Cant believe the first thread I start is about a potential head gasket problem.

I just got the car for a week, on the next day I got it I checked the oil and the coolant level by removing the radiator cap.

Everything runs fine until few days ago I boost it, the overflow tank has been filled up and it spilled some water to the engine.I can see smoke coming out from the engine due to burning off the spilled coolant.

So I parked up, let it cool down a bit and open up the cap on the reservoir bottle, added some water in it. I squeezed the top radiator hose and it has air bubble coming out from the reservoir tank. I guess it’s when I open the radiator cap, air goes into the system?

I manage to drive back home under boost. Then this morning I checked the overflow tank and it is empty. I think it sucks the coolant back in once it’s cooled down.

I opened the reservoir cap, started the engine, try to squeeze more air out from the radiator hose, and top it up. I did a test drive on boost and the overflow tank still filling up. So I let it cool down again, open the reservoir cap and repeat the process. I can see little bubbles coming out. When I floor it to 2000rpm and let go, the level in reservoir goes down and come out with more bubbles.

The Oil Pressure, Oil Temp and Water Temp are all normal. Coolant and oil does look normal and no funny smell from the exhaust. It does not over heat or lose boost. I also have Cosworth 1.5 bar radiator cap and a normal cap on the reservoir bottle.
I know this might be HG failure, but before I replace it, any other things I can check?
In worse case if it is HG, how much will I be looking to get it replaced?

Will greatly appreciate for all your advice.

 

I would start with a complete coolant change using the proper method on here. You can't bleed the impreza cooling system so start fresh and see what happens from there. Also not 100 percent on this but think the upgraded radiator cap you have would be increasing the boiling point? Somebody will correct me on that one.

 

Put some water in the overflow bottle next to the rad, rev the engine if bubbles appear then the head gasket is fooked.

This will mean it needs FULL engine rebuild or a replacement engine.

 

is there no other way to completely bleed the system? I have searched on this problem, but seems.other have overheat as well which i don't have.

Is it that easy to check if its blown head gasket? If i have air in the system, shouldnt it be pushing out from the overflow tank as well?

In general, do you guys have any water in the overflow tank? I read something like ppl fill it up to half full.

 

If you do what I said then you'll have the answer to all your questions. Then if there's no bubbles drain the system and refill through the water hose that goes to the turbo using a funnel, very slow process but the only way to make sure you don't get air locks.

 

Or just get a sniff test done??

 

Some head gaskets don't show unless under boost. Do what ditch said first if no bubbles do a full change. You can't bleed it.

 

First thing you shoud do is bin the 1.5 bar rad cap. Its too high a pressure rating. It will make the system do funny things.

 

op you bought private or off a forecourt ?

 

i bought it private. i believe it was using 1.3 bar before but it have some leaks and changed to 1.5.

quick question, is it true i cant open the radiator cap?

 

Its fine when cold.

 

Thank you for all the advise.

This afternoon, I had a look on both radiator cap, it looks fine to me with no vistual damage.

I have did what ditchmyster stated, asked my gf to rev the car and I constantly looking at the overflow bottle, there is no bubble coming out, so I guess its a good sign?

I have also smell the exhaust and it smell normal.

I am cooling the car down at the moment and Im gonna check the overflow tank and resovoir tank again once its cooled down.

I guess once the car is cooled down, I can top up the resovoir tank if needed and test drive the car? or should I do a complete coolant change first?

Thank you again for all the advice.

 

You need to do a complete coolant change.

There is NO way to bleed the system and nothing will change by just topping up, sounds like someone bodged a coolant change on it and got air locks.

 

Thanks ditchmyster, looks like its a good sign.

Without any knowledge of this car, I guess best way to get a subaru specialist to change the coolant ? Or its quite easy to DIY? I do work on my car before but not to any Subaru.

Jst courious, what is the point of a complete coolant change rather than topping it up?

 

Like I said above you won't get the air locks out, I don't know the exact reason why, but I do know there is no way to bleed the system and remove the air locks, I think it's to do with the heater matrix and the design of the system. It needs to be filled from the highest point to purge all the air from the system.

