1998 WRX STi Overheating

[liamscooby]

Good evening!

I'm a new member to the forum and a new Impreza owner. Always fancied one and now I have one!

I have done a few searches on the forum but can't seem to find a relevant thread. Hopefully someone on here can give me some advice.

I recently purchased a 1998 Impreza WRX Sti. 2.0 turbo. Its a Japanese model. 

When run the engine begins to overheat after a while, even at idle. I opened the header tank to find a lot of rusty gunk inside. Ive cleaned the inside of the tank and also cleared out a couple of the hoses, it seems the previous owner has been topping up with water rather than coolant. Im going to take the radiator hoses off tomorrow and see if they are also gunked up. 

What is my best course of action to diagnose the overheating issue? My biggest fear is that it could be the head gasket, however I'm not seeing the telltale white gunk on the oil filler cap. My suspicion is that if the hoses are anything like the header tank then it could be that one of those is blocked. Other lines of investigation I'm thinking is the water pump or the thermostat. 

 

Anyone any clues or tips? Any assistance is much appreciated.

[Linx]

Hi and welcome to the forum [emoji106].
I'd run some radflush through it and change the thermostat to start with.

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[liamscooby]

23 minutes ago, Linx said:

Hi and welcome to the forum .
I'd run some radflush through it and change the thermostat to start with.

Sent from my HTC Desire 530 using Tapatalk
 

Brilliant, cheers for the reply, I'll give that a go. I should be able to change the thermostat without removing the water pump shouldn't I? I know to get the pump off removing the timing belt is required, would like to avoid that if possible. 

[savage bulldogs]

Hi n welcome. 

Yep ,waterpump is accessible from underneath 2x 10mm bolts on the housing and no need to undo the timing belt covers 😉

 

[liamscooby]

3 minutes ago, savage bulldogs said:

Hi n welcome. 

Yep ,waterpump is accessible from underneath 2x 10mm bolts on the housing and no need to undo the timing belt covers 😉

 

Now that is reassuring! In that case I might take the pump out and inspect it. Judging by the amount of sludge in the header I can't imagine its done the pump any good. 

[Linx]

He means thermostat not pump [emoji4]

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[liamscooby]

Just now, Linx said:

He means thermostat not pump

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Ah! Got ya, makes sense. At least I can rule that out before moving onwards.

[savage bulldogs]

Doh yeah thermostat , that's day drinking for ya .

Here's a pic of the front of the engine for reference 

And with the cover on , thermostat is accessible 

Waterpump is driven by the timing belt unfortunately 

[liamscooby]

2 hours ago, savage bulldogs said:

Doh yeah thermostat , that's day drinking for ya .

Here's a pic of the front of the engine for reference 

And with the cover on , thermostat is accessible 

Waterpump is driven by the timing belt unfortunately 

That’s great, really appreciate the photos and advice. Hopefully get chance to remove it tomorrow and test it. 

[liamscooby]

So this morning I took that radiator off, back flushed that and its running clear, so that's one less location for a blockage. 

 

This is where it gets interesting. I removed the thermostat... and half of it is missing... any ideas? My suspicion is that its been bodged to be blocked open all the time?  oh and the bubbles are just washing up liquid, gave it a clean so I could have a look.

I'm going to price up having the head gasket changed, head skimmed and water pump replace along with the timing belt. Anyone got any ideas on how much I should be paying?

 

Again, help much appreciated!

[Linx]

Is it possible that part on the thermostat has broken out and is still in the engine somewhere? Surely if you thought it was causing a problem you'd just take the whole thing out!??

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[liamscooby]

8 minutes ago, Linx said:

Is it possible that part on the thermostat has broken out and is still in the engine somewhere? Surely if you thought it was causing a problem you'd just take the whole thing out!??

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My thoughts exactly. unless you need half of it in for a seal? God knows.

Ive been on the phone and someone is selling an engine locally. The local mechanic said he could probs drop the new engine in for less that the cost of the head gasket and extra gubbins on this one. So that is an option at this stage. At least then I have a second engine for spares. 

[Linx]

Great. Do you know anything about the spare engine?

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[liamscooby]

45 minutes ago, Linx said:

Great. Do you know anything about the spare engine?

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Not as of yet, calling back tomorrow to get the details. He said it had been imported from the USA and was in good nick. Would be good peace of mind knowing the engine was all squared away so I could start working on the rest of the car. I’ll update once I’ve got more details. 

