Recommendations for head gasket repair in the South East
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Recommendations for head gasket repair in the South East
Hi all,
As above, does anyone have any recommendations for someone to repair the head gasket on my GD WRX (EJ205) preferably in the Kent / Sussex / Surrey area?
Thanks
As above, does anyone have any recommendations for someone to repair the head gasket on my GD WRX (EJ205) preferably in the Kent / Sussex / Surrey area?
Thanks
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From: Birmingham
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Depends on the symptoms Impressa.
My issue was coolant not returning into the header tank from the overflow tank by the radiator - a classic HG sign, but I solved that for mine by replacing the genuine STI 1.3 bar header tank cap with a genuine normal 1.1 bar cap - I think the return valve on the STI one had failed or at least become weak. This cap was 6 years old.
I also had I think a minor blockage in the return line from the overflow tank to the header tank - quite possibly the cause of everything. I took the hose out of the overflow tank, blew through it and I was met with a very minor resistance, possibly a small blockage somewhere, but seems clear now.
Lastly, the actual radiator cap - I took it off and compressed it, the spring loaded mechanism felt quite crunchy and pretty stiff. This cap was 12 years old, I cleaned it with hot water and it freed up enough fine, but for the price I replaced that too. A good clean was perhaps all it needed but...
I now have the same amount of coolant overflowing into the tank by the radiator as is being sucked back on cooldown vacuum overnight....about 1.5 inches.
I do still get flash vapour pockets degassing in the overflow at hot idle after a drive (5p sized bubbles), but that's normal, one or two every second, especially on a built 2.5 - again can be HG, but...when the cooling fans come in, the vapour bubbles inside the coolant system collapse / dissolve back into a liquid state and stop showing in the overflow tank - true HG would not do this. True HG would turn the overflow tank into a jacuzzi - been there had that. HG compression gases do not change behaviour with cooling fans etc, micro vapour pockets do.
I think most of the flash vapour is from the turbo coolant loop that cools the CHRA - turbo core. The vapour pockets are micro sized (0.3mm) bubbles that when they reach the overflow tank have joined together and become one bigger bubble as they effectively vent to atmosphere by Subaru design - bit like a fizzy drink bottle, you don't see any bubbles, only when you open it. Possibly heads lifting after boost? - not very likely with ARP clamp force. Plus, exhaust gas bubbles don't dissolve like micro vapour pockets do when the fans come in.
Soft top radiator hose overnight - HG would remain hard. No bubbles in the header tank or overflow on cold start up - HG would bubble immediately etc.
At first I was preparing for a HG bill of around Ł2k but after a ton of research and only 35k miles ago having a fully forged build with Cosworth HG's / ARP head studs, I thought I'd try the caps first....glad I did.
I did not have any overheating conditions throughout any of this by the way. I reckon there's tons of 2.5 STi's out there that bubble in the overflow tank on hot idle after a run, but people don't tend to look for it, they perhaps just look at the level once switched off or check when stone cold.
There's every chance that my old STi cap began sucking in air on cooldown, so not so much vacuum was created. I had heater gurgle for a few seconds when pulling away cold, but I also got rid of that.
I started the car with the heater on hot, but the fan off. Drove for 12 minutes the put the fan on about to speed 1. After about 10 seconds I heard the air bubble migrate out of the heater core...not heard it since.
The next morning, I noticed there was a slightly bigger suck back of coolant overnight to cater for the now dislodged air.
Sorry to rattle on folks, but there's some info there that is accurate to my findings, bubble / vapour behaviour versus HG bubble behaviour and so on.
My issue was coolant not returning into the header tank from the overflow tank by the radiator - a classic HG sign, but I solved that for mine by replacing the genuine STI 1.3 bar header tank cap with a genuine normal 1.1 bar cap - I think the return valve on the STI one had failed or at least become weak. This cap was 6 years old.
I also had I think a minor blockage in the return line from the overflow tank to the header tank - quite possibly the cause of everything. I took the hose out of the overflow tank, blew through it and I was met with a very minor resistance, possibly a small blockage somewhere, but seems clear now.
Lastly, the actual radiator cap - I took it off and compressed it, the spring loaded mechanism felt quite crunchy and pretty stiff. This cap was 12 years old, I cleaned it with hot water and it freed up enough fine, but for the price I replaced that too. A good clean was perhaps all it needed but...
