HELP! bubbles in coolant, not HG, not CAP, no leaks..

[boycelaforest707]

I'm posting this on my friends' account:

this problem is still occuring and still unanswered.

Firstoff, I have a Koyo radiator, FAL-210 Fans, OEM Replacement waterpump, newly replaced thermostat (when engine was rebuilt 5k miles ago).

I have no visible leaks, and I think the only loss of coolant occurs when I mess w/ the system to observe and release teh bubbles.

I have bubbles in my coolant that build up. I bought a radiator cap with a release switch so that I can easily let out the bubbles. For some reason the bubbles do NOT come out of the system on its own...

I had the bubbles tested for hydrocarbons, there is absolutely NONE. Headgasket is fine, then. ---------------------------------------------- The problem is, if I do not release the buildup of bubbles for about 8 days, enough build up that they (i'm guessing) begin to affect the system, build up against the thermostat and cause Airlock... Then I overheat. I just pull over, release the bubbles, system goes back to normal and I drive on.

I also get these bubbles when Idling.. I get more when the engine is driven, but I do still get them when idling...

There are some fixes I have considered: 1) Drill hole in thermostat so the airlock cannot occur. 2) Drill hole in radiator cap seal to allow the bubbles to flow into the overflow --- The problem with these 'workarounds' is that they DO NOT FIX THE BUBBLES, THEY JUST MAKE IT WORK WITH IT. And also, when I do turbo my KADE this spring, I'm sure it'll be important for the coolant system to be pressurized and not openly flowing into the reservoir...

I dont think it is cavitation because it happens even during idle and I have an OEM replacement waterpump I am pretty damn sure now it is not the HG. And 3 radiator caps later, I have a feeling it is not the radiator cap.

CAN SOMEONE HELP? Would there be any kind of specialist who could diagnose the problem and fix it?

[hannibal]

240's are notorious for being difficult to bleed the air out of the cooling system. Try following the procedure in the FSM with the car parked on a hill (fron end pointing uphill).

[Turbon8er]

Check the front of the intake manifold on top where the coolant hose connects... there should be an air bleed bolt (8mm, w/ a small copper washer). With the car running, remove the bolt and watch the air bubbles run out until there is only steady coolant (usually within a minute or so), then replace the bolt. Being that the radiator is slightly lower than the engine, this is the prime spot for air evacuation.

You may do it at idle, but i had such erratic idle that i held the throttle open (steady) around 2k while doing mine. i haven't had a problem since. If you must rev it, be sure not to let it suck air back into the system before replacing the bolt.

Also check (or just replace for good measure) your Coolant temp sensor, mine was bad.

Hope this helps you out

[boycelaforest707]

I guess i forgot to mention that I know how to bleed the system of bubbles...

these are not 'trapped' bubbles.. these are bubbles that FORM or are NEW to the system. They only air that is in the system comes from these bubbles and it builds up enough to cause airlock if I don't bleed it out within about 8 days of normal driving.

[Turbon8er]

that's nuts... i've really scratched my head on this one. I know it sounds corny.. but is your mixture right? too much water evaporation, maybe?? or a 'lemon' thermostat that wouldn't open properly and let the system vent out hot coolant? or even the absolute slightest fraction of a possibility that there is a fracture in the intake manifold itself letting air from runner #1 seep into the flow... err maybe? or the intake manifold gasket not seating properly against the head enabling air to slip by from the runner to port area, might be more of a possibility?

i hope you get it figured out.... sounds effing frustrating