Commodore losing coolant.

[RANDY]

Anyone have any clues?
Over the course of 3 weeks or so, I lose the entire contents of my overflow bottle.

So far:
pressure test shows no pressure loss.
no obvious leaks in engine bay.
water pump seems to be fine.
no leaking in cabin.

I'm lost! =-]

Thanks guys and girls.

-Steve

[Sturmovik]

What model commodore and what engine would be helpful

[RANDY]

hehe.. i meant to include that.. thanks!

VP V8 series 2 (waterpump at the front)

[gtst4]

The cap is OK?

Has the cooling system been recently drained and refilled? Could be an air-lock being gradually removed.

[RANDY]

gtst4 (or is it gts4???) =-]

yeah.. i put a brand new radiator in it (after problem) and my mechanic put a new genuine cap on it (correctly rated).

air lock? where abouts is that?

thanks mate =-]

[guidos]

do a compression check, cracked heads or blown gaskets can cause that sort of problem. did with my VL.

[Lewd Lude]

i was going to say gasket...do a compression test...

[RANDY]

i rebuilt the motor (minor rebuild) less than 6 months ago, and put new genuine seals and gaskets on. my mechanic said that he'd checked the compression. do you have to check every chamber?

thanks again. =-]

[Swill]

Sounds like a cracked head. Try doing the compression test when the motors hot as some times the cracks only open up when the motor is at running temp. With any luck its a head gasket, and yes test every cylinder......

[RANDY]

YRALLY: will do...
When i rebuilt the motor, I had the heads ported, polished, and milled. (milling was just flattening, not increasing compression). The heads came back spotless, and looked great! The gaskets are all held in place by the heads themselves, so I can't imagine that it slipped.

But if the gasket is cracked somewhere, it'll show up on the compression test eh? =-]

Cheers.. will do that. =-]
-Steve

[wol]

It sounds like it was definately an air lock. When the new radiator went in with the new coolant, you should run the engine unil it reaches operating temperature (ie thermostat has opened). You will notice the coolant level in the overflow tank go down as air which was previously trapped, is released back into the overflow tank. I hope this makes sense. Its nothing to worry about, just top it up to the maximum level in the overflow tank and you,re done.

[Sxer]

If it isn't an air lock - you could try looking for white smoke or water in the oil to confirm a gasket problem - but then again - you probably already knew this...

[RANDY]

wol: I've topped it up a few times now. It's a reoccuring problem, unfortunately. =-[

Sxer: Oil is nice. No murky white stuff to be seen. Car blows next to no smoke (unless under full load), even then it seems fine.

But that raises a good point... No funky white stuff means no gasket leak? Means no need for compression test on each cyl?

Thanks guys. =-]
-Steve

[sed8]

if it still doing check the overflow hose into the bottle as i can't remember the type of setup the vp runs if its the same as the vn s1 and hold pressure in the overflow bottle then its unforntunatly something worth investigating but if the over flow bottle doesn't hold pressure and has the radiator overflow hose and the overflow bottle overflow hose on it usualyy black which also is the filler cap try swapping the hoses around so the one that runs to the radiater is on the longer tube and and the overflow for the bottle is on the short hose. if its wrong as soon as the engine creates pressure then the radiator overflows if the hose from the radiator is the short one in the bottle it will but everything out of the bottle thru the long as it the only way out

[RANDY]

Thanks. =-]
The VP and VN series 2 have pressure caps on the radiator, and no pressure is kept in the overflow bottle. I looked into it, and nothing is leaking there. Basically the radiator isnt spitting any to the overflow bottle, and the bottle isn't dripping any out of the second pipe.

-Steve

[tez]

Have you taken the car for a cain around the block (up to operating temp) and then had a look for any leaks in pipes etc? I had the same problem once, but it was on a old Magna of mine but it had a pin hole size leak in one of the hoses and would only come out when up to operating temp. Had me buggered for ages. And it wasnt as obvious because the water would spray out, but because of the heat in the engine bay, it would all dry up quickly, making it hard to detect.

