Best place to start looking for a coolant leak?

[Milowokie]

Picked up my 9-5 Aero this afternoon, and one the way home pinged the LOW COOLANT LEVEL, so topped it up.

Got home and left the car running whilst checking out the toys, and it came on again. Waited for it to cool down and topped the level up again.

So I expect to have either a big air lock, or losing some coolant somewhere.

Alas, it was chucking it down all day, so I can't find any traces of coolant on the drive or check where any drips may have come from, hopefully I can check properly tomorrow.

The last two times I've had unexpected coolant loss were both from corroded hose clips that let go, leaving the radiator bottom hose to come free (first on the way to Shell Oils Hairpin at Oulton Park in my V6 ALFA, and the other reversing onto my drive in my 9000 Carlsson).

Web checks seem to point to a heater by-pass valve in the 9-5s case though...

[sgould]

Heater by-pass valve is so common, that's the first place to look.  I doesn't leak all the time.  But a tickle underneath it usually finds a damp bit.

By-pass is between the engine and the rear bulkhead.  Often a Vauxhall dealer will be cheaper for a replacement as the same part is used on Vectras.

[phil-saab]

Agreed,  coolant by-pass is the culprit,  changed mine and all is well.

[Milowokie]

Where is it?

I've had a look from the n/s of the engine bay towards the back of the engine, front bulkhead area, but can't see anything that resembles a Top Hat.

Mine does have an LPG system fitted and there's a lot of extra gubbins near the injector rail and pipes coming into the engine bay to them.

Could it have been relocated, ie is in mounted on a decent fixed fitting, during the installation?

Still chucking it down, so can't tell if anything/where anything is dripping from.

May pop it to my indie when the paperwork's sorted, it'll be having a coolant/oil/plugs and filter change anyway.

Still I'd like to be able to identify if it is or isn't the problem (see post about bottom rad pipe clips), in case the problem reappears in the future.....it seems it more common than I would have thought, compared to my Carly.

[phoenix]

Not all models have the bypass valve fitted- mine (MY03) doesn't. I think it was just earlier ones.

[Milowokie]

Ah, the thot plickens.

Mine's a 53 plate, but 04MY

Still not nice outside, any under bonnet activity will have to wait for fair heavens.

[sgould]

Ah! You have the modified engine as well.

My 2006/7 car has no heater by-pass valve.

[Milowokie]

Yep, and the quarter bumper rubbing strips, and nicer front spoiler/bumper.

As with any "new" second-hand car, there'll be a few issues, hopefully nothing serious or expensive.

Other than the unexpected coolant loss, everything else on the car works fine, and the trip back hope was very smooth and relaxing.

Two unexpected gifts, about 18p in cooper in the ashtray, and a Take That CD in the player, should I send that back to the seller?

In my ALFA I found a lot of golf tees and a loaded shotgun shell (taken to the local Police station on discovery).

[cattytown]

On my '02 3.0TiD the Bypass was below the main big bulkhead connector.

I would also have a look for moisture neat the coolant header tank.

Paul.

[Milowokie]

Nice day today, so fired up the 9-5.

Had topped up the coolant on Wednesday (2nd time), and it was full.


Opened up the bonnet this morning and still full.

So fired it up.

With the heater set to full, I watched with baited breath the Coolant Temp gauge rise to half-way, whilst getting gently warmed.....

Coolant still full, no fans on yet, gets past halfway, and the fans come on (they're very quiet by the way).

Coolant still full, but a few bubbles from the small hose at the front.

Switch the heater to cool (ECON), and wait for the fans again, more bubbling in the expansion tank, which has now gone down to the Cold measure.

Car's been on nearly an hour and no serious sign of coolant loss, there's a small puddle (about a tablespoon's worth) which was dripping from a pipe low down behind the engine. A/C Evap spill?

Still have been unable to locate the usual culprit of the heater by-pass valve (but I'm not sure if MY2004 has one).

I'll check again once it's cooled down and see what the level is like.

So it's gone from (over) full when cold to the COLD marking when hot.

[phoenix]

Shouldn't really be any bubbling in the expansion tank; once the system has self bled after initial fill, that's it. How big are the bubbles?

[Milowokie]

Very small, as if air was working it's way to the top of the expansion tank. Not like something boiling in a pan!

EDIT: Just returned home from work and the, now cool, coolant has remained around the COLD marking.

I'll risk a run to work in in tomorrow, new insurance kicks in at one minute past midnight and see how it goes.

Yes, I'll have the emergency 5 litres of water with me.....just in case.

[phoenix]

I do hope I'm wrong but little bubbles sound worryingly like head gasket loss 

[Milowokie]

Little bubbles coming from the small pipe leading into/out of the expansion tank, not all the time though.

Not a lot of bubble action once the level has dropped below the level of this pipe.

[Milowokie]

Got back from my indie, car's booked in for a service on Wednesday. Looked for the leak and found it straight away. A pipe has split where the clip been over tightened. No sign of a leak from there when it'd been on idle last week, so must only leak at running pressure.

Replace the hose and all should be well.