Having a pew problems with over hearing on my v1 sti first my top rade hose is hot and the bottom is cold will drive fine then temp gauge starts to rise and fall and bubbling our of the overflow tube with yellow cap any ideas hoping not head gasket and was thinking thermostat
Any help guys

 

Airlock? Check on here on how to fill without airlocks.
Thermostat? Cheap to replace but you can test yours if you take it out.
Head gasket? Get a sniff test done

 

Had the bubbling from the overflow on 2 of my classics - sadly was hg failure even after a stat change and a burp. Get a sniffer test done asap

 

As above, sniffer test first.

Had any work done on the cooling system recently?

 

If it does it more when boost is used it is probably HG.

 

Done a 30 miles drive mixed driving not a problem then starts again feel bottom rad hose and cold top is hot what are chances it's the thermostat

 

The bottom hose will always be cooler as that's the rad doing it's job - putting colder water into the system.
I've just sniff tested my 07 STi, same bubbling. Struggled with sniff test, the detection fluid kept staying blue.

Anyway, gave it a real good boost in 4th and 5th gear, got home, bubbles in the non pressurised overflow tank.

Managed then (just) to get the sniff test dye to turn green, not yellow.
Good enough for me, my HG's or at least one is shot.

Black bits it the coolant, like thin tiny bits. It's the sealant from the HG.

Rebuild time for me!......oh well, a built 2.5 will make a cracking road car, so in that respect I'm pleased that I actually have a good reason to get it done.

Ouchy on the wallet though lol

 

the bottom hose is cold then other times hot so I'm not sure if theremostat is some times not opening

 

Am I right in saying the thermostat is where the bottom rad hose connects to

 

Please............do you READ any replies?


If the thermostat stops working, the WHOLE ENGINE runs cold.

 

Yes it's in the waterpump housing connected to bottom hose.

I would of thought if a thermostat is stuck shut it would make an engine run hot not cold?

 

Did you sort it?.

 

99.9999% of the time they stick open. it's a failsafe thing, so as not to destroy your engine.

A failed thermostat almost always means the engine doesn't reach temperature.

 

Just to say on one of my scoobs someone before I owned it had put it's thermostat in backwards so the constant flow of water pushing against the thermostat eventually jammed it shut, killed my engine