Coolant Loss through Filler Cap? - Page 2

BigJacko · 12th November 2013, 14:56

I agree, Kaiser - if there is significant pressure after 24 hours cooling-down, then that implies combustion-gases are in the coolant, and they've not found their way back out via the same way they came in (ie the engine).

However, I would also expect to see some 'mayonnaise' in the radiator cap - though this isn't a given, if there's no oil getting in to the coolant - but then again, a HGF where only exhaust gas but no oil is getting past? How realistic is that? (I have no direct experience with this on my R75 and I hope never to, so it's a genuine question! My gut tells me that oil and gas together is a far more likely outcome, rather than one or the other.)

Back to first principles, though - and I call 'overfill' as the first item to rule out. The OP said that upon opening the rad cap, some pressure and some coolant came out too. To my mind, that would indicate *major* pressure if the expansion tank had been filled to the correct level prior to all this. To be lifting the water-level to beyond the neck of the tank 24 hours later, seems, well..., improbable. I would expect the OP to be reporting all manner of gurgling and bubbles at the same time too, yet he doesn't.

Perhaps the OP can elaborate - where was the coolant filled to, in terms of level? Did you cover the fins inside the expansion tank? Have you seen the MIN/MAX markers inside the expansion tank (directly below the filler opening). Have you seen the second set of MIN/MAX marks on the nearside wall of the expansion tank exterior? You would be amazed how many garages don't have a clue about how to fill an R75 coolant tank.

If you don't know any of the above, just tell us what level the coolant shows, after you've opened the cap (after cooling down). If it's still way, way over the MIN/MAX marks, I'd get that straightened out before plumping for HGF as the cause. Conversely, if there really was a HGF, and thus some pressure had been introduced, I would expect (after cooling-down) that the coolant levels would return to (true) normal, possibly even lower than normal, once the gas had vented off after you opened the cap.

If the tank has been filled to brimming, there's not going to be enough room for normal operation and expansion - remember the water-pump at high revs is enough to raise the water level by an inch or two on its own, hence the seemingly low min/max level marker. There is also no overflow pipe on this system; it's a sealed, pressurised arrangement. You'd be hard-pushed to remove a rad-cap on an overfilled system without spilling some coolant, because the end of the cap will be well and truly immersed already (so some will drip out of it as you remove it), plus any 'normal' pressurisation will doubtless cause a bit of a spill-over, simply because the level was overly high and nearer the neck to begin with.

Do let us know the score - it may be a game-changer.

DMGRS · 12th November 2013, 15:28

It's worthy of note I had an aftermarket coolant cap on my old 75 which leaked under pressure - an OEM item solved it.
I've just started stocking them:
http://www.dmgrs.co.uk/search?q=rover+75+coolant+cap

kaiser · 12th November 2013, 15:28

You will only expect mayonnaise if water is getting into the oil. That will most likely happen further down the road, if not now.

However, it is entirely possible to have no other symptoms than over pressure, and if you measure, exhaust in the coolant, which you might be able to smell, but not see. That will happen if only combustion gases get into the water .

If water gets into the oil, mayonnaise!

BigJacko · 12th November 2013, 15:42

Quote:

Originally Posted by DMGRS

It's worthy of note I had an aftermarket coolant cap on my old 75 which leaked under pressure - an OEM item solved it.
I've just started stocking them:
http://www.dmgrs.co.uk/search?q=rover+75+coolant+cap

Neat. You've just sold one, too, Mat (Order #1542). I was just about to purchase an aftermarket one from Ebay for a little less, but I'd rather have the real McCoy, and from a fellow forum member. And look - you now have enough money to turn your forum-name red! (hint, hint, LOL).

DMGRS · 12th November 2013, 15:45

Quote:

Originally Posted by BigJacko

Neat. You've just sold one, too, Mat (Order #1542). I was just about to purchase an aftermarket one from Ebay for a little less, but I'd rather have the real McCoy, and from a fellow forum member. And look - you now have enough money to turn your forum-name red! (hint, hint, LOL).

