Lots of air in coolant under boost!
 

I haven't had a lot of luck with my scoob! Here's my original thread;

https://www.scoobynet.com/general-te...r-upgrade.html

I've finally got around to getting the car built back up. I've fitted a sti8 topmount, second hand vf35, and built the engine back up using cometic head gaskets and all genuine bits. I was really careful building the engine back up and have built lots of engines before and never had any problems whatsoever...

I've moted it taxed it, insured it and even paid the subscription for the tracker, and had it booked in with jgm for a remap next tuesday.

I've taken the car for a bit of a run and found that it's pushing loads air into the coolant under boost. It's looking like it might be a head gasket, although the old ones were fine, heads flat etc... The only other thing I think it could be is the second hand turbo is somehow pushing air into the coolant?

I'm wondering whether to bypass the turbo with the coolant pipe and giving it a little bit of boost to see it it's still doing it, which would point at the head gaskets.

Has anyone ever come across a turbo pumping air into the coolant? or could there be something I've missed?

Cheers, Nathan

They can be tricky to bleed properly. Theres a step by step thread here somewhere.

It's not possible for a turbo to introduce air into the coolant, period. The coolant runs through a channel cast into the cartridge and is separated entirely from either the inlet air and exhaust tracts.

If (almost unheard of rare, but let's do the theory) the cartridge happened to crack, due to the cooling system being pressurised you'd get coolant leaking out of the turbo rather than air leaking into it. Maybe not what you want to hear, but at least it allows you to streamline your diagnostic process.

When the engine was rebuilt were the decks and heads cleaned of all crud and previous gasket residue? Was the tightening sequence performed to the letter of Cometic/Subaru's procedures?

Yeah, done all that loads of times. It'll be fine for as long as you keep it off boost, but as soon as you let it have any boost it pushes out so much air that coolant gets pushed out of the expansion tank!

did you have the heads pressure tested when they were off mate?

Yeah, That's what I thought about the turbo cartridge, just kind of hoed it wasn't an engine out job again!

Was really meticulous with the engine. Has it on my stand in a perfectly clean environment etc. Torqued everything up correctly in the correct sequence! Checked the heads and block, but only with a straight edge.

What I cant understand is that there were no problems with the engine at all before I took the heads off, I suppost the other thing would be a cracked head or something, but they were fine before!

looks like It has to be a head gasket, but I don't know how just doing it all again will fix it! Obviously its a multi layer metal gasket, but I haven't heard of problems with them before...

No, didn't have the heads pressure tested, but like I said, there were no problems with them before removing them.

I followed the sequence for removal, and checked them for flatness (admittedly only with a straight edge) and they seemed fine, unless just removing them could have allowed one to warp slightly?

not common but can happen in my garrage its rotine to skim just to cover your ass and to be fair astriaght edge wouldnt show aslight warp mate,abit rodermentry aint it fella on a 2.0 running quite serious power and boost?if it was apunto or something then ok but not something like this.

Yeah I know what you're saying, but as they wern't removed because of gasket problems, and not wanting to unnecessarily raise the compression, I decided (maybe stupidly!) not to skim them. I know from experience that certain heads can warp from just removing them, but normally I've been able to tell with a good straight edge and a fag paper. It's just that it seems like it must be really bad, as just the tinyest bit of boost and absolutely loads of air is pushed through!

quite alot of volume of air being produced by theses motors mind not just pressure so it wouldnt take much of a warp to get blow by.

Yaeh, a bit af a cock up the ass isn't it :brickwall Think I might be stripping it all again by the look of things. Suppost a sniffer test might confirm it, but it's looking pretty obvious isn't it!
I was hoping to get loads of replys saying that it's a common thing to get a turbo pressurising the coolant!

fraid not fella,and if shes fine off boost then id suspect that asniff test wont show anything,tough learning curve mate but we live and learn:thumb: heads up mate youll get there in the end and good job your not paying some 1 to do the work

If it's blown ANY exhaust gases into the the coolant a sniff test will show that in the header tank.
Sound desperately like either head gaskets or a cracked liner.

like he said though mate it doesnt get presurized on idle or off boost so the gases arent entering then so wouldnt show

The exhaust gas doesn't suddenly vanish the second you come off boost..
It WILL show

ask the man posting the problem then fella thats what he said so i cant comment more really but unless you were under the bonnet under accelration lol then IT WOULDNT SHOW cause if there isnt gas coming out of the header tank on idle or off boost then you cant get any reading simple really,but just going off what the man says

Then you need to go do the test or at least know what you are talking about!

