1998 4.0 Gems Range Rover SE

I have been fighting this cooling system for months. Have replaced...
Radiator, water pump, thermostat. Heater core. Cap.

Throttle plate cooler bypassed.

System holds vacuum with Airlift fill tool.

I drained it and refilled it again today. Airlift doesn’t work so hot unless it’s empty.

hose from top of rad to expansion tank is clear.

Today I sealed a big funnel to the expansion tank. The coolant was highest point.

I ran it for probably two hours today. I did a bunch of test with the blue fluid and at no point were the gases coming out making it yellow. I put a scope down the right cylinder bank and none looked steam cleaned. Spark plugs look great. Not wet.

In my hours of messing with it today I reached an equilibrium where the situation stopped changing. So I have had it running for hours. Its warm and has been warm. Heat blowing hot full blast inside. Both heater hoses for the matrix are hot. Seems to be flowing like a champ. I got my coolant level up out of the expansion tank and just barely up into the funnel, bottom of funnel cup. I jump in the drivers seat and blip it up to 2k RPM for 3 seconds. Typically this would cause a violent coolant eruption from the expansion tank, but not with the funnel on there. Now it fills the funnel cup. If I revved it up long it will overflow the funnel. After a few seconds it bubbles back down to the funnel neck. Back to down to the level before I revved it, no change.

rev, bubble down, rev, bubble down, rev, bubble down. I swear this could go on all day and it won’t overheat. If I put the cap on and rev (or drive), the top hose will get tighter than a nuns pus and it will eventually explode the heater matrix, again.

Is it safe to say head gasket at this point? It certainly seams like bubbles for hours with no level change could only be exhaust gas.

 

It could simply be that the relief valve on the expansion tank cap is not functioning. IIRC it is rated at 15 psi. For $10-15 it s worth a shot.

 

The cap is not part of my scenario above. But I have put the cap on previous with the tank empty and given the tank pressure with shop air. Cap pops at 15psi every time. Its not the cap.

Continuous bubbles for hours. Bubbles that don’t change the level have to be coming from somewhere. System holds vacuum so it must be picking up new bubbles from inside. Exhaust is the only explanation I can wrap my mind around.

 

Here is a video. Note: I revved and let it bubble down probably 20 times. Only videoed once.

 

Have you drained the entire system and blown out all coolant, then carefully measured the amount of coolant put in?
That would give you a baseline on whether you have an air pocket in your system, though the fact you reved and burped the system so many times leans toward your system pulling in air.

 

It holds more than 25 lbs of vacuum forever.

 

Try holding it at 2k for 60 seconds. That should blow out any bubbles that are hiding in the system. Let us know how that goes.