Help! Intake Manifold Gasket or Head Gasket?

Hoping for some expertise and advice (long post, read all for context)

A couple weeks ago I redid the intake manifold gaskets, valve cover gaskets, thermostat, fresh fluid in the radiator etc. If it was there, I did it (minus anything head related)
I didn't have any overheating issues prior to the project, I took things apart to repaint and clean them.

Shortly after reassembling the engine and going for a drive, I parked the car for 10 minutes and came back to the lower rad hose popped off and all my coolant on the ground.
I jacked the front end up, refilled and burped the system and went on my way. The car overheated, I pulled over and added more coolant and that was that.

Fast forward a couple days later and the car overheats again... thermostat got an air bubble and closed. I pulled over cooled it down, went home and burped it and the car was ok for a few days. Now the car will do this "runs fine for a few days, thermostat closes while driving and reads hot, I burp pressure out of the rad, refill coolant, tstat opens, car is ok" routine over and over about 4 times so far.

Ive began noticing a bit more steam than usual in the exhaust while driving, more water dripping while idling, coolant disappearing and overheating... I think headgasket. So I check the classic head gasket tests. Oil: no chocolate milk looks normal. Compression: every cylinder within 10% and at normal pressures (I tested on a ~140* block, all spark plugs removed at the same time). I test for combustion gas leaks in the coolant bubbles: Fluid stays blue and clear.

So now what? It's passing the head gasket tests so far... could it be a leak on the intake manifold gasket putting water into my intake port and into the cylinder? Would a intake manifold gasket cause air in the coolant?

I need advice before I rip the car back apart and get gaskets. I appreciate any help, thanks!

nicholase said:

Did you put the thermo stat in backwards by chance? Sorry for questioning the basic, but it happens.

Also the good thromostats have a jiggle valve. It installs facing up and let's air through as you fill with coolant so you don't get an air pocket behind the t stat.





You said you did a compression test. What did the plugs look like when you had them out? You can Google images of what a plug looks like with a head gasket leak.

How are you "burping" this? It sounds to me like you just have air in there. I've never had to jack the front up or anything. What is your filling procedure?

Usually you can smell a head gasket leak, or if it's burning coolant for some reason. Do you smell it? Coolant has a distinctive smell when it burns either leaking on something hot or out the tail pipe.

I'd make sure you are filling it correctly. Then pressure test the cooling system. You can probably rent the tool if you don't have one.

Edit, also did you remove the EGR cooler? Those gaskets can leak coolant into the throttlebody.

Click to expand...

Brand new thermostat with a jiggle valve, I tested it in the kitchen with boiling water and triple checked it went in the correct direction. (Triangle end towards radiator)

All the spart plugs looked the same, normal with a little brown dust. None were steam cleaned or stood out as different.

I didn't remove the throttle body/ EGR cooler and I dont see leaks, the hoses are back in the right places, and im losing so much coolant that (I think) if it was pumped into the throttle body at this volume the car wouldn't run right or at all.

I re-burped last night with a spill proof funnel and the front jacked up, and followed all normal burping steps.

We tested some more last night and even with the spill proof funnel we couldn't get it to burp. It would bubble then stop. Then overheat then cool down. Then bubble and overheat again like a cycle. The coolant level was surging. When we tested with the combustion leak fluid again it was okay. ...the bubbles in the coolant are air, not combustion gas...

We went round and round but my guess is a few issues
1. Bad thermostat is causing surging, or the air coming in is working its way to the tstat causing a surge and then cycles to a different part of the system.
2. A bad radiator cap is causing the coolant to leave but not re-enter the radiator. (My expansion tank would fill but never go down when the car got to temp
3. Intake manifold gasket leak is between the coolant passage and the intake hole on the head, so as the coolant enters the intake stroke a bit of air from the intake manifold is getting sucked into the coolant to displace the void.

My next step is a coolant system pressure test and a boroscope to check cylinders 1,4,5,8 for a steam clean.

Any other advice or ideas are appreciated thanks.

nicholase said:

Did you put the thermo stat in backwards by chance? Sorry for questioning the basic, but it happens.

Also the good thromostats have a jiggle valve. It installs facing up and let's air through as you fill with coolant so you don't get an air pocket behind the t stat.





You said you did a compression test. What did the plugs look like when you had them out? You can Google images of what a plug looks like with a head gasket leak.

How are you "burping" this? It sounds to me like you just have air in there. I've never had to jack the front up or anything. What is your filling procedure?

Usually you can smell a head gasket leak, or if it's burning coolant for some reason. Do you smell it? Coolant has a distinctive smell when it burns either leaking on something hot or out the tail pipe.

I'd make sure you are filling it correctly. Then pressure test the cooling system. You can probably rent the tool if you don't have one.

Edit, also did you remove the EGR cooler? Those gaskets can leak coolant into the throttlebody.

Click to expand...

.

Update:

I checked cylinders 1,4,5,8 with a boroscope and they were normal and weren't steam-cleaned. (Unnecessary to check cyl 2,3,6,7 they aren't adjacent to an intake hole)

I pressure tested the radiator and it holds a perfect 15psi over 30+ min. I made sure to bump the key and retest it to make sure a valve wasn't closed.

Where in the world is the leak? There's definitely water in the exhaust and definitely air in the coolant.