I'm not arguing the toss with you any more. I do the test regularly.
Believe what you want

jesus whats wrong with some folk im just passing comment and giving advise on what some 1 is saying and i do the test regular myself mate i run agarage!but i can tell you if there isnt gas passing through the expansion tank then theres nothing to read off but you believe what you want also pal im done with this thread!

LOL, both of us in a paddy about it.

Lets just say the head gaskets are ****ed and leave it at that then

sounds good to me fella us scooby owners are to hot headed ah lol:thumb:

mine did that new set of HG from lateral and 6 hours later stoped doing it £150 all in as i did them my self.

Right, head gaskets it is then!

i had same thing mate when my engine was rebuilt i used the old head gaskets cos they were cosworths had same trouble as u went and got new ones and it was fine ...

Can exhaust gases get into the coolant ???? If possible would feel anything wrong with the car other than discolouration of the coolant? does this happen through the head gaskets :wonder:

If you run a garage I hope for the sake of your customers and your reputation that you give them a little more thought than you have this thread. Fuzz was entirely correct, and more than justified in engaging you on the point, given that this is a discussion forum and all.

If the head gasket is leaking under boost then the coolant will become contaminated with dissolved combustion components, and will stay contaminated even after you back off. Hence your claim that "if shes fine off boost then id suspect that asniff test wont show anything" was wrong. Once it's in there, it stays in there and a test will pick it up.

Appreciate you mean well but that's not the first bit of dodgy "comment" you've passed.

The coolant often isn't obviously discoloured, as above needs to be confirmed by a CO test. Whether you'd be able to feel anything wrong with the car depends largely on how serious the problem is. You wouldn't normally feel it in your right foot unless the leak was either very serious, or had been left long enough to drain all the coolant and cook the engine. Usually you'd spot it indirectly - either via your heater suddenly blowing cold, constant air bubbling into the coolant expansion tank air separator, or whatever.

And yes, it happens through a compromise in the head gasket between one or more of the combustion chambers and the coolant passages. Similarly if you get a failure between the coolant and the oil supplies/returns, you get oil in the coolant (or vice versa).

jabbawockymark they were new gaskets. I'm probably going to have to get the engine out and get everything tested & skimmed and another set of gaskets by the seem of things...

havent aclue what mr SPLITPIN is on about obviously feels that spouting aload of crap makes him feel knowligable but the fact still remains that for the sniff test to turn it has to have co pass through it and if none is coming through it,IT WONT,dissolved co in the coolant what are you on mate,some sort of a professor at uni are we shut up,and as for giving my customers the thought needed I DO because my diagnousis of faults and always on head gaskets has NEVER been wrong yet:hjtwofing comment on the co in the water is right but residule co doesnt always change the sniffer so as i stated it PROBABLY wont show anything is true,i know you mean well to mate but this thread had died and been figured out he didnt skim and payed the price end of,why some tossers have to try and get the last word in and try to make some 1 feel small is beyond me,and how can any off us be 100% right without going and diagnousing it any way.

Oh dear.

Question old boy: How do you think CO products find their way into the expansion tank when a head gasket fails? Are they put there by magic? Osmosis? Evaporation?

i dont know were your trying to take this fella but i know were the co comes from but the fact remains that the tiny amount left after he'd taken the cap of would PROBABLY not change the fluid colour[not defo] as he said its not pressurizing on idle or off boost so grow up and go give some 1 else all your amazing knowledge now bye bye:thumb:

Hahahaha, you still wont listen.
Seen plenty of Splitpins posts and every one of them are spot on and full explanations are given. A credit to the forum.
You need to wind your neck in a bit and realise we are both correct.