I am new to evos and new to 4g63's. At my wife's urging we have bought a 2006 evo 9 as it is more practical than the Hondas I used to own, and she likes having a/c.

Here are my symptoms and problems-
- no coolant in oil, no oil in coolant.
- once the cooling system is burped, there doesn't seem to be any bubbling in the coolant reservoir or radiator
- the car hasn't overheated at all when driving.

So after my first 125mi long trip in the car (a/c blasting) I stopped at my inlaws to cool the car down before shutting it off. I was not driving hard what so ever, just a freeway cruise. As it was cooling the temperature began to climb on the gauge. It had been fine up to this point, even at stop lights through town and on the highway. I open the hood to fond the coolant overflow full, bubbling and dumping fluid out the overflow tube. I shut the car down and let it cool a bit, and open the radiator cap finding the fluid to be very low.

The next day I refill with coolant and burp the system, and drive it home. No issues there either, car doesn't over heat when I come to a stop to cool it down at home, either. After cooling I notice again coolant is missing from radiator and that passenger side wheel well has coolant all over it.

I take it up to my shop and warm it up again to do a compression test and cooling system pressure check. At this time I notice while idling there is a coolant puddle forming below the t-belt water pump area. I would assume that the water pump is leaking.

My concern here is that there may be a head gasket issue as well as the water pump leak, when burped properly and full of coolant I do not notice any bubbling in radiator or overflow. Would the system push coolant and displace it with air as it leaks out? I'm sure there is additional info I can provide but I am not sure what else to include. Any help would be appreciated!

 

i should add that the compression test was 150-145-145-150, which according to the FSM is 100% normal / stock.

 

I say chase the leak. Then see.

 

Can be few things in my head...
thermostat, water pump or headgasket. How many milies on yours? Have you replace water pump while doing timing belt service?

 

car has 75,000 miles. t stat doesn't seem to be sticking, no temperature spikes on the highway or at idle with the car burped and full coolant.

i am not sure that the T-Belt, H20 pump and tensioner service has been done, I bought the car a week ago. The fact that I have the very common IX t-belt noice and that the water pump is leaking leads me to believe not, but the belt looks to be in OK condition, although it is impossible to tell without pulling it off.

i am taking the car to english racing to get the waterpump and tbelt done next monday, but i am hoping to know by then whether or not it has a bad head gasket as it will be much cheaper to do the HG at the same time as the other stuff.

thanks for the input.

edit: also going to replace the rad cap with another 1.1 bar one, because it can't hurt and it's cheap.

 

So is this happening when you're just cruising around or are you getting into boost? The overflow filling up means the system is getting pressurized and pushing coolant.

Problem is a compression test doesn't indicate if the head has lifted under boost. You can buy test kits that check for combustion gases in the coolant and that should give you a pretty definitive answer.

Either way, you should have the head gasket and studs done while its there for the timing belt job.

 

+1^

 

As stated it IS NOT happening when I am cruising around or getting into boost. It only happens after a very long trip when coolant has already leaked out of the car a bit, presumably from my water pump leak. The car hasn't over heated or pushed coolant on short around town trips or with boosting, it has only pushed coolant at idle after 2hr+ plus drive when coolant has leaked out of the radiator, presumably from the water pump leak.

Will having air impregnated over pressurize the system and then displace coolant to the reservoir?