VX Series 2 auto - occasional overheating probs, may be air con only issue

[ShannonN]

Hi all
My VX II Berlina has 150,000 on the clock and was ex company car with full Holden service history. Lately is has overheated due to water loss with no apparent reason.
To explain, had the car 15 mth never ever boiled before. As a result I never had to check water levels less than weekly, car boiled a few weeks ago after driving 10 klms, pulled over, safely opened bonnet no leakage from any visible hose ( steam, pinhole water streams, under car loss etc. Waited appropriate time to cool, (car was NOT really hot as radiator cap was warm not hot radiator was hot but not the scalding hot you'd expect, thematic fan was running beautifully ( ignition left on for this to happen. slowly refilled 3 litres? run car to pump through, , topped up, drove home safely no further boiling. At home, while car at normal operating temp and running, looked under bonnet/car for leaks, none! did this for 15 with car running in park.

Turned car off, for next 2 hrs checked every 10 mins for under car/engine bay water leaks, none apparent at all.

Checked coolent every few days no appreciable loss. Last week hot weather called for lots of air con use, yesterday boiled, it appears that ONLY after using air con, it dumps water under car (more than most air cons do.) emptying radiator levels below safe normal causing it to not hve enough to cool properly, not knowing this was the case at the time, I never did a check on coolant level before driving off.

Since that instance, the refilling etc etc. I now check daily. Filled radiator full, overflow tank to level, Tested today drove 200 klms using NO aircon, absolutely no water loss. Here's the prob, while I will get it looked at by mechanic/air con specialist. Can anyone explain why this is happening?

Things I have checked.
New radiator cap, All radiator hoses,clamps etc look new, no swelling, bumps no leaks when hot or "pressurized"
Top Radiator hose gets hot when car up to temp, Bottom hose warm, not as hot as top hose. indicates flow through radiator/thermostat functioning.
No oil or rainbow film in water, NO milky sludge under oil cap. Plugs all nice even grey colour. No missing or spluttering on acceleration. Idles great. water temp gauge sits at between 1/4 & 1/2 appears normal for this car.

NO water leaks ever inside car, suggests heater hoses, radiator etc. ok car heats very well and cools well using heater/fan/aircon system
No apparent leakage at water pump, watching radiator level when cold starting level drops slightly as car runs and warms, suggests thermostat ok and pump works.

Unless there is some one way valve for air con overflow etc that is stuck open I haven't a clue . and you can imagine I don't want to take it to a dealer and get charged 75 to drive it in, 75 to put on hoist 75 to raise on hoist 75 for mechanic to look under car, 75 for mechanic to wash hands with soap etc if its a known simple fault (E.G. the XX hose can rub and only dumps water when air con pressurized etc.)

Thanks for listening, you been a great audience
Shannon

[umair]

You have a pinhole in your radiator tank. When you turn on the ac and radiator gets double hot the pinhole opens and all the water leaks out. Then it magically closes by itself and there are no leaks and nothing. I had same problem. To confirm it park the car, fill water in radiator and start the car and let it reach normal temperature and then turn ac on and leave it. After 30 to 40 minutes the pinhole will open and the water will spray out. Locate the side the pinhole is in and change that side radiator plastic tank. Plasic tanks are cheap, over here they are 10 dollar. Also clean the radiator with a wire when you open it up to change the tank. Also please note that when the water will spray out it will suck in air and the car will overheat. When you locate the pinhole turn the car off. Pinholes are small crack that happen in radiator seams and weak points due to cooling inefficiency (the car cooling system becomes weak as it gets older). Most people change renew there cooling system every 4 years. Do not turn the ac on untill you get it fixed.

[ShannonN]

Hey thanks for that advice, it makes perfect sense. I will test as you ask and report back .
Cheers Shannon

[ShannonN]

Solved:

Following Umair's advice I ran the car with air on etc for some time then looked for pinhole type leaks. Radiator was fine, was heater tap unit, one of the plastic "nipples" had cracked and was leaking when pressurized, only when parked in sunlight and hot could it be seen, unit has been replaced and system refilled bled and tested fine.

A flush and refill etc was gunna happen, however my car has those shitty spring clamp on radiator hoses turned in the most awkward place to grip and undo with multi grips etc. so next week I'll borrow ramps so i can get under and see what I'm doing, then my demineralised water, expensive additives etc. won't be wasted LOL. mind you a MAF sensor clean with proper electrical spray did wonders for idle and smooth running. Feel confident to do some distance driving again now.
Thanks umair & forum for lots of good tip and hints.

[umair]

My advice get the radiator cleaned every year. Thats what I do and I have had no problems in my car for five years.

[The_Doctor]

Sounds like you have a problem, I don't believe your air conditioner is even connected to your cooling system, your heaters may be though.check for water loss thru heater hoses and if none get a flush from a radiator place

[The_Doctor]

Oh and heater hoses run all way into heater, any wet carpet?

[The_Doctor]

Oh, I had a VX for 8 years and never had it cleaned, but I used coolant and that won't make it dirty.