Bazil_SW

iTrader: (4)

Hi all, this is my first post as I'm a new scooby owner. Just bought a totally stock 2006 Spec. D (I know, it must be a rare thing!) a few weeks ago from a dealer with a 12 months warranty. Firstly, what an amazing car! Very pleased with its performance, apart from.... I have an intermittent overheating problem that I'm hoping someone can advise on.

The conditions are:

- standard car, 2.5 turbo STI engine, apart from a K&N panel filter
- aircon on
- 40 mins or so of very 'spirited' driving on the country roads, engine temp is normal
- slow down for a roundabout in town, engine temp starts to climb
- 70 mph dual carriageway for 3 miles, engine temp starts to return to normal
- slow down for roundabout, engine temp starts to climb
- 70 mph dual carriageway for 2 miles, engine temp returns to normal
- slow down for town driving, engine temp starts to climb
- turn heaters on full and air con off to cool the engine, engine temp struggles to return to normal (and use the intercooler water spray, though not sure if I should?)
- max temp recorded ~115deg C (from a OBD data logger)

What I find strange is that the engine temp returns to normal on the dual carriageway, because of the increased airflow I guess, but then it starts to climb again once I slow down. After the first time this happened, the dealer changed the thermosat and replaced the coolant but it happened again afterwards (under the same conditions). Saturday morning I recreated it, but this time I checked the coolant expansion tank just as it was starting to overheat, it was bubbling vigorously and had a strong sweet smell, but I'm not really sure if there was a smell of exhaust gas or not.

Also when I start the car and rev it slightly there is gurgling and a water rushing sound from inside the dash, so I assume there is air in the coolant system, despite the dealers best efforts to bleed it fully.

There doesn't seem to any signs of leakage from the areas of the head gasket I can see without removing too much around the engine. I checked the spark plugs, they looked ok, gap, shape and colour wise. There doesn't seem to be any residue on the inside of the oil filler cap, nor does it seems to be consuming/loosing oil, but there might be a shimmer on the top of the coolant in the expansion tank, but not anything that looks obviously like oil.

Can anyone advise is this normal for the model, or (and I hope not) is this an early sign of headgasket failure?

The car has a warranty from the dealer I bought it from, but I want to build up the evidence if it's that, so they have no room wiggle out of replacing the gaskets...

Thanks in advance!

Tidgy

Have they done a snif test to check for headgasket failure?

Bazil_SW

iTrader: (4)

Not yet because they haven't actually been able to get it to overheat in the time they've had it for testing.

Just spoke to them, they want me to take a video of the temp gauge and bubbling in the expansion tank next time it occurs.

Tidgy

Sniff test is irrelevant of the overheating at that exact time, once the coolant is contaminated its contaminated and sniff test will show either way

**jay**

iTrader: (1)

Sounds like they are fobbing you off, take it too a specialist and get a sniff test done, or any garage really and get it diagnosed, symtems of 2.5 head gasket failer so id act now as warrenty company will try and get out of it

mistermexican

Bubbling in the expansion tank isn't necessarily a head gasket failure. Vapour from the turbo also causes this and is perfectly normal.

Overheating isn't though so best get it checked with a sniff test.

Bazil_SW

iTrader: (4)

Thanks for the replies, think I will book it in at my local garage and ask them to do the sniff test.

Today I did the same journey with no aircon as it was 13 deg c outside (instead of 20 as it was before) and no problem with overheating.

mistermexican

It could just be that it's being worked too hard for too long. 40 mins is quite a long time if using a lot of the rev range (in my opinion anyway). I've done two track days in mine and the coolant was bubbling once both times and I only do three laps at a time. Engine temp never went up though.

Bubbling behind the dash can also be normal. Mine does this sometimes on start up.

cuprajake

iTrader: (11)

The issue is boost, u can drive like a granny forever and have no issues, its the head lifting under boost and creating an air lock
Go out and give it the beans and fullboost, see what happens, sadly this happened to my standard spec d too

Tidgy

If it is the HG then its full rebuild time inc bottom end, highly likley to have damaged the crank bearings and they will fail very soon after if you just do the HG.

Mate found that out and it didnt even make it to being fully run in before it spat the crank.

Bazil_SW

iTrader: (4)

Admittedly I took it a little easier yesterday as we had heavy rain and the road was pretty greasy.

It's an interesting comment about the airlock, as the first time (of 3) that its happened the cabin heaters wouldn't get hot, it's what prompted the thermostat change. Can anyone explain the mechanism of the head lifting under pressure and creating an airlock, and other than driving with a less heavy right foot, what the fix is?

Tidgy

If HG has gone then return the car and get your money back. Proper rebuild will be 3k+ and they wont want to pay that so will either do a bodge job or a cheap second hand engine.

Plenty of em out there so not worth the risk

InTurbo

iTrader: (3)

My previous 06 sti had head gasket failure.. Bubbles in the expansion tank and constant water noise from behind the dash...
I could clear the air lock but it would come back.
Head gasket would leak exhaust gases into the coolant when driven hard so was a nightmare for the garage to diagnose. Had a few sniff tests and nothing,

I went and rented a hydrocarbon test kit myself then took the car out and gave it some boost,, pulled over and while the expansion bottle was bubbling i put the snif tester over it, turned green straight away.