I now have the same amount of coolant overflowing into the tank by the radiator as is being sucked back on cooldown vacuum overnight....about 1.5 inches.
I do still get flash vapour pockets degassing in the overflow at hot idle after a drive (5p sized bubbles), but that's normal, one or two every second, especially on a built 2.5 - again can be HG, but...when the cooling fans come in, the vapour bubbles inside the coolant system collapse / dissolve back into a liquid state and stop showing in the overflow tank - true HG would not do this. True HG would turn the overflow tank into a jacuzzi - been there had that. HG compression gases do not change behaviour with cooling fans etc, micro vapour pockets do.
I think most of the flash vapour is from the turbo coolant loop that cools the CHRA - turbo core. The vapour pockets are micro sized (0.3mm) bubbles that when they reach the overflow tank have joined together and become one bigger bubble as they effectively vent to atmosphere by Subaru design - bit like a fizzy drink bottle, you don't see any bubbles, only when you open it. Possibly heads lifting after boost? - not very likely with ARP clamp force. Plus, exhaust gas bubbles don't dissolve like micro vapour pockets do when the fans come in.
Soft top radiator hose overnight - HG would remain hard. No bubbles in the header tank or overflow on cold start up - HG would bubble immediately etc.
At first I was preparing for a HG bill of around Ł2k but after a ton of research and only 35k miles ago having a fully forged build with Cosworth HG's / ARP head studs, I thought I'd try the caps first....glad I did.
I did not have any overheating conditions throughout any of this by the way. I reckon there's tons of 2.5 STi's out there that bubble in the overflow tank on hot idle after a run, but people don't tend to look for it, they perhaps just look at the level once switched off or check when stone cold.
There's every chance that my old STi cap began sucking in air on cooldown, so not so much vacuum was created. I had heater gurgle for a few seconds when pulling away cold, but I also got rid of that.
I started the car with the heater on hot, but the fan off. Drove for 12 minutes the put the fan on about to speed 1. After about 10 seconds I heard the air bubble migrate out of the heater core...not heard it since.
The next morning, I noticed there was a slightly bigger suck back of coolant overnight to cater for the now dislodged air.
Sorry to rattle on folks, but there's some info there that is accurate to my findings, bubble / vapour behaviour versus HG bubble behaviour and so on.
Last edited by Hawkeye D; Dec 21, 2025 at 10:15 PM.
Thread Starter
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From: England
NOSSY 89 / Hawkeye D - thanks for your replies.
Both caps were replaced with OEM caps a month ago whilst my Subaru guy was trying to diagnose the problem so I don't think it is them. He mentioned that the expansion tank had bubbles in but these seemed to get better after he put some steel seal through it however my main symptom of over heating after a run remains the same.
It is interesting you say that a blockage may have been the cause of everything, I initially suspected that but the garage say they've flushed it through a few times.
"Soft top radiator hose overnight - HG would remain hard. No bubbles in the header tank or overflow on cold start up - HG would bubble immediately etc." - I'll have a look a this over xmas when I've got some time.
It still feels like the HG is the prime suspect but I'm happy to take any other alternative thoughts or recommendations on someone in the South East who could give me a conclusive diagnosis.
Thanks
Both caps were replaced with OEM caps a month ago whilst my Subaru guy was trying to diagnose the problem so I don't think it is them. He mentioned that the expansion tank had bubbles in but these seemed to get better after he put some steel seal through it however my main symptom of over heating after a run remains the same.
It is interesting you say that a blockage may have been the cause of everything, I initially suspected that but the garage say they've flushed it through a few times.
"Soft top radiator hose overnight - HG would remain hard. No bubbles in the header tank or overflow on cold start up - HG would bubble immediately etc." - I'll have a look a this over xmas when I've got some time.
It still feels like the HG is the prime suspect but I'm happy to take any other alternative thoughts or recommendations on someone in the South East who could give me a conclusive diagnosis.
