watty88

Hi all

Please bare with me as I'm not 100% sure how the cooling system works on cars, done some research but still not sure.

Noticed my engine temperature on the dash was sky high when I got back tonight, to be honest I had been for enthusiastic drive but did a lap round the block to try cool off a bit before pulling up home. Not sure if that wasn't enough and it's normal for the engine temp to go really high after a hard drive?

2.5 forged engine running 440bhp, gt2071r turbo, japspeed IC.

Any advice appreciated cheers.

scoober101

When you say sky high, you mean it hit the top or very near the top of the temp gauge? Has it overheated before? Does the temperature fluctuate/bounce up and down the gauge or stay high?

It could be a number of things:

Bad air lock
Knackered water pump
Split Hose
Low coolant level
Thermostat stuck in the closed position
Blocked radiator
Rad cap / header tank cap not holding pressure

And last but not least...

Head Gasket failure

However, dont assume the worst with head gasket yet as it could be something else. I had a similar overheating/temp fluctuating issue and it turned out to be - I think - knackered water pump.

I say 'I think' because I replaced almost every part of the cooling system outside the engine block and it solved the problem. New rad hoses, new thermostat, new radiator and new water pump. I think the water pump was knackered and causing cavitation (creating bubbles/air pressure) and forcing the coolant out of the cooling system and dumping it into the expansion reservior (clear tank on side of radiator) or all over the road. Meaning the coolant level was getting lower and the system became badly air locked.

Thats my theory anyway.

Hope that helps.

watty88

Thanks for the reply, it didn't hit the top but was very close, seemed to fluctuate a bit/up and down but then stayed up high. There seemed to be coolant or some sort of liquid near the expansion reservoir (I think that's what it is) on the right hand side and splashed on the boost pipe going into the IC? I'd hope it wouldn't be the head gasket as part of the build it was upgraded to a cosworth one I think and only 10,000 miles ago.

Haven't noticed it overheating before, the map got tweaked after new injectors last week.

Might be worth running it through to Richard Henrys in the morning.

scoober101

Sounds like air is being introduced to the cooling system somewhere, what year/model scoob is it?

Using my car as an example - but I think all scoobies are the same setup - the expansion reservoir catches fluid that pushes past the radiator cap pressure seal. Thats its only source of fluid. So if that reservoir is full/overflowing then coolant is pushing past the rad cap and could be spraying out if its not all being caught in the reservoir, hence you have fluid on the charge air pipe.

Just need to find out whats causing the air to get in to the cooling system now.

FYI, Subarus are notorious for having a high chance of air locking if the cooling system is not refilled properly, I believe its thanks to a coolant crossover pipe that sits on top of the engine so if the system is refilled by the wrong method and too quickly, air locks will develop and you cannot bleed the system of air easily at all.

Best method for refilling from alcazar: https://www.scoobynet.com/general-te...l#post11465631

watty88

Yea that makes sense, there's is a bit of a gargling noise once I've turned engine off also like there's a bit of air trapped. It's a 2009 STI hatch.

Thanks a lot for the reply, you know your stuff ��

scoober101

Yep, had the same symptom myself, the gargling comes from somewhere around the header tank - black tank in front of turbo - and you will probably have bubbles also in the radiator expansion reservoir when the engine is hot/running. Pop the plastic yellow cap - NOT the rad cap! - and take a looksey.

Same car too, mine is a 2008 STI Hatch.

Has the water pump ever been changed? How many miles on the clock?

watty88

Yea that's where the gargling is coming from and yea that's exactly right I did see bubbles in the radiator reservoir whilst hot.

I'm not sure it has you know, the build got done about 10k ago but don't remember seeing paperwork for the water pump. Clock is on 61k now. Would imagine it will need changing now now, is it still safe for me to use the car or am I best off not driving?

What's spec on your hatch?

watty88

Sorry just looked through history and mods list and it got done with the build, gates cambelt kit + water pump

bustaMOVEs

iTrader: (31)

You've got combustion gases coming into your coolant, either way don't sound good.

scoober101

^ Not necessarily, I had the same issue as the OP and suspected HG myself, but after changing the cooling system components, problem solved.

Watty88 - it's got a full decat Magnaflow exhaust and been remapped but I don't know what to lol. I need to do a rolling road and see what power it's on as well as get the ecu map checked. Car had been remapped by one of the previous owners but the details of the remap - carried out by JGM, may he rest in peace - had been lost.

