speedking

2006 Spec D <40000 miles

About a month ago I undertook a spirited drive from Carmarthen to Warrington.

Two weeks later while carrying out the regular fluids and pressures check, noticed that the coolant had gone down from full to the low line and there was an oily deposit in the coolant header tank. Not just a film on the water, but enough coating to pick out with a toothbrush. No warning lights, no increased coolant temperature on the gauge, no mayo on the oil filler cap, never had to top up before.

Now I know it is potentially a HG failure, and that some think this is common on these vehicles.

Since then I have done several hundred miles. Generally short journeys, shortshifting. But I have revved up a bit and done a couple of 30 mile trips. Nothing untoward.

So is it inevitably HG or could it be something else?

Are there any checks or tests that I could do to determine the cause?

Can I just carry on driving and see if there is a repeat, what am I risking?

Where has the coolant gone, is it a given that oil in the water means water in the oil?

How much is a HG replacement?

Are there any sensible mods to make at the same time if the headgaskets do have to be done?

One thought is to change the coolant and see if the contamination repeats under normal driving conditions. What is the easiest way to get the coolant out?

I have read this and this thread, but maybe there is more up to date info?

All advice gratefully received.

steviefastbikes

Gutted for you
I also have a spec d and worry about the same things
If you know anyone with access to emissions tester you could get them to put the sniffer above the coolant in header tank if it shows hc's then it is probably hg.

GeeDee

iTrader: (2)

From the OP of one of those linked threads don't waste your money on a Dealer checking the car over - £200 wasted with the report nothing wrong could be found!

I too immediately thought head gasket, but that was when it overheated suddenly one night at the end of a long journey. Same problem in the expansion tank though. ie oily scum and bits. but, confusingly, no loss of coolant other than when it oveflowed from the expansion tank.

I was in denial for a couple of months whilst I tried practically everything - I changed the coolant and nothing reappeared, I changed the thermostat (£15 and a few hours unlike the potential £200 at dealer prices!!) and I finally had a sniffer test which was not totally conclusive but gave a hint that it was head gasket.

The cooalnt can be drained from a drain point at the bottom of the radiator on the LHS looking from the front.

Good Luck

53

iTrader: (41)

Make your mind up time, keep and pre-emptive fix or sell

Not sure you can attribute it to a spirited run, unless you bought it new you have no idea of it's true service history and general upkeep.

Mine has done 2 trackdays no issues and I know of another standard spec D that's done a heap more to 95k miles and only now is the HG looking iffy. It's all down to upkeep IMHO and 95k is pretty respectable for HG that gets lots of abuse.

Personally my car never has issues, I like to think I mitigated/delayed any would be weaknesses in line with more reasonable wear and tear timescales by the regular upkeep and cooling measures I have taken.

I I were you I would stop now and get the HG done and engine refresh with new pistons. Or seriously trade it in and write the depreciation off in lieu of HG costs.

DantheMan2605

Hi,

I have the exact problem with my hawk sti. Sludge like coolant in resevoir. No loss of power, no overheating etc....

Ive been to subaru who are !$%%^ing useless, ive been to a specialist who have done the emissions test which came back negative. They have advised me that my rad hoses are breaking down. Give the hoses a squeeze, if they fold in on themselves (cold or warm) they are most likely on their way out as they should put up some sort of resistance. (An easy excuse for some silicone hoses)

Another thing i have been warned about is the oil cooler!
I had the AA out to charge the battery on my company van yesterday. And he got chatting to me about the scoob on the drive. Before he dropped it on my lap that he was a subaru technician for 16 years in america . Anywho he recommended i get the oil cooler checked, as if that has split and its leaking oil into the coolant it could be the cause for the hoses breaking down.

Ive noticed that when i pull over, within a minute my fans come on for the radiator and continue to run on and off for 30 seconds intervals.

Just a thought as there are other options before you go c**pping your pants about the head gasket. As i have been for a while. Anywho if the head gasket was gone i think youd know about it.

speedking

Pants clean. Monitoring the situation. Still driving. Thanks for the tips.

@53WRX the service history was poor, but the discount will offset any HG costs.

Does anyone know what the sniff test actually detects? If HCs then the amount of oil in the header tank would probably be enough and I don't need a test for that!

steviefastbikes

By products of combustion. Hc in gas form not liquid like sludge that would give off residuals only. Very low reading.
The hc's should creep up when the engine gets hot whereas residuals will be present from cold
Apologies for punctuation and spelling I am new to this way of comms

cster

When my HG went, there was actually bubbling coming through the top up/reservoir tank.
Plus the sludge etc.

wrx fifer

iTrader: (34)

so is the spec d more prone to hg failure than other models?

