No overheating but bottom rad hose cold
 

Guys - please don't jump to headgasket - yes there is a possibility it is but please try and give constructive feedback thank you!!

I recently put an OEM thermostat back in car and filled with coolant and a full bottle of water wetter.

Had the car out several times shortish journeys and car gets up to temp fine. Temp gauge stays solid on half way mark at all times - idling or driving. Car runs like a dream with full power and nice idle.

What I noticed today that the bottom hose is stone cold and small bubbles from expansion tank.

I am not losing any coolant, I bled the system the correct way and filled up using the back turbo coolant pipe.

Just looking for your honest advice here - I am confused as the car temp stays solid and heaters are roasting at all times.

The radiator felt v hot at top hose end but cold as it progressed to other side - strange

I have recently done several head gasket tests using the coloured dye and nothing came up - over several attempts.

Should I refill coolant once again lol

The journeys have been short -as I said about 10 mile round trip

Another thing to consider - under full boost the temp gauge drops for a second then rises back to half way

I did have my waterpump replaced when I bought the car (but you just never know if they actually did it or stuck a cheap one in)

One last thing - the bottom hose usually is warm - certainly prior to doing coolant change.

Could this be waterpump cavitation, air lock, water wetter working extremely well or yes the head gasket lol
Thank you in advance

run it up to temp with the expansion tank off , you don’t want the expansion tank full as it will bubble over , bubbles not a good sign , hg you normally get over heating or you will find the non pressured expansion tank fills up and when the engine is hot and when the engine is cold the water does not return to the engine , if you take the pressured expansion cap off when it’s cold , the level looks full but as soon as you start it the level drops down , could be a faulty thermostat even if it is new , maybe water pump but less likely , the bubbling into non pressured expansion tank is that all the time or for a while and it stops , if all the time it’s either bleeding air out or air is being introduced into the engine as it’s running ie head gasket , the sniff test did not work on mine even when hg had gone

Cheers mate - brilliant info.

I didn’t think the bubbling is all the time abd the water level does rise an inch when hot then fall again back to full mark when cold.

The radiator was awfully cold across 3/4 of it. Never seen that before - and never seen bottom hose remain cold

try what i said about bleeding it , cap off when cold sometimes helps pointing up hill and see how you go , sometimes if it’s a hg may only do it when driven and hot , the fact the non pressured cooling level is returning to normal is good , also when bleeding it put heating system on full hot with blowers on , fingers crossed you did not bleed it very well , is it a 2 or a 2.5 engine , if it’s a 2.5 bit more prone to hg issues

2.0 gc8 sti v3 sir - thanks for al advice. I guess I will need to remove all coolant and start again?

All very strange mate, thanks for the advice - ill do coolant again and take it from there - nigthmare !

no need to remove the coolant , when cold expansion tank cap off, and drain a bit of coolant out of it , start the car heater on full and go from there , stick with it till it heats up , you will see a lot of bubbles in the pressured expansion tank so in effect it’s bleeding itself , i will leave cap off as long as i can , good luck ,

Top man, Turkey baster will be getting used tomorrow!
Thanks. Ill update tomorrow afternoon!

no problem , once there is no more bubbles in the pressured expansion tank top it up put cap on

Seemed to work a treat mate! Let it cycle twice through fans then topped up. Bottom hose went hot before first fan kicked in.

Got some videos of header tank when idling but looked fairly calm, other than level rising as it heated up.

Can i I upload videos here ?

Thanks very much !!Saved me removing thermostat!

no problem , sounds like things went well , non pressured expansion tank should fill and go back down to where it was when cold , a bit of bubble is ok in that tank if it’s a lot all the time and tank does not return to normal level when cold you have issues , take it for a good lol run and it should all go back to where it was cold

Ha ha will do! Do you have a gc8 ? Always scared to continuously nail it in case it blows up lol.

When hot expansion tank rises about an inch then drops when cold - that sound about right or would you expect to see more movement?

thanks again!

i have a few forester sti , only nail it when warm , an inch is normal for movement

Cheers mate!

no problem sounds all good just test it by giving it a good run , it does just sound like air in the system

I man pretty certain my header tank has a leak at the neck welds. Could this possible draw air into the system?

they do fail sometimes , it’s more likely to leak coolant under pressure and as it does not hold pressure a vacume is not created so coolant is not sucked back from the non pressured expansion tank

i take it it’s all going well ? no more issues ?

Sorry for late reply !

Yes all going well.
She doesn’t really get fully warm until I give her a little stick - even after 11 miles! Bottom hose remains cold until I start to push her above 3k revs.

Car engine gets up to speed before that point but bottom hose and that side of radiator remains cool.

But she does get up to temp when being worked and does not drop a spot of coolant.

Temp gauge staying bang in middle which is good. It does drop the temp when booting it at speed but return to center quick enough. I just think it is part of having an old car as a lot of cold air passes the radiator and so on.

Running best it ever has - would fully recommend water wetter. Really does lower the operating temperature dramatically!

Still want to replace header tank just in case though!