KZN130 - she's let me down!

[solidpro]

Hi All

Wonder if anyone can speculate on my problem. I noticed this morning I suddenly wasn't getting any heat into the cabin through the blower. All was fine yesterday.

On my way home I noticed the engine temp getting dangerously high. Randomly I suddenly would get 30 seconds of warm air through the blower and the engine temp would drop before going cold again and the engine temp was getting dangerously hot.

Checked the coolant level and whilst lower than expected is still there and no escaping through a pipe or the exhaust.

I don't know much about engines but suspect the fact he coolant is retained and the blowers are cold disproves head gasket.

I'm guessing the coolant being there disproves a leaking pipe or radiator (new 6 months ago).

So what do we think? Could it be the thermostat has failed? I don't truely understand what a thermostat does...

I suppose the alternative is a blockage. It's not likely to be ice as the cold has t set in yet where I am (was not freezing overnight).

Any help appreciated. I'm a single dad who relies on the car to transport my two young boys...

Cheers

[solidpro]

I also put a bit more coolant in and watched under the car - no drips. I feel the clue is in the blower going hot very briefly and this 'fixing the engine temp'. For the rest of the time the blower is ice cold regardless of the setting.

The return pipe is not blocked as I can see coolant drilling through it back into the expansion tank.

I guess also it could be the water pump isn't working??

I'm 10 miles from home and now stopping every 2 mins to get the engine temp down to get it home!

[BUSHWHACKER]

Probably just an air lock in the cooling system.

When the engine is stone cold, set both heaters (if you have a rear heater) to hot and top up the coolant.
Make sure you're parked on level ground, if not posible park with the front of the truck facing uphill. Once you've topped up, leave the cap off for a few hours or overnight if possible, any air bubbles should have worked their way out by then.
Also, make sure the expansion tank is at least one third full.

[solidpro]

Thanks For the reply Bushwacker.

I didn't think a blockage was likely 'out of the blue' - I.e not related to recent works on the engine?

I do have a front an rear blower and once I get home ill let it cool and try it.

Should I have the cap off the expansion tank when trying it with the heaters on full blast?

I will try to elevate the front of the car if I can.

With my limited knowledge I still think the water pump may have gone. This is a car with 240k km on the clock and I believe it's the original pump. I've recently done the original batteries, rad, brake calipers and discs so it seems things are gradually expiring after long service....?

[BUSHWHACKER]

If you've recently had the radiator replaced, it's more than likely an air lock thats causing the heaters to blow cold air..

Top up the expansion tank first if it needs it and put the cap back on.

[solidpro]

Rad was replaced at least 6 months ago....

For what it's worth, the back blower is also constantly ice cold.

Still not clear if once cold and I run it up with both blowers on if its best to leave the cap off the rad or the expansion?

Thanks

[J i m s t e r]

Are you sure you're not losing coolant? The pipes that go back to the rear heater, under the truck, are notorious for corroding straight through, or getting porous enough to lose fluid.

[muddle]

You say you can see the coolant flowing so its unlikely to be the pump, start with the basics and try what bushwacker has said.

[solidpro]

Ok the plot thickens.

I've had it elevated at the front about 25 degrees, expansion tank lid off, running for 20 minutes now. The temp needle got to halfway and is staying there. Not overheating.

The front and rear blowers have been on full the whole time on hot and both remain ice cold.

So it's not overheating when stationary, blowers ice cold. What could it be?

Shall I leave it elevated overnight hoping it will burp itself?

We're gonna have a frost, but I topped it up with antifreeze earlier just to be sure...

Definitely no loss of coolant - it's sat there at a solid level the whole time. Went down slightly when running a short whole but not a lot.

[BUSHWHACKER]

Check the heater valve on the bulkhead is working (cable not come adrift) if all OK the the heater matrix could be gunked up.
The same same gunk in the pipes under the floor could also be preventing the rear heater from getting hot.

[solidpro]

I'll have a look for it in the daylight.

I thought the idea for clues with the front and rear blowers was that they were on pretty much different radiators etc.

After 30 minutes of it running, the temperature went up to 3 quarters. When revving her slightly she would go up more. Never went into the red, but even the slightest rev would push it up. Obviously if I tried to drive, it would very quickly go into the red.

Am I correct in thinking that if there was a problem with the head, I would lose coolant? I don't get it.

[BUSHWHACKER]

Ah yes yours is a 3.0, the rear heater pipes 'T' off the main coolant pipes near the brake fluid reservoir and go down under the floor and up into the heater unit. So they're on the same 'circuit' as the main heater.

On the 2.4 they are seperate from the main coolant hoses.

[solidpro]

But surely even if the blowers were completely blocked or inoperable, she still wouldn't overheat once being revved?

Never saw the fan come on either.... Even just below red.

[BUSHWHACKER]

Was the thermostat replaced when you changed the radiator?

Although if it was stuck open, the temp gauge would be reading low or at leats give a fluctuating reading all the time.

[TonyN]

Are you checking this at the rad cap? You keep saying expansion tank cap, the level in there has nothing to do the coolant level.