Vxr2010

run the car and check the non pressured expenasion tank for bubbles if it's bubbling a fair bit it's likely to be hg , when the non pressured tank fills up does the coolant return when car fully cools down ? if it does not that's not good , and when it's cold and you open the cap on the pressured tank is it low on coolant , if above the case then again most likely hg

boosted

Don't forget faulty rad fans

trevsjwood

iTrader: (2)

any uprated engine and in particular a 2.5 should run an aftermarket water temp gauge.
The standard gauge parameters are too wide before it starts to react to changes in temperature.
Trev

watty88

It's not bubbling much at all to be honest, the water is returning to the rad once cooled down also.

I took it down to Richard Henrys this morning, everything seemed fine didn't overheat at all, fan was working as it should as was everything else. Going to try a different thermostat. There was oil within the coolant system but didn't really show any other signs that it could be head gasket. No more white smoke/condescension that normal from exhaust when cold and nothing once upto temperature. Just hoping that the previous owner had a blonde moment and put oil where he shouldn't have or oil and crap in there still from before the build as wasn't overly long ago.

Hasn't overheated today after a bit of a hard drive either so hope it was a random one.

JDM_Stig

iTrader: (3)

Sniff test is best way to check for hydrocarbons in the coolant

trevsjwood

iTrader: (2)

the cooling system should work as regular as clockwork with no variations.
the coolant level in the expansion bottle shouldn't vary from the engine just being hot from driving around town, to getting full boost on a spirited drive on country roads/ track. I would be concerned about the coolant splashed around near the expansion bottle indicating pressures escaping from the engine into the cooling system.
Trev

scoober101

That doesn't sound good, should be zero oil and/or exhaust emissions in the cooling system. As JDM Stig said, a sniff test would indicate if its HG.

watty88

What do hydrocarbons smell like!? The lads at RH smelt the coolant but didn't say anything after. They also said it's strange because it's rare for oil to mix with coolant system with Subarus.

Out of interest how much is it roughly to replace HG?

JDM_Stig

iTrader: (3)

You dont snort it lol
The bubbles in the coolant give off a gas that changes the dye a different colour if present when using a sniff/leak/block tester(people use a few names for this test)

https://www.machinemart.co.uk/p/lase...Fewy0wod6y4P3Q

watty88

Hahaha well what was I supposed to think with a sniff test lol, right ok so would I use the sniff tester on the overfill res at the side of the rad? problem is today it wasn't bubbling at all.

JDM_Stig

iTrader: (3)

I use the header tank, but don`t rev the engine, just let it idle, or it will just force water into the kit, but you do have to hold it on nice and tight to seal.

watty88

Right ok thanks for the help mate. Is this when I've just started it up so it's not too hot I take it?

JDM_Stig

iTrader: (3)

full operating temp, but dont burn yourself.

watty88

Thanks ��

Vxr2010

sniff test did not work on mine ? i just knew it was going and got it done

scoober101

I don't understand what you mean. So the sniff test was negative but you still got the HG changed as you knew it was going...how do you know it's going if the sniff test was negative???

bustaMOVEs

iTrader: (31)

My sniff test came up ok too, problem is, you can't test it on boost and that's when it will happen. But if you have oil in cooolant, deffo hg failure of some sort.
Either heads are lifting on boost, warped heads, crack in block/heads.
My money's on hg/warped heads.

Vxr2010

the sniff test did not show it was going , the car was overheating but not all the time , and hg had gone which was causing the over heating

watty88

Either way whatever it is sounds like it's going to cost me a fair bit of brass :-/

Vxr2010

sorry but yes i think it will be hg , it sounds like classic hg issues , if you go rebuild route get arp head bolts or similar and cosi or the like gaskets as it helps that bit extra , your bottom end should be fine if it has been forged , the issue you have with yours even as a forged lump if it's putting out that power it's a lot more strain on every thing , if you want better reliability plus fuel economy i would get it down tuned , i recently did a 1 mile drag in a v8 , mines na the supercharged lot were only 20 mph more but were running a load more power mines 500 v some putting out nearly 700 , yes they are quicker but the higher tuned cars get more issues use more fuel so for me it's not worth it , i don't want a slow car either , i bet off the line a heavily tuned car v a standard car with a map yes heavily tuned probably quicker but not much in the time , i know it's been bought up many times , i prefer the 2.5 lump but they have there issues , but issues made worse or more likely with more power , a friend with a similar fsti tuned it all up turbos injectors etc , got problems and crap mpg , he now regrets what he did , it is at the end of the day your car your choice