Hey guys,

I did a search, and didn't really find anything about my problem. I just put in a new AST and fluidyne radiator, replaced some heater hoses and the radiator upper and lower hose. Pressure tested it, I had some leaks, tightened down the clamps and thought everything should be ok. So i drove it around, and decided to try pressure testing it again the next day after the car's completely cooled to double check everything.

This is where i ran into a weird problem, the first two times I pressure tested it this morning, i pumped it up to 13psi, and it lost pressure, down to around 10-11 psi and stayed there within 5 minutes. That seemed kind of weird to me because it wasn't doing this before, i did it again and went out to lunch. When i came back, same thing. I checked underneath the car, no puddles, I did a quick search on these forums and checked inside the cabin, no wet carpet so i don't think its the heater core. I did it a 3rd time, and left it pressurized for around an hour while i did some more searching, I came back and it was holding pressure at 13 psi.

Anybody have any input as to what it could be? I don't know why it was losing pressure in the first place, and i'm scared to drive it around when there could be a coolant problem. Thanks in advance!

 

You're right to be scared to drive it. You need to figure out where it is leaking.

Did it ever overheat? Was it losing coolant and pressure before your radiator install?

Did you try pressure testing with the car on stands or a lift, so you can see where the coolant is coming from.

Maybe your pressure cap isn't sealing on the AST lip properly or is malfunctioning. Are you testing from the fill cap or AST/pressure cap location?

 

did it get hot? is the coolant low?

 

Nope, It never overheated, I'm using the stock water temp gauge though, so I'm not sure what the actual temps are. i'm just watching that thing like a hawk when I take it around to test it out. I'm not sure if It was losing pressure before, I bought the car recently, and started doing some reliability mods, I never pressure tested it with the stock set up, I didn't see any puddles when it was just parked in my garage though.

This time when i tested it, it was just parked in the garage, I've done it before when it was on stands so i was able to chase down some leaks and fix them up until i got to this problem. I was looking for some puddles on the ground, which confused me because i saw none, but i was losing pressure. I'm not too sure as to why the last time i did it I wasn't.

Maybe that's it, I was pressure testing it from the AST location, the tester i borrowed from autozone didn't have the adapter to make it fit the filler neck area.

 

I drove it around yesterday after putting everything together, this morning when i took off the filler cap, the coolant was full, I'll check again tonight after the car cools down.

 

Ok, make sure the tester is sealing properly on the AST neck.

Did you burp/bleed the coolant system when you refilled it? You get a funnel that fits tightly (makes a decent seal, yellow spill saver brand works for me) in the filler neck and idle the engine up to temp.

Keep a little coolant in the funnel as it warms up. If you've just refilled the coolant after a drain it's going to release alot of air so keep an eye on the level in the funnel.

It almost sounds like the tester isn't sealing or the hose between the cap fitting and the pump/tester is leaking. Reason I say that is because a coolant leak usually creates repeatable results.

 

When i filled it, i followed the directions i found on this forum, I disconnected the hose that runs right alongside the firewall and filled it until fluid started coming out, then reconnected.

I think there's still air in the system though, I figured i could just drive it around a couple times and top it off every night. Do you think this would be enough to get rid of the bubbles?

Hopefully it turns out to be a faulty tester, do you know of any other place that the coolant could be leaking to? I checked the oil dip stick and it didn't seem to have any coolant in there.

 

i think it was a faulty tester, drove it around a few more times, let it cool down, checked the filler neck and it wasn't low at all. No drips beneath the engine bay either, hopefully this is the last time I need to worry about it, thanks for all your guy's help!