just going to upgrade to the koyo rad anyways.
 
Yeah found it when I put the cap on the cap tester, was super tight, on the rad I could turn the cap with one finger. Measure it out and it's quite a bit difference (can't remember the exact measurements). This sucks for me as I've had this rad a bit over a year so I'm just out of warranty. Boo.
 
2TH4IST said:
Yeah found it when I put the cap on the cap tester, was super tight, on the rad I could turn the cap with one finger. Measure it out and it's quite a bit difference (can't remember the exact measurements). This sucks for me as I've had this rad a bit over a year so I'm just out of warranty. Boo.
Click to expand...
Ouch! I'm glad you found it though
 
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