AU Series 1 using too much coolant

[webbiegareth]

Hi all,

My other half picked up her mother's car... they bought a new car so we're taking their old '99 AU Series 1 (i6) sedan off their hands.

The thing is using way too much coolant - in one day it'll go from MAX to under the MIN mark so it needs constant topping up. I'd wondered why her mum had left big bottles of water in the boot!

The first day I didn't notice a leak anywhere, so I figured it was internal usage... (i.e. gasket problem), though the oil level is still at the FULL mark, and it looks nice and clean - so the car doesn't seem to use any oil, just coolant.

Yesterday when we drove it to the shops (the overflow bottle was FULL that morning), getting it back I popped the bonnet and noticed the coolant (well, water I guess) in the overflow bottle was bubbling and boiling (you could really hear it boiling), and water was escaping via the little black overflow tube that comes out from under the radiator cap.

NOTE: It was only bubbling in the 1st plastic bubble, where the top return hose is coming into overflow bottle - it was really putting a lot of water into the bubble which is why it looked like it was bubbling and boiling. The main "bubble" (with the big radiator hose coming up from the bottom) wasn't bubbling, it was just rising up and down as it pushed water out the little black tube.

I left it like that overnight, and checked in the morning (today) - it's now just a bit above the MIN mark.

I'm assuming this is why it's loosing so much coolant...

What causes this, and what should be done to fix it?

[Bushbasher]

Sounds like it's done the head gasket. The gasket has only let go between the cylinder and water jacket somewhere so it's pressurising the coolant system and pushing the coolant out.

[SirHenry]

G'day,

I'd be getting a pressure test done to rule out a head gasket, they are rather hard to blow in an AU but not impossible.

I'd be looking for white marks in and around the engine bay and on the garage floor (coolant dries white). That much coolant must be going somewhere so it should be showing up somewhere around the engine.

Definitely a leak somewhere in the cooling system, take it to a radiator specialist or your trusted mechanic.

Good luck and I hope it's not too expensive.

[Beer Baron]

Common water leaks on AU's are:

Head gasket leaking into oil, cylinders or down the side of the block
Welch plugs.
Water pump o ring.
Thermostat housing.
Split radiator.
Heater tap/hoses under the inlet manifold.
Worn water pumps.
Auto oil cooler split and coolant running into the auto.

A head gasket is time consuming for the home mechanic but reasonably easy. Welch plugs are easy except for the one inside the gearbox bell housing as you need to remove the gearbox to replace it. BTR auto's are not a light gearbox.

[FAT245]

Originally Posted by Beer Baron

BTR auto's are not a light gearbox.

Tellme about it, i had to carry a greasy box up my driveway...

[mik]

if it`s been running on plain water for a while because mum has had to top it up due to leakage somewhere, the head might be damaged, alloy corrodes without corrosion inhibitors, i`d go along with what sir henry said, good luck and welcome to aff.

[mongrelEF]

You can check for compression by starting the car with the rad cap off and placing your hand over the hole.
Also the rad cap may have a weak spring and require replacing.

[webbiegareth]

Ta guys, I'm hoping it's not a head gasket! My mechanic is fitting new rotors & pads shortly, so he said he'll take a look at the coolant issue while he has the car. I had a look at the service history and it's been noted for the past 100,000km's that the radiator is corroding but it looks like they never did anything about it (!!!).

It really does look like they've been running it on plain water and that there's a bit of rust in the coolant (either that or oil, but the coolant looks a bit dirty and to me it looks more like rust).

However I did note that the rad cap was able to "rock" around a bit too much and was very easy to take on & off, so I bought a new one this morning which is a MUCH tighter fit (really had to push hard to get it on)... we drove it around for a 1/2 hour and I'm not seeing it overflow like I did yesterday. I doubt the rad cap replacement has fixed it though, I'm not that lucky!

The thing is, the engine idles very smooth, and the car itself drives very well and the engine feels smooth when I accelerate etc... so it doesn't feel like there's any damage to the head.

