Brian Powell

Hi all,

Well where to start... First my header tank cracked... Brought a mishimoto header (aluminium one) and fitted and refilled.
Everything went good for 2 weeks, then my top hose pipe went. Luckily I was 2 meters away from parking at work.

As in true fashion, if you take something out, you put something bigger and better back in 🤫
I replaced the radiator with the mishimoto radiator and brought the hose kit aswell. Had to trim the hoses due to the bigger radiator etc.
*Mishimoto cap on header, original radiator cap on the mishimoto radiator*

When I refilled with coolant, while testing at home the bottom hose got warm (thermostat open), but since then the bottom hose doesn't get hot, despite having engine temps of 95..96..97 etc. The fans will turn on, and kinda keeps it at that temperature.
Reading up the fans should turn on at 95 for 30 seconds and drop the temperature down to 89. But this isn't happening.

I'm starting to think dodgy thermostat but before I grab a bigger hammer I wanted to check what you guys thought.

The car is a Subaru Impreza WRX Newage 2005, mods consist of remap (engine tuner 285 bhp), RCM headers, RCM uppipe, decat center, afterburner vortex and cosworth panel air filter.

Since problems started happening, only the mishimoto header tank, radiator and hoses have been put on.

Thanks for any advice 🙂

JDM_Stig

iTrader: (3)

Sounds like it could be head gasket, it is just finding the weakest link each time you up rate and replace imo,
Get a sniff test done before you keep changing parts.

hth

yabbadoo4

iTrader: (8)

good chance you have airlocked the system bud. drop the coolant and refill using the bottom fill method. pull off the rear hose on the header tank that feeds water to the turbo and stuff a funnel in there and fill slowly without any glugging and get a slow steady flow going. keep filling until you see the level come up in the header tank to the usual level and put the turbo water feed hose back on. start the car but leave the header tank cap off and let car tick over whilst burping the top radiator hose a few times to expel any leftover air. put the cap on and take her for a drive and see how you go. this method fills the radiator from the bottom as there is no way to bleed the coolant on a subaru. ive had a fair bit of grief with my sti and coolant issues and this method def seems to be the best way to avoid airlocking the system.

pjarvis6666

iTrader: (1)

is it the 2.5 engine?

Brian Powell

Yeah I was considering this, will get one booked in the next couple of days to remove this from the list. Cheers for the reply.

Hmm, this was another thought. Later tonight i'll be moving the car to a hill, and seeing if i can burp it. Otherwise its a full empty and fill again using your method. Thanks for the advice.

Nope it's a 2.0 EJ20 engine.

Thanks all for the advice

siluro

If it was an airlock It would probably overheat, the fans would not be able to control the temps. When the fans kick in to should cool to about 87-86 and then back up to 97. This cycle just repeats. I hope it is an airlock, or thermostat else I would suspect the HG. A sniff test may not be helpful but is worth trying. I have seen many stories of the sniff test coming out ok but eventually they changed the HGs and there was signs of the HG leaking into the coolant.

Good luck

siluro

This is good advise and how I did mine. I still get a bubbling sound from the heater matrix sometimes. When doing it park so the header tank is the highest part of the car, nose up on a slant may help. I filled mine with water for flush like this and still got an airlock. Pour slowly. Good luck again.

Brian Powell

Thanks for the advice, I've finally got a day off, so I'm gonna do this today. Hopefully the rain stays away!

Brian Powell

Yeah after doing abit more research it does seem this is the way to refill cooling system. I'm gonna go start now, I'll let you guys know how it goes.
Cheers for the help all

Brian Powell

Just abit more information for anyone else who's reading having the same issues, or who are just curious.

Problem started after fitting a mishimoto radiator, refilled... Seems I got a airlock somewhere in the system.
Symptoms were a car fighting itself trying to cool itself.
I am having temperatures of 96/97, fans turning on but keeping it at 96. Racing car (for 3 secs) does cool the car (3/4 degrees) due to additional cold air being forced through radiator etc.
Heater is hot inside car, but a very slight hint of anti freeze (loads poured into heatwrapped headers). From reading, heater matrix has water from radiator, and if it's starved of water it will drag air from the engine bay, explaining the smell of antifreeze)

Right time to get this car sorted!

siluro

Agh Mishimoto radiator could be your problem. I have seen other reports of faulty Mi****moto rads. Check all the small bore pipe connectors are not blocked. I remember one instance that this was blocked from new with bad welds. He had the same issues as you. Don't buy Mi****moto stuff it is junk.