I'm one above red - I'm bold blue!

Thank you for the order - I was rather shocked when I got my pricing for them sorted out. I'm only happy to supply the OEM items, as I've had a leaky non-OEM item before as mentioned.

BigJacko · 12th November 2013, 15:52

Quote:

Originally Posted by DMGRS

I'm one above red - I'm bold blue!

Thank you for the order - I was rather shocked when I got my pricing for them sorted out. I'm only happy to supply the OEM items, as I've had a leaky non-OEM item before as mentioned.

Whoops - sorry Mat - I had you down as just a 'blue' guest... I didn't realise there was a bold-blue too. I only knew about the greens and the reds. I'm guessing bold-blue is trader?

Things move so fast round here, I think I'm standing still... LOL.

Anyway - back to the main programme, my apologies for the interruption!

I'm with MangoMan - I do hope the OP resurfaces. I hate it when we get a 'hit-and-run' help request with no sign of a followup. But maybe he's still at work, or mopping up coolant off his driveway or summat!

rich17865 · 12th November 2013, 16:03

Don't forget there is a seller on eBay who offers the viton rings for the coolant cap too.

And there are us Purple members as well as the Blue, Red, Bold Blue and Green's

stocktake · 12th November 2013, 16:12

Quote:

Originally Posted by DMGRS

I'm one above red - I'm bold blue!

Err, since when is this correct

Quote:

Originally Posted by kaiser

The situation is simple. He says he has over pressure after 24 hours. That is different from any other coolant pressure in the engine, which is ONLY temperature dependent.
That means if you cool the engine to ambient, there will be a pressure inside the system, which only relates to the ambient temperature, give and take a small amount of pressure, caused by a bit of "stickiness" in the equalization valve in the cap. You can thus expect a small sigh or suck when you open, but not more than that.

If there is a significant amount of pressure residual in the system, it is from the cylinders and it will be caused by a fault.

If there is no excessive pressure, then that is another case, but I am basing my diagnoses on the accuracy of the report originally stated.

If that is accurate, there IS only one explanation.

Unfortunately this is correct. I 100% agree, think about it. when the engine is cold you inspect the water level screw the cap on and off you go. It doesn't matter what happens in between then and the next time the engine is cold and you take the cap off to look. If there is more in there than there was before by way of fluid or pressure, it has to have come from somewhere..... Sorry

James.uk · 12th November 2013, 16:20

>>>Open your bonnet after running your engine and turning it off and CAREFULLY (IT CAN BURN YOU) unscrew the cap<<<

DO NOT TRY THE ABOVE if the engine is up to norm temp....

When the engine is up to running temp the coolant temp is ABOVE boiling point. Undoing the cap lowers the pressure in the system allowing the fluid inside to boil, and it then comes out of the filler cap like a volcano!! It will hit the raised bonnet and bounce forward all over you....... I saw this happen, the guy was in hosp for a couple of days, and still has scars on his face.............

...

DMGRS · 12th November 2013, 16:24

Quote:

Originally Posted by stocktake

Err, since when is this correct

A tongue in cheek comment, hence the '

'

Blue is indeed Trader - there's a fair few of us kicking about now.