InTurbo

iTrader: (3)

Basically the head bolts stretch under boost and exhaust gasses get past the head gasket into the cooling system.
This causes a air lock at the highest point the heater matrix, hence why you can hear water sloshing around.

The fix is to fit stronger head bolts and decent head gaskets, but as already posted your better off doing the bottom end bearings, if not a full rebuild for peace of mind.

Gambit

iTrader: (6)

headbolts dont stretch under boost they are not torqued correctly from factory which causes the headgasket problem on boost

my old spec D was running cosworth gaskets & std headbolts torqued to specific settings by tried & trusted engine builder over here and is still running grand from 2011 with 345bhp/395lbft

Bazil_SW

iTrader: (4)

That's a sizable and avoidable mistake on subaru's part if that's true.....

Think I need to get a sniff tester kit and do what InTurbo suggested, will video it to take to the dealers and see what they say, as a starter for 10.

Bazil_SW

iTrader: (4)

Hi all. Just a update on this. Firstly thanks for all the replies. It's looking likely that this issue will not be covered by the warranty, for one of 2 reasons (or both):

1) gasket failure is not covered by the warranty in any case, and
2) they would class the circumstances under which it occurs (full boost for extended periods) as ‘abusive’ driving, which is their #1 get out of jail free card

Both are a load of rubbish really, but accepting this, and not wanting to return the car, I started my own investigation. One thing I noticed is that there was a lot of debris on the radiator cap seal so I cleaned it off and made sure the seal was good again. Since then I’ve driven the car pretty hard a few times and noticed several things that are different:

- The bubbling in the expansion tank seems to have stopped or at least reduced significantly
- The rad hoses feel much harder when the engine is hot (so it seems there is more pressure in the system)
- There is less gurgling from the dash on start and engine rev
- The engine did start to overheat after the drive, but seemed to hold at a lower temperature that was only a bit higher than the normal “just below half way”. Previously it looked like it was going up to the dashed red lines before I turned off the engine.

However, these times round the ambient air temperature has been lower, between 13-15 instead of ~21deg C, and didn’t have the aircon on, so I guess there would be less heat soak from the aircon rad in this case, and the engine can cool better if the air flowing over the rad is cooler to start with.

I’m wondering if the debris on the rad cap seal was causing a poor seal / early release of coolant at a lower than rated pressure and causing it to boil as it was leaving. The factory fit rad cap is rated @ 137kPa (1.37 bar) release pressure. The service manual specifies the rad release pressure as 137+-14.7kPa (which is a max pressure of 1.51 bar), so I’m thinking of trying a slightly uprated cap to see if that can help.

I appreciate that if the head is leaking exhaust gas, this won’t fix the source of the problem but it might help to control it until I can get the proper fixes done: gaskets, headbolts, pistons, bearings etc. Current quotes are anywhere from £3-3.5k from various places around the midlands….

Tidgy

Has it been sniff tested?

mistermexican

If you get a new cap make sure it's the right one. The two caps in the engine are of different construction and rated at different pressure. The one on the rad is a relief cap only and the one near the turbo is a relief and vacuum cap.

Bazil_SW

iTrader: (4)

not sniff tested yet, waiting until payday to buy a kit for it.

yeah I clocked they were different when I was looking at the car and the service manual. It's the rad cap only I plan to replace at the moment.

mistermexican

People are probably going to have a go at me here but I still think that 40 mins is a very long time for the car to be driven under high boost. I think most of the bubbling will be coming from the cap near the turbo and it's probably emptied itself of coolant.
I may be wrong so I'd still get the sniff test.

Bazil_SW

iTrader: (4)

In a way you might be right. Taking it to the extreme, would anyone expect a standard car not to overheat or at least need special cool down from a decent hammering on a track? The difference perhaps is that the cabin heaters would still get hot, and that I'm not driving it as hard as someone would on a track!

Here when it happens the cabin heaters stop getting hot for a good while until I turn off, leave it for a bit and restart the engine. (At least that's what happened before I cleaned the rad cap)

mistermexican

When I went to track day I only did three to five laps at a time. Even the Ferrari only did 10 mins at a time and the GTRs did about 15. The rule of thumb is let it rest for at least the time that you were driving it hard.
I admit that yours is a bit of a funny one and I'm not an engineer but my friend is and works for GM in Detroit and even he said only do short bursts in them.
If you take the two caps the rad is 1.3 but the one near the turbo is 1.1 and on boost the turbo will get extremely hot and will vent. If it's like this for a prolonged period it could be pushing all the coolant vapour out and draining the heater matrix along with it causing the overhearing.
When you check the expansion how full is it when it bubbles?

Bazil_SW

iTrader: (4)

It's pretty full probably about an inch from the top when it was bubbling, but since I cleaned the cap it's not been so obvious.

mistermexican

Mine has done that once or twice but only on track day. You can hear it venting if it bubbles if you put your ear next to the caps. This will at least tell you which cap it's coming from.