Engine heating up then dropping back down?!

kris_aka_edu · Post by **kris_aka_edu** » Sat May 25, 2013 10:46 am

Yeah well got a brand new thermostat I could you find me both the sensors on eBay and copy a link for me to have a look? 92 4th gen 2.2. Would be a massive help. As for the wiring I don't have a meter to do it and wouldn't know how to do it any way.

Post by **DaveyBa8** » Sat May 25, 2013 10:51 am

Why put a new thermostat in without testing it first in boiling water? Make sure you have bleed the car and the rad is full to the brim, there is few things that cause a car to not heat up, stuck open thermo, needs bleeding. If your getting no heat through the cabin I doubt its any sensor.

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Sat May 25, 2013 11:05 am

You should find the sensors are easy to get from a local motor factors, I've done that before no problem. They might well not have in stock, but will be able to get easily (next working day) and they'll be able to look it up in their sensor suppliers parts books.

It's the same sensors as used on some of the engines in Rovers (2/4/600s) of similar vintage, hence it's pretty easy to get hold of.

I'd test them before forking out money on them first though, definitely.

kris_aka_edu · Post by **kris_aka_edu** » Sat May 25, 2013 1:13 pm

Yeah exactly what happens. Round town heats up a little bit and then get on the motorway and it says engine is cold. No hot air in the cabin. I tested my old thermostat before putting the new one in and it barely moved at all so you could tell it wasnt working properly. I haven't bled the system yet. Could you give me a quick guide on how to do this? Although its a brand new radiator a few weeks ago.

kris_aka_edu · Post by **kris_aka_edu** » Sat May 25, 2013 1:18 pm

I'm not going to buy anything now unless I can definately work out that's what it is. Wurly hopefully if you can make it round Monday you'll be able to give me some advise and see what you think!

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Sat May 25, 2013 1:24 pm

If you haven't bled the cooling system, that's definitely the very first thing to do.

Make sure the heater is set to fully hot. If you have the JDM I think that means you need the ignition/fan on (otherwise it doesn't operate the coolant valve???) if UKDM, just put the heater slider onto hot no need to put the ignition on.
With the engine cold, top the rad up fully, then undo/open the bleed screw on the thermostat housing.
Coolant needs to run/spurt out without being bubbly. If it doesn't, pump the rad hoses until it does (keep the rad topped up as required).
If that doesn't help, you can loosen one of the hoses attached to the idle air control valve (on the inlet manifold) and bleed from there.
Once that's all good, close up the bleed valve/refit the coolant hose on the idle air control valve, make sure the rad/expansion tank are properly topped up, start the engine and let it warm up to normal operating temp (fans come on). Then stop it and re-check the bleed valve (careful as it's hot). Should get coolant spurting out, no air.
If you get air you need to bleed again, otherwise if it comes straight out as coolant then you should be

Yep, keeping Monday free.

kris_aka_edu · Post by **kris_aka_edu** » Sat May 25, 2013 3:12 pm

Jesus that sounds complicated!! Got no fans as they where broken and so they didnt go on my new rad, it's something I'm looking out for. Ill ask a mate for a hand shouldn't take long. Hopefully?!

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Sat May 25, 2013 3:51 pm

It's not as complicated as it sounds.

kris_aka_edu · Post by **kris_aka_edu** » Sat May 25, 2013 3:58 pm

I'm round a mates house near me now, he said he knows how to do it. So will give it a go in a minute. I'll let you know how it goes, but he doesn't think it will make much difference as we had the thermostat out yesterday and then squeezed the hoses with the cap off and then topped it up. Just didn't use the nib.

Wurly i'll give you a text later about Monday mate. Can't wait to get that new ECU in with a working rev counter! Will need to take out the traction control light though

kris_aka_edu · Post by **kris_aka_edu** » Sat May 25, 2013 5:45 pm

Right. I've just done a whole bled of the system. There was lots of air coming out of the nib. So decided it would be best just to dump the whole lot out and start again. So filled it back up and then undid the nib so it squirted out better, although still its bit bubbly. I've taken it out for a couple of runs and now its heating up to a quater, and not the minimum. It did reach full temp for all of 10 secs then as soon as I put my foot down it dropped right back down again. I don't know if there is some type of air leak or something. The hoses are fine, although they are the original black hoses. I also made sure the expansion tank was at the right level. My mate owned a prelude for 9 years and even he said hes run out of ideas. The engine after a good long run was still touchable, I thought it would be too hot to touch?! Does this mean that the actuall engine itself is not heating up properly?!