Butty

iTrader: (2)

My Spec d had the same thing at about 30k miles. It led to progressive failing of the HGs all at the same point of the cylinder bores.
There was a build-up of black particles that break up easily. this is the sealant layer from the HG faces.
By topping up the coolant and bleeding the system, I avoided overheating and really damaging the engine. I was able to go another 10K miles before I sorted it.
The coolant is being lost when you develop boost which forces coolant into the overflow bottle. This eventually overflows, but when the engine cools down the level drops - so you don't spot it.
The gas sniffer test didn't work as boost is required to see the problem - this cannot be done while not moving.

To replace the HGs should be IRO £750-£1000. remember to get the heads checked for warping. While the engine is out, it gives a good opportunity to fit some better pistons that allegedly have ringland problems.

dynamix

iTrader: (3)

The sludge is the thermostat breaking down. Fit a new thermostat and problem should be solved or better still an uprated thermostat like the zerosports one.

Same happened to mine when it was almost standard

speedking

A pre-emptive fix is only a pre-emptive fix if you are curing an actual problem. Otherwise it could be £1000+ and you still have the original problem

Keeping an eye on the thermostat now.

Have increased revs, boost, distance travelled with no bad signs so far.

greatgonzo

iTrader: (1)

How can you keep an eye on the thermostat?

53

iTrader: (41)

Not if you change the right bits

If you haven't fitted a zerosports thermostat I'd start with that tbh I fitted one pre-emptively runs lovely and cool

speedking

Strictly speaking, keeping an eye on the temperture gauge for unusual readings, and monitoring that the heating comes on as expected.

rob84

iTrader: (5)

the temp gauge isnt the best in an impreza unless your reading via a scan tool from the obd port. mine buggered a headgasket and was sitting well above 110c and the gauge read as normal.

53

iTrader: (41)

Scangauge is a good investment Pre thermostat change is used to read 88-93 hottest reading 95 at lights. Normal running temps, post Zerosports stat runs 78-84 hottest 91 at lights. This is driving hard on track and road

Myles

iTrader: (40)

Sorry for the thread hijack, but what benefits does running with a Zerosports thermostat, and does the STI 'stat that a couple have been selling on here give the same positives?

Thanks

Myles

speedking

My (traditional) understanding of a thermostat is that it is closed when cold and retains the coolant in the engine allowing the engine to warm up quicker. When the coolant reaches a certain temperature, the thermostat opens allowing the water to circulate through the heater, radiator etc.

Eventually the system reaches a steady state when the heat put into the coolant by the engine balances the heat removed by the heater, radiator etc. This steady state temperature willl vary with ambient temperature, engine output etc.

Generally as speed increases, so does the heat input, cooling effect, circulation, so temperature range doesn't vary much.

@53WRX. I guess that modern engines have more feedback loops and control systems, but I don't see how a different thermostat design would make the engine generally run cooler once it has reached steady state.

I see the advantage of failing open, but without additional cooling, can't see any other benefits. Perhaps the thermostat opens cooler and so on short journeys the temps will be lower. But after all of Subaru's R&D I doubt whether another temperature regime will improve on the factory standard one.

53

iTrader: (41)

Or build an engine with a high rate of HG failure ?

Can only tell you that on both my current scoobs, running temps dropped over the range by up to 10 degrees on both road and track and this is a common result.

speedking

Update: for over three months have been driving normally, after a slow start have built up to pre-issue levels of revs, boost etc. But as luck would have it, max. journey length approx. 100 miles. No issues observed at all.

This weekend we set off for Cornwall. 100 miles fine, then temp. gauge rose to max-ish. Stopped 20 miles later, let everything cool down. A small amount (100ml?) water had to be added. No other signs.

Set off again, temp. gauge needle rose to below shaded part at top of gauge and sat there, drove off boost. Arrived in Cornwall, no other signs of problems. Small amount of water added again. Drove home from Cornwall off boost, short shifting, with temp. gauge varying from 2/3 to max. Seemed unrelated to load, whether coasting downhill, external temperature, etc.

Is this symptomatic of a failed thermostat, or a failed HG?

dynamix

iTrader: (3)

thermostat imo

rich_g3

Hi Speedking,
This is exactly the same as what happened to me and in a nutshell IMO definitely HG Failure.
I've nearly finished running the engine in on the RB after rebuilding with Forged Pistons, Rings, ARP head studs, Cosworth Gaskets etc..
Tried all the other stuff Thermostat, faulty gauge, blocked radiator etc but wished I'd not wasted my time,
Hope you get it fixed soon mate

speedking

Replaced the thermostat last weekend; made no difference. So HG it is

Denmark

iTrader: (2)

To test for broken headgasket remove the hose that goes from the headertank to the overflow tank and replace it with a hose that goes from the headertank overflow and onto the windscreen,
Then go for a drive, give it some boost , if there is water all over your winscreen ,
Its eigther you header tankcap , or most likely ,
Your headgasket .....

Now go for a testdrive and stop speculating
Headgasket it is

/Skassa

speedking

Not in denial but ... is waterpump failure a possibility?

rob84

iTrader: (5)

not very common to be honest, they usually squeal like mad or you get noises from them when running if they fail.

i'd get those headgaskets sorted before it costs an even bigger bill