Brian Powell

​​​​​​Yeah I saw the early versions of the mishimoto radiators had problems, but reading recent reviews they have sorted out the issues etc. I did look at all the pipes are welds and it's all good.

Well, ive drained and refilled via the header tank turbo pipe. With the extra capacity of the header and radiator, it took just under 9 litres. Started it and let it idle, took around 10/15 mins to get up to temperature. It also managed to keep the temp at a good number (93). Thermostat opens and the bottom hose got warm.
Went for a drive and car temp was good, it kept within 90-93. Will check in the morning at the header tank level and will top up if needed.

I'll give it a couple of days and get back to you guys, cheers for the advice and help.

​​​​​

Don Clark

If your header tank cap is working correctly it should still be full, having drawn fluid from the expansion tank as the engine cooled down.

siluro

The cap on header tank is a lower rating than the one on rad. The header tank cap has wings and the rad cap has none. The header tank cap is a two way cap, to suck the coolant back in as it cools. Rad cap only releases pressure.That's if they are oem caps. They must be the right way round otherwise this will cause temp issues.

My Hawkeye lets coolant get to 97 then fans kick in and it drops to 87. As described in manual. This is idling which takes 20mins plus. You say yours holds at 96 which is still not right. Is the thermostat opening properly, easy test once you got it out.

Brian Powell

Yeah, so I have the original radiator cap on the radiator (137kPa) and have the Mishimoto cap on the header tank (next to turbo - 1.3BAR = 100 kPa).

Reading some forums, there does seem to be a bit of confusion. I see some say that the header tank, as its the highest point in the system, that should have the highest kPa. While other people refer back to Fuji and state they say the radiator should have the highest.

An update -
2 days ago... I emptied it and refilled it via the turbo pipe like suggested. I tested it after filling up and it worked great. The bottom hose got hot. The car reached temps of 95 and then went down to 91 by its self. I took it for a drive and when boosting it does cool the car down a bit. (If overheating when boosting I'd be even more worried!)

But today I drove a bit longer and had to stop as the temperature went to 97 and I wasn't even stuck in traffic. Pulled over and opened the bonnet, there was a slight smell that smelled like the engine was hot. Checked everything all pipes were on, the expansion tank was below low, so I filled that up halfway (on markings) and checked the bottom radiator hose. It wasn't hot!?

So now I figuring out how one day it can work fine and the next it doesn't. One day the bottom hose and bottom of the radiator get hot and the next it doesn't.
Possible air leak? My Y connector pipe going to the radiator cap is a bit of a squeeze to get on... and I imagine when the system cools, if there was an air leak there it would suck in air... Maybe i've just answered my own question??

siluro

No confusion: The highest rating cap should be on the Rad 137 kpa. This rad cap will only release pressure and is a one way valve. OEM cap no wings. The cap on the header tank is a lower rating 108 kpa (by memory) and is a 2 way valve, OEM cap with wings.

You can inspect these caps and see which is one way and which a 2 way valve. As engine heats up it (header tank cap hence lower rating) allows the coolant to expand and dump the excess into the overflow tank front left next to radiator. When engine cools this cap allows the water to be sucked back into the system so has to be the 2 way cap. The rad cap is a safety valve and will only release if the pressure is too high for the system

The overflow tank should rise and fall with engine heat. When engine is really hot you will smell the coolant as the overflow tank is not air tight by design. If the the overflow tank overfills then you need to start to worry, as this is probably HG gone bad. You could also check that the hose going into the overflow tank is not getting blocked, dirt etc has been known to block this. To help with this take hose out and cut the end at an angle so it cannot be blocked so easily or get sucked to the bottom of the tank sealing it.

If you have an air leak then the level of the overflow tank will not drop when cold as the vacuum cannot be created.

Did you bleed the system after the refill. Youtube vids on this. I use a funnel stuffed in the header tank so I can see water rise and the air coming out. This whole process takes quite a while, I would at least let the cooling fans kick in twice before putting the header tank cap on. When filling did you leave the rad cap on cause you should. Keep at it, these are notorious at getting trapped air in them.

Last time it took me 2 goes but the first fill was just water (in the summer) just to give it a bit of flush. This first fill got a massive air lock and the temp with fans on just kept rising. I let it cool and turned the car around on the hope that the air would get dislodged (bumped it gently on the curb a couple of times for good measure) and rise to the top when bleeding, which it did.

Good luck.

Brian Powell

Getting late and I'll reply fully to your message tomorrow, but I'm looking into bleeding the system. I've seen they use these. Know anywhere in UK which sells them cheaper?

Or is that the going price?

Cheers