[RANDY]

Hmm.. .will try that. My mechanic did a pressure test (quite high pressure, I don't remember exactly how high it was in PSI though), and it maintained pressure perfectly.

Maybe the heat expands a theoretical hole in the pipe? I'll definately check that one. ta =-]

[Bob Saget]

I've got the same problem atm with my VN SS the thing doesn't go above the first notch on the temp guage but if i drive 2 mins down to the servo and stop it empty's out the overflow bottle(comes out of the overflow like it's overheating but it's not). I've down a full compression test and found nothing. I ended up putting a bolt in the end of the overflow bottle hose. Let me know if you find the problem its got me stumped. It could be the little cap thingy on the overflow bottle but i haven't had the chance to change mine.

[RANDY]

FaTs: mine goes to normal operating temp properly, and sits there just fine. On a hot day, it goes right up to half. If i stick the airconditioning on, it'll add half the guage to wherever it is!

That's a different story anyways, yours sounds like the pressure-cap is incorrect. From what I've been hearing, if the pressure sensitivity of your radiator cap is too low, it'll let fluid out at a low temp/pressure, into your overflow bottle. Then the reason that your temp doesn't come up properly is possibly something to do with your thermostat. If it's stuck open, you'll have constant flow all the time. Including startup.
I'd check them out if I were you. =-]

[Bob Saget]

Already done that randy, i've put 2 new 16psi caps on and still no difference. Doesn't really matter because i've cracked a piston in this motor now and it's getting binned and something decent like a 1UZ-FE is going in

[Stix Zadinia]

is it the correct cap for a reseviour? theres two different cap designs, one for a resevior, and one for without....

although, this seems like a pretty silly oversight, it's just something noone has mentioned (so don't shoot me for looking stupid)

[VH_SL/E]

If there is no leak from any of the hoses, or the cap. There could be a slight leak through one of the welsh plugs. One of the welsh plugs could be corroded and has a pinhole leak.

Take it to your nearest cooling places and get them to pressure test it. They do it while you are there and only costs $20 or so. They will tell you if its holding pressure.

If its not in the oil it MUST be leaking out somehow. Like someone else said, start car with the cap off and wait till the thermostat opens. It should suck some water down. Fill it when this happens. Then your cooling system is full.

It has to go somewhere.

[RANDY]

yer, thing is: pressure test has been done, and is fine. perfect infact. oil doesnt have mirky white stuff that you get when water and oil mix, and radiator has been refilled along with the overflow bottle.

It must be (i hope anyway) an external leak, just a matter of heating it up and having a look. =-]

thanks....

-Steve

[gtst4]

Is the pressure test done hot or cold?

I once had a leak in my Z's cooling. At idle, it didn't show, but with a few revs, it caused the coolant to spray through a pinhole on the underside of the thermostat hose connection.

Try giving it a few revs while watching for the spray under the bonnet.

[RANDY]

motor was at operating temp, the test was done 5 minutes after i drove in the workshop.

but yer... i'll get it toasty hot next time. =-]

[VH_SL/E]

It has to go somewhere. Either into sump or out of hose, radiator, welsch plug, or heater box. But if its only the overflow in 3 weeks, thats not too bad. Its not good, but unless its running hot or you're worried....forget about it. Just top it up once a week.

[RANDY]

heheh.. thats what ive been doing for the last 2 years! =-]
It's only when I came across this guru mechanic (Carisma in Brookvale, northern beaches) that I started to be concerned. He is VERY podantic about detail. Unless everything is 100%, he doesn't quit. He actually called me a month after my service and asked me to bring it in again for him to check. Thats when he did the pressure test again and other misc checks. (didnt charge for)

He wants me to keep an eye on it, and also measure my fuel economy?? weird, but he wants me to check it nonetheless. =-]