Engine heating up then dropping back down?!

BMCC · Post by **BMCC** » Sun May 26, 2013 5:50 pm

Did you replace the rubber seal on the stat?

kris_aka_edu · Post by **kris_aka_edu** » Sun May 26, 2013 8:25 pm

Yeah it came as a kit. Found out the thermostat housing was leaking so I sealed it with high temp water resistant quick gasket. Now the rad cap is leaking as it doesn't actually fit my new radiator! How annoying!

BMCC · Post by **BMCC** » Mon May 27, 2013 9:56 am

Hopefully a new cap and your on your way

kris_aka_edu · Post by **kris_aka_edu** » Mon May 27, 2013 10:33 am

Crossing my fingers and hoping it is just that left now!

Riverghost · Post by **Riverghost** » Mon May 27, 2013 4:24 pm

just adding i was having similar problems to this, a good bleed of air out of the coolant system seems to have rectified this, and temps hanging at 1/2 way constantly now. sure there is still some air left in the system though as the top hose gets solid as hell after just a few mins of running

kris_aka_edu · Post by **kris_aka_edu** » Mon May 27, 2013 7:05 pm

Just been with Wurlycorner all day who made the effort to come down and see me and... After a good 6 hours of working on the car we realised that the thermostat I was supplied from my local dealer was the wrong size so it was letting all the water past! So now need to get the part changed then after a good two weeks of working it out I will have heat In my engine again!!!

kris_aka_edu · Post by **kris_aka_edu** » Mon May 27, 2013 7:06 pm

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Tue May 28, 2013 1:44 pm

Yep, not been online to catch up with posts since Saturday, just dropped in quickly now to update here...

So Edu had bled it all properly before I got there - no problems there.
The new rad had come without a cap and the rad is different to the old one so I could see the original cap wouldn't fit properly. (The core on the new rad is also thinner than on my vtec's so I'm guessing it's off a 2 ltr, but I doubt that'll cause any problems tbh.)

I took a load of measurements from the rad neck on the new rad and we went off to a jap breakers nearby and managed to identify a couple of possible caps. Bought 3 back and the first one fitted perfectly.

Ran it up to temp ok on the driveway, re-checked it was bled ok and everything was hunky dory, went out for a drive and it was just as Edu described, the temp dropped down as soon as you got up to any speed.

That could only leave both sensors being knackered, or thermostat fault as far as I could see. I'd checked what readings all the sensors were giving earlier and they were all comparable with mine, so they're fine, so it must be the thermostat opening too early (possibly the wrong temperature stat?)
Took it out to check what temperature stat it was, but there was nothing stamped on it (normally stamped on the body, as it was on the old one)

Decided just to watch how it operated, so Edu boiled the kettle and whilst he was doing that, I rang Hardy, just to check if he could think of anything else (I just found it hard to believe that a new thermostat could be knackered tbh and thought surely I'm missing something?!). He agreed with me and while I was on the phone, I idly dropped the old stat into the pot of water and suddenly BINGO! This was the first time I'd seen them next to each other and could now see the old one was bigger diameter.

I can't believe how unlucky Edu's been here - he's been sold the wrong stat. It's too small for the recess that it's meant to sit in at the front of the housing, but doubly unlucky, it is the SAME diameter as the ID on the main thermostat housing, so when you push it in, it DOES actually sit tight and feels like it's meant to be there! The only difference is it slides in too far and so it won't block the flow and will instead act as a partially open stat at all times.

So just a case of tracking down the right one now, fitting that, refilling with coolant and bleeding and then should be all sorted

We got the other thing sorted with the Spoon 3 pin ECU too - will update the other thread.

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Tue May 28, 2013 1:57 pm

Anyone know anything about there being 2 different sizes of thermostats fitted to preludes???

kris_aka_edu · Post by **kris_aka_edu** » Wed May 29, 2013 1:54 am

Absolute legend. Brilliant meeting some one off the forum and a genuine nice guy. I'm picking up the new thermostat tomorrow. After all the working on my car (a mere 5+ hours) I gave him my old ECU. A small price for someone who has put so much effort into my car. Can't say how much I appreciate his work and effort. Will update this thread tomorrow hopefully with all the good news I've been after for two + weeks!!