Thanks
Slowboy racing in brands hatch.
https://www.slowboy-racing.co.uk/pro...nstall-rebuild
the link is for a rebuilt block etc, but I’m sure Neil/colleague can rebuild your block also/change hg etc.
he will give you no BS advice - best initially contacted on their WhatsApp number (at least in my experience)
https://www.slowboy-racing.co.uk/pro...nstall-rebuild
the link is for a rebuilt block etc, but I’m sure Neil/colleague can rebuild your block also/change hg etc.
he will give you no BS advice - best initially contacted on their WhatsApp number (at least in my experience)
Scooby Regular
Joined: Mar 2021
Posts: 1,324
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From: UK
Last i asked Slowboy about engine job they sent me to Rcm.
Best advises i had from Fbtuning and Andy Williams.
Went with Andy as Fbtuning was to busy.
Asperformance is very good to but he prefer to have engine removed from a car for him.
Best advises i had from Fbtuning and Andy Williams.
Went with Andy as Fbtuning was to busy.
Asperformance is very good to but he prefer to have engine removed from a car for him.
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Thread Starter
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Joined: Jun 2023
Posts: 11
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From: England
Thanks for the advice on this. Thought I'd update with the resolution.
Took it to Slowboy Racing near Brands Hatch and they diagnosed HG failure. I briefly considered a short block replacement but in the end couldn't justify the cost (Ł7.3K) so went for the HG repair for Ł3.4K.
Very professional job from Neil at Slowboy, took about a week and now the car drives like new.
Took it to Slowboy Racing near Brands Hatch and they diagnosed HG failure. I briefly considered a short block replacement but in the end couldn't justify the cost (Ł7.3K) so went for the HG repair for Ł3.4K.
Very professional job from Neil at Slowboy, took about a week and now the car drives like new.
Depends on the symptoms Impressa.
My issue was coolant not returning into the header tank from the overflow tank by the radiator - a classic HG sign, but I solved that for mine by replacing the genuine STI 1.3 bar header tank cap with a genuine normal 1.1 bar cap - I think the return valve on the STI one had failed or at least become weak. This cap was 6 years old.
I also had I think a minor blockage in the return line from the overflow tank to the header tank - quite possibly the cause of everything. I took the hose out of the overflow tank, blew through it and I was met with a very minor resistance, possibly a small blockage somewhere, but seems clear now.
Lastly, the actual radiator cap - I took it off and compressed it, the spring loaded mechanism felt quite crunchy and pretty stiff. This cap was 12 years old, I cleaned it with hot water and it freed up enough fine, but for the price I replaced that too. A good clean was perhaps all it needed but...
I now have the same amount of coolant overflowing into the tank by the radiator as is being sucked back on cooldown vacuum overnight....about 1.5 inches.
I do still get flash vapour pockets degassing in the overflow at hot idle after a drive (5p sized bubbles), but that's normal, one or two every second, especially on a built 2.5 - again can be HG, but...when the cooling fans come in, the vapour bubbles inside the coolant system collapse / dissolve back into a liquid state and stop showing in the overflow tank - true HG would not do this. True HG would turn the overflow tank into a jacuzzi - been there had that. HG compression gases do not change behaviour with cooling fans etc, micro vapour pockets do.
I think most of the flash vapour is from the turbo coolant loop that cools the CHRA - turbo core. The vapour pockets are micro sized (0.3mm) bubbles that when they reach the overflow tank have joined together and become one bigger bubble as they effectively vent to atmosphere by Subaru design - bit like a fizzy drink bottle, you don't see any bubbles, only when you open it. Possibly heads lifting after boost? - not very likely with ARP clamp force. Plus, exhaust gas bubbles don't dissolve like micro vapour pockets do when the fans come in.
Soft top radiator hose overnight - HG would remain hard. No bubbles in the header tank or overflow on cold start up - HG would bubble immediately etc.
At first I was preparing for a HG bill of around Ł2k but after a ton of research and only 35k miles ago having a fully forged build with Cosworth HG's / ARP head studs, I thought I'd try the caps first....glad I did.
I did not have any overheating conditions throughout any of this by the way. I reckon there's tons of 2.5 STi's out there that bubble in the overflow tank on hot idle after a run, but people don't tend to look for it, they perhaps just look at the level once switched off or check when stone cold.
There's every chance that my old STi cap began sucking in air on cooldown, so not so much vacuum was created. I had heater gurgle for a few seconds when pulling away cold, but I also got rid of that.
