1.8NZ possible overheating ?

[GLC]

Had a bit of a ongoing issue and not sure what my next move is, so hoping somebody can point me in the right direction!

My Cavalier since I've started driving it daily the last few months has developed a habbit of getting hot when stuck in traffic.

When driving along it seams fine temperture wise. Soon as I get stuck in some traffic the needle shoots up and the fan kick's in and only once I get moving again will the temperture drop down back to normal. Turning the heater up helps when stuck in traffic, but not enough to bring it down to shut the fan off till I'm moving again.

Replaced the Themostat about 4 years ago with a GM item after having a similar fault before which was caused by this failing which is somthing I'm keeping in mind.

So I Replaced the Fan switch with a GM item about a month ago on the off chance and tried replacing the temp sensor for the gauge for a none GM item. But the gauge sensor just made the Cav run hotter and stay in the red! Cleaning the original one and refitting it brought it back to normal or so I thought.

The coolant level hasn't dropped either during this time and can't see any sign of water and oil mixing.

The Engine done around 220,000 and was brought as a secondhand replacement 9 years ago with only 140,000 and as far as I'm aware hasn't had the headgasket changed. The Cav itself is on 197,000 as of yesterday.

So before I start trying to buy parts I may not need, can anyone advice me on what best course of action to take?

Cheers.

[ilovedmymantas]

Hi,
first of all congratulations on the major mileage!

hopefully your in luck and It's (almost) a free fix. I've had this with successive cavs and replaced the parts that you have, mostly with no improvement.

The culprit has almost always been an air-lock in the coolant system. Wish I'd known
It was obvious on one occasion when I could hear a gurgling sound from the dash area when 'wellying' it.
My thinking is if there's an air-gap, so the water's not flowing continuously, steam will be produced raising the temperature.
I would reverse flush the system with a hose. That will clean out the block and radiator.

More importantly disconnect the heater matrix hoses and reverse flush it. It's often overlooked.The matrix is the highest point in the system so that's the most likely place for an air-lock I figure. I was amazed at the amount of crud that came out of mine each time, and the sediments caused by the air-locks aren't good for flow.

Top-up all the disconnected hoses with water before re-connecting, starting with the lowest point.
To minimise introduction of air to the system, add some water slowly to the expansion tank (work out your mix of coolant to water) and add coolant after. I prefer around 60% .
Start the engine. When the level drops, after the thermostat's opened, add the coolant, again slowly, and let it mix.
After doing this on 3 cavs My temp gauge shows 96 degrees when hot

It's been a problem common to all my cav's so hopefully It'll help

[Cavalier342]

I agree with the above, try a simple flush/drain/flush/drain, both ways, i.e. from both sides of the radiator, and inside the radiator in case there's some sort of blockage. While she's warming up, feel the big hoses which run from the engine to the radiator, sqeezing them every now and then to get the bubbles out, you'll see the bubbles come up in the coolant reservoir, make sure the cap is off it. Keep sqeezing them slowly every few seconds until no more bubbles come out then let it get hot and the fan kick in, it it starts overflowing from the reservoir, then there's still air in the system, just turn it off and carefully screw the cap back on.

[Robsey]

Just a minor addition to that.

I have found that if the cap is off and the engine is hot -
The header tank will probably over-flow quite significantly approx 10 to 30 seconds after you turn the engine off.
The level will rise steadily and just over-flow.

In my experience, it is just residual heating of the coolant trapped in the engine block, and so nothing to worry about.

(There are no air bubbles if the system is free from trapped air ).

After topping up or changing the coolant, I often give the fat hoses on either side of the radiator a firm squeeze, as this displaces air effectively from the system.

And as a paradox - if the coolant level is low, the cabin air blowers will intermittently blow cool air out of the vents, when there is air passing through the heater matrix.

Again, top up and firm squeeze of the fat hoses usually solve this.

[iangsi]

My 1.8 runs hot but it has never overheated, the gauge on the dash barely gets over the quarter mark before the fan cuts in. I've put a new water pump in it & no difference, flushing however did help as I was getting no hot air out of the heater,

[GLC]

Thank's everyone for the advice and cheers ilovedmymantas. It not doing bad for a car that only cost me £250 9 years ago. Am looking forward to seeing 200,000 on the clock even thought the engine done more of course.

Never did I think that I would still have my Cavalier 9 years later, as I've had cars just a few months when I was younger. It been a great all round car and I'm glad I got the chance to keep it on the road after it needed welding as it's repaid me more times than I can remember.

Will try and have a go at flushing the cooling system out and take it from there!

[GLC]

Spent yesterday afternoon flushing the cooling system through as advised. Pleased to report that this has made a massive improvement! Seams like it close to being about right again which is a relief being stuck on the M42 this morning. Will keep an eye on it over the next few weeks and if needs be will flush through again.

Thank's everyone for the help.

[Cavalier342]

Glad to hear it.

[Robsey]

Yep -
Glad to see Andrei has helped you get it sorted.

Well done chaps !!

[ilovedmymantas]

Good that you've got it sorted, cheaply and easily
Was there a lot of sludge? Mine looked like it was pumping out mud

[Cavalier342]

Yep -
Glad to see Andrei has helped you get it sorted.

Well done chaps !!

I can't take all the credit for this, as others have made their input as well.

[Robsey]

Yep -
Glad to see Andrei has helped you get it sorted.

Well done chaps !!

I can't take all the credit for this, as others have made their input as well.

This they did, but you were the first to encourage a flush of the pipework.

Usually the last thing that I would think of - ha ha. Far too sensible for me.

[Cavalier342]

Yep -
Glad to see Andrei has helped you get it sorted.

Well done chaps !!

I can't take all the credit for this, as others have made their input as well.

This they did, but you were the first to encourage a flush of the pipework.

Usually the last thing that I would think of - ha ha. Far too sensible for me.

Well the only sensible response to that would be that I liked to keep my pipes clear And just to be a bit technical, ilovedmymantas suggested it before me