 

Couple off foibles i have noticed in my limited ownership.
Firstly when you crack the red cap you allow air to enter the overflow pipe that leads to the expansion tank, when you replace the cap you effectively trap this air in the pipe.

When the coolant heats, it expands and pressure builds, once this pressure exceeds the caps rating it goes into the expansion tank via the expansion pipe.

This expanded coolant will flow along the expansion pipe pushing the trapped air in front, and when it enters the bottom of the ex tank it will bubble up the tank.

The coolant level rises and falls with the revs of the engine

A lot of talk about how its impossible to bleed the system, but from my experience of doing the job i had no problem.
I have a mechanic friend of the family who worked for a dealership for 40 years, 25 of those years they were a subaru dealership, i will ask him what the exact method subaru used to fill the coolant system was and report back.

A lot of mis information on this subject i think.

Cheers

 

Thanks for your input Martin.

I have tried to drive it on boost this afternoon.

First I check and make sure the level in the header tank is right. Close it up, warm up the car and drive it on boost. When I back and parked up, the overflow tank is full again with bubbles coming up.

So I am thinking:
1) Head gasket is gone but still in the beginning state, which only affect in boost.
2) There are air in the cooling system and they are being push out when the coolant expand
3) Radiator cap failure or there is a small leak which allows air to goes in?

I'm gonna buy both the head tank cap and radiator cap and try it again. If no success, I will completely bleed the system.

 

I had exactly the same problem and scratched my head for days as I couldn't see anything leaking at the time, then I noticed when I pulled into the drive one day steam coming out, I lifted the bonnet and noticed that only under Certain Temperature and presure there was a pin sized hole in my top radiator pipe where it jubilees near the block, that had been leaking slowly over time and ran my coolant level low, then when I topped the level up it bubbled in the overflow pipe for a little while until it settled down, check all your pipes first mate.

 

Thank you. But does it also cause the overflow bottle to filled up?

 

just got a quick look on the oil and water, both look normal. The overflow tank is empty now as seems it sucks back in to the system.

 

Not saying it is headgasket or not, but if it is the oil and water will not necessarily mix as per the layout of the engine.

 

quick questions guys, should the cap on the reservoir bottle and radiator be the same pressure? I want to change both of them to see how it goes.

 

As suggested before get a sniff test done. At least then you will know for sure if its HG or not. The kits are relatively cheap.

 

ya i called a local garage to do it later today. fingercross it will be ok!!

 

Any good?

 

Bad news!!!!!

Did the Sniff test and it changed colour.

I guess its nothing I can do except changing the head gasket.

I have did some research on the price but its all different. I have no idea what needs to be replace within the engine block.

I have got a aftermarket radiator system and clutch which installed not long ago so I should able to use my old one.

Do you guys have an idea roughly how much would it be for just changing the head gasket?

Also, if I am looking to upgrade the internal with stronger parts, what parts should I upgrade?

Many things again~

 

I would suggest getting a fully forged rebuild done at the same time the HGs are done. It would be unwise to not refresh the pistons, crank, bearings etc while the engine is out.

Not sure on the cost to just change the HGs, but as I said if you change the HGs then shortly after the internals give up, it'll end up costing you twice as much.

Give APi a call they'll be able to give you your best options based on your budget.

 

Any idea how much I will be looking for to get it fully forge?

I was thinking of that as well to give myself a piece of mind, at least I don't need to worry about it anymore, or it will be capable for more power if I want to in the future.

But of course, it will depends on how much it is.

 

I would estimate approx. £2500+ for a fully forged build. That's a total guess tho. All depends what spec you go for I guess. Best off ringing about for some prices, but people like API, Extreme Scoobies, Slowboy Racing etc all come vey highly recommended.

For the little extra its defiantly worth forging, not only will you have peace of mind but also the ability to up the power without worry.

 

CutMasterT, you never sleep at night like me?

I totally agree with you, but the trouble is I dont know anything inside the engine and what parts is use for or even what is it? Among my car history, I never play with an engine before.

When I call them, they will tell me a brunch of things which I have no clue on about.

Ideally I can ask them to send me a list of what needed and I can obtain the parts myself since I can get that in trade price.