But it really does seem like I should replace the radiator and have the system flushed once we figure out what the coolant loss issue is (assuming it's not just the rad cap).

:( Bah... cars!

(We don't want to spend too much as it needs new brakes, the high pressure power steering hose leaks, there's rust under a door sill, the window tinting is badly bubbled and needs to be removed... all that needs to be done before we can roadworthy it)

[mongrelEF]

Originally Posted by webbiegareth

However I did note that the rad cap was able to "rock" around a bit too much and was very easy to take on & off, so I bought a new one this morning which is a MUCH tighter fit (really had to push hard to get it on)... we drove it around for a 1/2 hour and I'm not seeing it overflow like I did yesterday. I doubt the rad cap replacement has fixed it though, I'm not that lucky!

I'll bet that's what it was then! Agree you should definitely at least flush the system and look hard at the radiator.

[SSD-85]

By far the most common cause of coolant loss in an AU is the reservoir cap. They degrade over time & become more and more loose. Fortunately for us AU drivers, its without a doubt the easiest & cheapest fix.

Hopefully thats all it is with yours

[FAT245]

Scotty, i found that with my AU, replaced it then other issues arose (blocked radiator and cracked thermostat housing!)

[Road_Warrior]

Originally Posted by webbiegareth

I doubt the rad cap replacement has fixed it though

You'd be surprised, if the radiator cap spring was weak or of the incorrect rating, the cooling system will force all the water out as it pressurises.

[SSD-85]

Originally Posted by FAT245

Scotty, i found that with my AU, replaced it then other issues arose (blocked radiator and cracked thermostat housing!)

Im not saying other things arent possible, my XR8s radiator was leaking along with a shot reservoir cap. Im just saying that thankfully for AUs its mostly just a shot cap. My current Forte & Fairmont are prime examples of this.

[FAT245]

yeh, it was the first thing my mechanic checked!

[webbiegareth]

Thanks everyone... I'm 99% sure it was the rad cap. We took it for a 200km drive today to test it out (out to Torquay to the beach), and after gettting home and letting it cool down... the coolant level is still pretty much the same level as from this morning

[mik]

if it`s running plain water in it , i would not wait too long to put some proper coolant /corrosion inhibitors into it.

[webbiegareth]

It'll be done in the next few weeks... provided the rest of the car isn't totally bad (i.e. my other thread about the strange leak), then I'll buy a new copper-core radiator off ebay, have it fitted and get some real coolant in there

[rowan194]

Originally Posted by mik

if it`s running plain water in it , i would not wait too long to put some proper coolant /corrosion inhibitors into it.

Heed this warning!!! I had a slow leak that I never managed to pin down, just topped up every few months, and eventually just had demineralised water in there. I never looked into it since the leak was so slow, but never considered that demin water only could cause problems. A year later a welch plug sprung a leak because it corroded right through.

I wouldn't call welch plugs "easy" either as you have to remove the exhaust manifold (on that side) and there's very little room to get leverage to hammer the new ones in. The inlet manifold side would be more fiddly since you have to remove the injectors, throttle body, inlet manifold etc. And of course the one at the back is an engine out job.

Incidentally once I replaced the row of welch plugs and put the proper bright green stuff into the cooling system, it became quickly apparent there were other small leaks: at the water pump bypass, the thermostat housing, and one of the heater connections. You may find once you change to the proper "visible" coolant that you could also have other minor leaks.

[mik]

too true Rowan194 , aluminum does`nt like plain water, it corrodes quickly.

[Beer Baron]

Some people find certain things hard that others find easy and visa versa.

I find body work and listening to talk back radio hard.

[webbiegareth]

Okay guys, time for an update... the rad cap did fix the coolant usage issue, it no longer constantly used coolant... well, tap water in this case!

Took it to my mechanics for new pads/rotors and he complained a LOT that the radiator was totally stuffed (corroded) so the end result was a new radiator, new bottom hoses, new thermomstat and new coolant.

Much much better now...