I’ve been having a cooling issue since I replaced the head gasket and new head. It heats up while driving, upper rad hose is hot lower is cold along with the rad, then rapidly cools in a few seconds, 230 to 199 in just a few seconds when stopped or when under 2k rpms
replaced the tstat, radiator, temp sensor and did a vacuum on the cooling system. It can keep cool if you keep it under 2k rpm.
im at a loss here.
haven't done the water pump yet but im getting hot air.
no leaks, no smoke no milky oil.
Am I fighting an air lock?

 

Sounds like to me a faulty t stat. Hot up top and cold down low means that the t stat is not opening. What temp and brand did you get?

 

it’s a 180f and it’s one from OReiles
not failsafe.

 

My bet would be on that. I have had bad ones straight from the box before. I am not sure on if you can test it this way or not, but on other cars you can remove it and test it and see if that solves the issue. Im sure someone will chime in.

 

ill run it with out the tstat, I’ll gut the old tstat so it’s just the outer ring. Well see what happens, thank you!!

 

I was once told to only use the OEM tstat, as this is what happens. I tried using the other brands but had the same issue as you. Switched back and no more problems. Maybe try an OEM and see what happens?

 

where does one fine OEM? Dealer?

 

Yeah. I paid a little more for it (not an arm and leg or anything, just a few bucks). I think they're AC Delco brand.

 

You can get the a/c delco brand from rock auto. That's where I get my parts from. The other thing you want to watch for is constant air bubbles in your overflow, you did the headgasket but there's a chance the head could have a crack and allowing compression to slowly push into the cooling system. T stat won't open for air. The cooling system is considered a "open" cooling system and they pretty much self bleed unlike cars with a conventional cap on the rad, so having heat really won't tell you much

 

Best way I have found to purge air from the system is connect a hose to the nipple by the upper radiator hose which normally goes to the expansion tank. Fill the funnel with fluid and raise it up high to create pressure.



I agree that some things are important to use OEM but t-stats are pretty basic. You can test the thermostat before installing by placing in boiling water on the stove.

 

ive had a block test done and it’s past, we’ve put vacuum on the cooling system and it held 15psi For an hour. I’m just not getting flow I’m about to put in a gutted tstat and see what happens

 

I'd personally just skip the gutted t-stat; changing the way the system flows can create it's own unique problems.

Put the thermostat in a pot of water and slowly bring it to a boil; you're checking to make sure it opens up properly. If you have a thermometer that you can put in the water with it, that'd be superb.

Or skip all of that and just get yourself a stock thermostat to put in there. I think I have an LNF thermostat just sitting in my garage - I'd need to check; I'll send it to you for the price of shipping.

ZZP sells them for $20: https://zzperformance.com/collection...tec-thermostat

 

Are the hoses hard once the car warms up? If you have soft hoses that may indicate water pump issue. The fins may have rotted off the impeller

 

top is hard bottom is cold along with the rad. The bottom is hard too but cold

 

The hoses get hard from the system pressurizing due to heat, not the differential pressure from the water pump.

 

should I get a new water pump? Everything else is been changed but the water pump

 

The fact that it cools down as rapidly as you've said it does leads me to believe it's just your thermostat opening late.

I've had bad water pumps in other cars... they struggle to get the fluid flowing, and therefore struggle to get things cool at all.

 

First thing is to do the funnel trick to make sure you don't have an air pocket. Second would be to verify your thermostat is functioning correctly, .

Did you replace your radiator as an attempt to correct this issue or did you replace it for other reasons? The issue you are experiencing is likely from something that happened while you were working on it, whether it was a bad new part or a mishap. Think of anything you did that could affect the cooling system. Did you replace the head gasket yourself? There's a chance something happened to your BS/Water-pump chain when you had the timing cover off. I really doubt your water pump suddenly failed if it was working before you replaced the head gasket.

Another possibility is you still have an issue with the HG sealing. If you replaced the head it sounds like your HG failure must have caused significant damage to your original head? You can have head gasket issues that won't always be detected by a pressure/vacuum test of the cooling system. Find out if someone in your area has one of those combustion gas test kits that test a sample of your coolant for combustion contamination.