I started the car with the heater on hot, but the fan off. Drove for 12 minutes the put the fan on about to speed 1. After about 10 seconds I heard the air bubble migrate out of the heater core...not heard it since.
The next morning, I noticed there was a slightly bigger suck back of coolant overnight to cater for the now dislodged air.
Sorry to rattle on folks, but there's some info there that is accurate to my findings, bubble / vapour behaviour versus HG bubble behaviour and so on.
My issue was coolant not returning into the header tank from the overflow tank by the radiator - a classic HG sign, but I solved that for mine by replacing the genuine STI 1.3 bar header tank cap with a genuine normal 1.1 bar cap - I think the return valve on the STI one had failed or at least become weak. This cap was 6 years old.
I also had I think a minor blockage in the return line from the overflow tank to the header tank - quite possibly the cause of everything. I took the hose out of the overflow tank, blew through it and I was met with a very minor resistance, possibly a small blockage somewhere, but seems clear now.
Lastly, the actual radiator cap - I took it off and compressed it, the spring loaded mechanism felt quite crunchy and pretty stiff. This cap was 12 years old, I cleaned it with hot water and it freed up enough fine, but for the price I replaced that too. A good clean was perhaps all it needed but...
I now have the same amount of coolant overflowing into the tank by the radiator as is being sucked back on cooldown vacuum overnight....about 1.5 inches.
I do still get flash vapour pockets degassing in the overflow at hot idle after a drive (5p sized bubbles), but that's normal, one or two every second, especially on a built 2.5 - again can be HG, but...when the cooling fans come in, the vapour bubbles inside the coolant system collapse / dissolve back into a liquid state and stop showing in the overflow tank - true HG would not do this. True HG would turn the overflow tank into a jacuzzi - been there had that. HG compression gases do not change behaviour with cooling fans etc, micro vapour pockets do.
I think most of the flash vapour is from the turbo coolant loop that cools the CHRA - turbo core. The vapour pockets are micro sized (0.3mm) bubbles that when they reach the overflow tank have joined together and become one bigger bubble as they effectively vent to atmosphere by Subaru design - bit like a fizzy drink bottle, you don't see any bubbles, only when you open it. Possibly heads lifting after boost? - not very likely with ARP clamp force. Plus, exhaust gas bubbles don't dissolve like micro vapour pockets do when the fans come in.
Soft top radiator hose overnight - HG would remain hard. No bubbles in the header tank or overflow on cold start up - HG would bubble immediately etc.
At first I was preparing for a HG bill of around Ł2k but after a ton of research and only 35k miles ago having a fully forged build with Cosworth HG's / ARP head studs, I thought I'd try the caps first....glad I did.
I did not have any overheating conditions throughout any of this by the way. I reckon there's tons of 2.5 STi's out there that bubble in the overflow tank on hot idle after a run, but people don't tend to look for it, they perhaps just look at the level once switched off or check when stone cold.
There's every chance that my old STi cap began sucking in air on cooldown, so not so much vacuum was created. I had heater gurgle for a few seconds when pulling away cold, but I also got rid of that.
I started the car with the heater on hot, but the fan off. Drove for 12 minutes the put the fan on about to speed 1. After about 10 seconds I heard the air bubble migrate out of the heater core...not heard it since.
The next morning, I noticed there was a slightly bigger suck back of coolant overnight to cater for the now dislodged air.
Sorry to rattle on folks, but there's some info there that is accurate to my findings, bubble / vapour behaviour versus HG bubble behaviour and so on.
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Joined: Oct 2011
Posts: 3,061
Likes: 479
From: Birmingham
Thanks for the advice on this. Thought I'd update with the resolution.
Took it to Slowboy Racing near Brands Hatch and they diagnosed HG failure. I briefly considered a short block replacement but in the end couldn't justify the cost (Ł7.3K) so went for the HG repair for Ł3.4K.
Very professional job from Neil at Slowboy, took about a week and now the car drives like new.
Took it to Slowboy Racing near Brands Hatch and they diagnosed HG failure. I briefly considered a short block replacement but in the end couldn't justify the cost (Ł7.3K) so went for the HG repair for Ł3.4K.
Very professional job from Neil at Slowboy, took about a week and now the car drives like new.
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