Just put a EJ257 in my WRX. Origionally 2.0 but now a problem with cooling.
Before the swap the temp reading on the hand controller would be a constant 86 after warm up. If idling for some time it would creep up to 91, fans would cut in then drop back to 86 no problems at all.
On initial start up after install, the car went to overheat straight away. I checked the thermostat which was NEW and it did not open. Tried the car with no thermostat and all was ok as original. Bought another thermostat, checked before I put it in and was working.
Now the problem. Car warms up as it should but increases past the 91 fan cut in point and goes up to 94 with fans contantly on.
I have had it idling for over an hour and it does not pass 94 or boil over at all. If driven the temp will sometimes drop to 92 but be more or less stay around 94.
Went to cheam motors to see if the CTS was different from the 2.0-2.5 and it was. They couldn't tell me if it was different on the temp reading so I ordered one to try it. Unfortunately it is a totally different connection so unable to fit. New one three wire and old two wire plus different plug.
Obviously I can run the car without a stat in it, or one with extra holes drilled in it but the problem I have found is that it runs to cold under normal driving IE: around 50-55 and the choke seems to try and keep coming on.
SORRY FOR THE LONG POST EVERYONE but any help would be appreciated as I am baffled by this.
Thanks in advance.
Del

 

very strange what happened to the old 2.0? if the head gaskets went or it was damaged may be worth looking at the water pump (i know most people change this when a problem like that occurs) just a thort i(im not a specialist have you thought of calling scooby clinic or zen performance two companys that offer 2.5 liter conversions?

 

I did fit a new water pump. The old 2.0 coolng was spot on with no probs, reason for change was broken ringlands. Just seems odd to me that the 2.5 is running hotter. I will speak to one of the tuners, just thought I would throw the question out to the scooby massive as there is a wealth of experience and knowledge here!!!!

 

Have you tested it in water to see what temp it opens at,, might not be opening untill 94.

 

Yep started with cold water on hob, digital thermometer in water. Started to open at 75 and was fully open at 80. Stamp on the stat says its 78 so I suppose thats close enough.
Tried this twice and on both attempts the opening times were within a few degrees.

 

Weird, as you say it runs fine without a stat in there, I'd try another one and see if it does the same,

I wouldnt of thought it would be anything else,, I've been a mechanic for 18 years and really cant see any other problems that would cause that, other than a blocked rad?

 

I though it could be rad related so flushed and reverse flushed, thinking it may be partially blocked and that the 2.5 may run hotter than the 2.0. No joy with that one, thats why I am puzzled as I thought I had covered everthing it could be, including doing a sniffer test even though they are new headgaskets on there.