[stuartie]

I would also run the hose through the heater matrix aswell i done mine and loads of rusty s**t came out, you just need the take the 2 rubber pipes off where they come out the bulk head 👍

[savage bulldogs]

Just beware that you will only be able to fit a v1 92 to v4 98 long engine (engine and heads ) into a v4 sti , even then you'd need to swap a few bits ove from a v1/v2 long block to make it fit .

The v4 sti has the most aggressive cams and valvetrain fitted to classics and the heads sell for £500 + second hand. 

It does look like someone has taken the centre of the thermostat out , possibly to hide a overheating issue but for the cost of a new one .I'd not give up just yet .

 

As stu said trying flushing any inlet and outlet through with a hosepipe so ,heater matrix , pipes on the back of the engine (that heater matrix connects to) top hose ,turbo hose , header tank ect .

Then check the spark plugs for signs of burning coolant,  as scooby engines hardly ever mix oil and water .if the headgaskets do go ,they either pressurize the coolant with combustion gasses or burn coolant. 

So if everything flows freely and plugs are good , maybe try putting it back together with a new stat ,make sure you bleed the coolant system properly when refilling and see if it does it again while idling or driving off boost .

[liamscooby]

17 hours ago, savage bulldogs said:

Just beware that you will only be able to fit a v1 92 to v4 98 long engine (engine and heads ) into a v4 sti , even then you'd need to swap a few bits ove from a v1/v2 long block to make it fit .

The v4 sti has the most aggressive cams and valvetrain fitted to classics and the heads sell for £500 + second hand. 

It does look like someone has taken the centre of the thermostat out , possibly to hide a overheating issue but for the cost of a new one .I'd not give up just yet .

 

As stu said trying flushing any inlet and outlet through with a hosepipe so ,heater matrix , pipes on the back of the engine (that heater matrix connects to) top hose ,turbo hose , header tank ect .

Then check the spark plugs for signs of burning coolant,  as scooby engines hardly ever mix oil and water .if the headgaskets do go ,they either pressurize the coolant with combustion gasses or burn coolant. 

So if everything flows freely and plugs are good , maybe try putting it back together with a new stat ,make sure you bleed the coolant system properly when refilling and see if it does it again while idling or driving off boost .

Thanks for the extensive reply. I appreciate you taking the time to give me advice. I know the car has a bit of a history of overheating, the guy who sold me it was very honest. Im hopefully getting more info on the replacement engine today. 

I worked my way around all the cooling related hoses, a few were blocked. Took the radiator out and that ran clear when flushed. When the engine is running, now that I've unblocked the hose from the coolant filler to the header tank I get constant bubbling in the filler. Ive taken a video below. 

Judging by the advice received here I am almost certain the head gasket has gone. The water is cold when bubbling, and as you said it's more likely for exhaust gasses to be released through the coolant that water getting into the cylinder. 

The new engine has 30,000 miles on it and would give me the peace of mind required, all for the same price quoted for getting the head gasket and associated bits and bobs done. Plus ill have a spare engine for parts.

 

Jus

[Linx]

Wow I've never seen a blown head gasket cause bubbling like that. Did it stop? Looks more like the system purging to me, and expansion tank over full.

[liamscooby]

15 minutes ago, Linx said:

Wow I've never seen a blown head gasket cause bubbling like that. Did it stop? Looks more like the system purging to me, and expansion tank over full.

I haven’t run it for an extended period as the engine begins to overheat. I’ll run it for a bit longer tomorrow to see if it calms down. 
 

On a side note, there is a pipe that comes off the filler in the video and goes into the wing. Do you know what this is for? 

[Linx]

19 minutes ago, liamscooby said:

I haven’t run it for an extended period as the engine begins to overheat. I’ll run it for a bit longer tomorrow to see if it calms down. 
 

On a side note, there is a pipe that comes off the filler in the video and goes into the wing. Do you know what this is for? 

I think it's just an overflow.

[savage bulldogs]

Yep that's a new one on me too , I've seen them bubble a bit but not ever that much .

My guess is the coolant blockages stopped flow and caused the engine to overheat and pop the headgaskets. 

Just bear in mind that only a v1 to v4 long block will fit , the head inlet ports are different on anything newer .so your inlet and engine loom won't work without major modifications 😉

[Tidgy]

personaly i;d never buy a second hand engine, unless the person selling has done every single mile on the engine and you trust them completly, you have no idea what condition its actualy in. If your planning to keep the car then i'd look at getting the existing engine stripped and assessed and go from there.