JDM EJ20Y Coolant problem when in high turbo boost

Hello guys;

 

I have a 2008 subaru legacy which had a EJ204 engine on it, i swapped the engine, transmission and differential of a JDM EJ20Y engine with it, my car once got overheated although the temperature gauge did not reach the redline but almost most of the coolant was gone because of a lose hose. Now i have a problem which is the level of coolant gets lower without a leak, the car starts perfectly, no abnormal vibration or sound, no white smoke, no milky water in the radiator and there is no indication of water in engine oil, no bubbles in the radiator, yet when the turbo is in high boost when the radiator cap is off it spits almost 50 cm of coolant. ONLY when the turbo boost is high, what do you think guys? You think the Head gasket has blown? Or you think there is a leak in the cooling circuit? Does anyone have the diagram of EJ20Y cooling system?

The coolant system is a pressurized system, so when you run high rpm with the cap off... that could happen. Are you sure you got the air out of the system? It's not uncommon for some air to work its way out and lower the coolant in the expansion tank over time. If you're sure, you must have a leak somewhere; no sweet smell?

Yes, i have got the air out and bleed the system, there is no sweet smell, the amount of water drops in a short amount of time. Is it common and normal for the coolant to spit out when the radiator cap is off when the boost is high?

I guess what we're asking is why are you in a situation where you're under boost with your radiator cap off?

This is one of the questions i have, the other question is why does the level of water or coolant is droping when there is no external leak, no sign of sweet smell, no sign of water mixed in the oil, no milky coolant in the radiator, no bubbles, engine starts perfect it runs perfectly, no white smoke, i have a doubt that it might be the HG. And yes i am wondering why the coolant is spitting out when under boost, the spit is pretty strong about 50-60 cm. You see when the car is either cold or warm, when the engine goes to high RPM, if the cap is off it spits out the coolant but when the cap is on the coolant goes to expansion tank and it gets overfilled and the coolant out of expansion tank does not return to the radiator Edited June 6, 2020 by Amir

Lets ignore the coolant shooting out of the radiator for this one; the cooling system is a pressurized system. Every radiator may do this when you hit boost with the cap off; i don't know, I've never tried it, I don't know why you would.

 

Regarding your cooling problem, i'm hearing two different things:

 

1. the coolant level drops. I assume it's dropping from the expansion tank? Is this correct?

 

2. with the cap on, the coolant runs into the expansion tank and overflows. Also correct?

 

These two statements seem to contradict one another, and ultimately make it difficult to diagnose your problem. By chance, is the coolant draining from the expansion tank as the vehicle cools and overflows when its hot? Are you adding coolant when it runs out over and over?

Yes, the coolant level drops, in my opinion i say it is droping from the expansion tank, but it might be from the HG, I still don't know it yet. There is absolutely no sign of damaged HG, and the answer to the second question is yes, it goes into the expansion tank and overflows. When the engine is hot it overflows from the expansion tank. I am adding coolant since the level drops. I was reading what you send here at the beginning, can u give me a post where i can do the system bleeding correctly for this engine? Let me do the bleeding once more in a correct way and i will check it again. I need the step by step procedure to do the bleeding correctly. Many thanks.

If the level got that low, have you rebled the air out of the system with the heater on high ?

 

We jack up the right front corner of the car as high as we can, remove the turbo tank cap and start the engine with heater On. Watch for air bubble in that tank while the engine is at idle.

 

I also don't understand why anyone would go to high boost without the caps in place.

I'll try bleeding it and will let you know.

Please do, we'll be interested to hear the results.

Hi guys, thanks a lot for the suggestion, the car is working much better now and also found out that my radiator cap was not functioning well, i changed it and it's ok now. Thanks a lot.