Got a irritating problem with the car temperature. I get hot air blowing in the car no ptoblems, until occasionally it will blow through cold whilst stationary.

I can't see any leaks anywhere. I've filled the radiator upto max, run the car upto temperature and made sure there's no air left in the system.

Yet if I stop the engine, remove the rad cap, there's little pressure and the water is only tepid at best.

The engine doesn't overheat, but has got upto 90° when it usually sits,around 80°-83°.

 

Any suggestions?

Forgot to add, when cap is removed, the water level has gone down by around a inch from top of radiator.

Car runs fine and doesn't seem to have gasket problems.

I use to get a similar problem and it was the rad cap, now I have changed it the water pipes go hard and have to wait a while before taking rad cap off.

Didn't build up enough pressure on idle to push through matrix.

 

Goodluck.

The radiator cap is brand new, it says 1.3bar. It came with the radiator I've got.

will try it tho and see if another one helps any. Cheers bud.

Could b a dodgy rad cap even if it's new worth a try.

If not it's worth getting it pressure tested for leaks should build up pressure and pipes should be fairly hard when warm maybe not big enough leak somewhere to see it leaking but enough for it not to build up pressure.

Check also that your rad pipe hasn't collapsed in on it's self at the bottom. Jeff put a post up about it a while back

Yep, good advice, the pipe that runs from the bottom corner of the rad, along the underneath to the other side of the car can collapse in on itself if its old...

i had similar on mine, after checking everything many times, i was at a loss, turned out to be the expansion bottle had a hole in it, caused by the traction rods not being set correctly and the tire had cut a thin slice in it.

As when the engine got upto temp, to prevent excess pressure it should dump some into the expansion, then when it cools it draws it back. but due to hole was losing it.

worth checking.

Checked hose and that seems fine.

I don't have a expansion tank on so no leaks from there,lol.

Gonna have to check the thermostat tomorrow and see if that's working all ok.

Hopefully we will get to the bottom of this problem.

Checked hose and that seems fine.

I don't have a expansion tank on so no leaks from there,lol.

Gonna have to check the thermostat tomorrow and see if that's working all ok.

Hopefully we will get to the bottom of this problem.

 

Did you check the hose with the engine running? iirc it only happens when coolant is moving through it.

Ye, had it running and upto temp, and gave it a few revs while checking it.

Ye, had it running and upto temp, and gave it a few revs while checking it.

 

aah, right. Not that then. Thermostat next then mate as you said.

 

Good luck with it :)

My stock gauge stays below half way, but my pod gauge is the one showing various temps. I'm assuming its cos there's a lack of moving water in the top hose. Could this indicate a sticky thermostat?

My aftermarket temp gauge has started doing something similar, but, my aftermarket oil pressure gauge started doing funny things first, it started twitching and going high, low randomly, so i though the sender might be duff, but then my water temp started going funny, in sync with the oil pressure gauge, so I'm thinking dodgy earth on the gauges...

i had the same problem after changing my thermostat, but for the money get a new thermostat and change that. the reason your getting cold air on idle, is the water flowing back into the system, i know you said you dont have air in the system, but a cool blower when the temp is set to high, is indicative of air being trapped in the heater matrix, with the car up to temp and idling, undo the matrix pipes at the rear and see if you are getting flow, you dont have to pop the pipes off, just undo them enough to get them to leak. do one at a time, this should show if you even have enough water reaching the rear pipes, if you are getting flow to the matrix, then id say its the valve in side the matrix not opening when it comes up to temp, thus no flow through the matrix. if you are not getting flow through the pipes then the problem is engine side.

 

If you havent done so yet, get a block tester kit, you still might have a small head gasket problem and a block test will highlight this.

 

Also quick and easy, bring the car up to temp, give it a bit of throttle on idle, and get under the car, have a look or feel for the lower rad hose, if its collapsed it could be a radiator blockage like mine was.

 

Next up would be flushing the system, you want to start with the cheapest options first, so get some Demineralised water and some unmixed coolant (well unless you like the premixed stuff) drain the system fully (there is a block drain plug just up behind the A/C compressor to empty the engine. Once the engine is empty get a hose pipe and get it flowing through the engine with some force (best done when changing the thermostat) also remove the two matrix pipes and flush hose water through them both ways, you will be surprised how much crap comes out of both of them.

 

Put it all back together open the overflow bottle cap, and top up to half way on the levelling stick, then top the system up, it takes about 10litres from a completely empty system. so 5lt of water, and 5lts of coolant (well that's what ive got, i know you can mix and match depending on the weather) bring the car up to temp with the rad cap off and wait for the thermostat to open, this should allow you to put more coolant in. leave it idling until you cant get any more in the system.

 

Another good idea is renewing all the coolant pipes, you might find like i did, that they need renewing, when the system cools it can suck air in through age cracks in the pipes, the cracks are large enough to let air in but not water out.

 

HTH's