Strange cooling problem

[chimhunter]

Bit of an odd one this one. The symptom is that after running for a while (like more that 30 mins) the temp. guage suddenly drops to 50-60 deg. C and refuses to come back up. The engine is still hot so the guage is definitely lieing to me. After letting the car cool, its fine again until the next 30 minutes.

I had the rad replaced at David Batty a couple of months ago so it could be related to that, like an air lock? Any other ideas? Thinking of getting some engine work done in the New Year but I need to get some sort of idea if its engine threatening or not and so treat it sooner...

Rob

[pigpen]

Hi Rob

Not had quite the same symptoms but it sounds maybe a combination of airlock & thermostat sticking open. A couple of times I have had the swirl pot develop an airlock in the top and push water out of the reservoir. Even if the reservoit looks ok, say about 1/2 full or so, check the swirl pot & top up if necessary. 'Course I could be a mile off!

Cheers

Mike

[chimhunter]

Thanks Mike, I'll check.

What were you doing up at 3am? Or shouldn't I ask

Rob

[david beer]

Sounds like the sender, mine did exactly the same,i used the spare sender on top of the head.Its a single 4mm round connector, use a variable resistor to calibrate, saves doing what is a real pain to replace. Many have done the mod, not all cars have it, but worth a look !

[chimhunter]

David, I don't suppose that's in the bible is it? I'll have to check tonight

Thanks for the info

Rob

[kevp]

Im trying to remove my rad at the moment (posted on site).I discovered that the water bottel was full but the radiator had no water.

I assumed there was an air lock between the bottle & the swirl tank. what had happened is the alley nipple that the hose is connected to had corroded solid and needed drilling out before any coolent could reach the swirl pot.

[pigpen]

Hi Rob

In the Gulf at the mo, hence time difference. If I'd been up at 3 it's highly unlikely I'd have been on here! How did you get on with your problem?

Cheers

Mike

[chimalsu]

had sim problem myself,gauge would register for so long then just drop to 50-60,sometimes jumping back to normal then dropping back again.bled system many times but no improvement,checkedtemp with infrared and showed ok,removed the sender connect and copperslipped and it read ok but since doing 1000m in france now reads steady but 20deg low ie runs 60ish fan cuts in at 70 so this i can live with. wondered myself if that brass unit with like a brass barrel connect could be used as a temp sender any spacific resistor needed

[chimhunter]

Thanks. I'll probably get around to looking at this at the weekend. Sounds like the most likely thing is the sender. I'll check and let you know how I get on...

[david beer]

Usually a 120 ohm resistor is about right, but can vary so best to go for a heat resistant variable. Email me for details of where to source.