12th November 2013, 14:56	#11
BigJacko Avid contributor Rover 75 Tourer 2.0 V6 Club (2002) Join Date: Dec 2007 Location: Bath Posts: 236 Thanks: 47 Thanked 16 Times in 12 Posts	I agree, Kaiser - if there is significant pressure after 24 hours cooling-down, then that implies combustion-gases are in the coolant, and they've not found their way back out via the same way they came in (ie the engine). However, I would also expect to see some 'mayonnaise' in the radiator cap - though this isn't a given, if there's no oil getting in to the coolant - but then again, a HGF where only exhaust gas but no oil is getting past? How realistic is that? (I have no direct experience with this on my R75 and I hope never to, so it's a genuine question! My gut tells me that oil and gas together is a far more likely outcome, rather than one or the other.) Back to first principles, though - and I call 'overfill' as the first item to rule out. The OP said that upon opening the rad cap, some pressure and some coolant came out too. To my mind, that would indicate *major* pressure if the expansion tank had been filled to the correct level prior to all this. To be lifting the water-level to beyond the neck of the tank 24 hours later, seems, well..., improbable. I would expect the OP to be reporting all manner of gurgling and bubbles at the same time too, yet he doesn't. Perhaps the OP can elaborate - where was the coolant filled to, in terms of level? Did you cover the fins inside the expansion tank? Have you seen the MIN/MAX markers inside the expansion tank (directly below the filler opening). Have you seen the second set of MIN/MAX marks on the nearside wall of the expansion tank exterior? You would be amazed how many garages don't have a clue about how to fill an R75 coolant tank. If you don't know any of the above, just tell us what level the coolant shows, after you've opened the cap (after cooling down). If it's still way, way over the MIN/MAX marks, I'd get that straightened out before plumping for HGF as the cause. Conversely, if there really was a HGF, and thus some pressure had been introduced, I would expect (after cooling-down) that the coolant levels would return to (true) normal, possibly even lower than normal, once the gas had vented off after you opened the cap. If the tank has been filled to brimming, there's not going to be enough room for normal operation and expansion - remember the water-pump at high revs is enough to raise the water level by an inch or two on its own, hence the seemingly low min/max level marker. There is also no overflow pipe on this system; it's a sealed, pressurised arrangement. You'd be hard-pushed to remove a rad-cap on an overfilled system without spilling some coolant, because the end of the cap will be well and truly immersed already (so some will drip out of it as you remove it), plus any 'normal' pressurisation will doubtless cause a bit of a spill-over, simply because the level was overly high and nearer the neck to begin with. Do let us know the score - it may be a game-changer. __________________ [SIGPIC][/SIGPIC]

12th November 2013, 15:28	#12
DMGRS Discount MG Rover Spares Rover 75 CDTi, 2x MG ZS180 Join Date: Jun 2011 Location: Hythe, Southampton Posts: 11,321 Thanks: 456 Thanked 3,377 Times in 2,027 Posts	It's worthy of note I had an aftermarket coolant cap on my old 75 which leaked under pressure - an OEM item solved it. I've just started stocking them: http://www.dmgrs.co.uk/search?q=rover+75+coolant+cap __________________ Your trusted MG Rover specialist! Tel: 02380 001133 / Email: [email protected] We now have a 'chat' function on our site for even quicker replies. Give it a try! Remember - discount code FORUM5 for 5% off

12th November 2013, 15:28	#13
kaiser This is my second home 75 Tourer 2.5 Auto, 1.8T, 75V8ZT Join Date: Jun 2007 Location: Johannesburg ZA Posts: 6,200 Thanks: 1 Thanked 859 Times in 613 Posts	You will only expect mayonnaise if water is getting into the oil. That will most likely happen further down the road, if not now. However, it is entirely possible to have no other symptoms than over pressure, and if you measure, exhaust in the coolant, which you might be able to smell, but not see. That will happen if only combustion gases get into the water . If water gets into the oil, mayonnaise!

12th November 2013, 16:03	#17
rich17865 This is my second home Transit Connect Join Date: Feb 2011 Location: Crewe Posts: 9,532 Thanks: 868 Thanked 1,619 Times in 1,095 Posts	Don't forget there is a seller on eBay who offers the viton rings for the coolant cap too. And there are us Purple members as well as the Blue, Red, Bold Blue and Green's

12th November 2013, 16:20	#19
James.uk Passed Away 2002 Pale Blue. Rover 75 CDTi Connoisseur auto. 170K miles Join Date: Dec 2008 Location: Near the M67. Posts: 14,509 Thanks: 199 Thanked 585 Times in 397 Posts	>>>Open your bonnet after running your engine and turning it off and CAREFULLY (IT CAN BURN YOU) unscrew the cap<<< DO NOT TRY THE ABOVE if the engine is up to norm temp.... When the engine is up to running temp the coolant temp is ABOVE boiling point. Undoing the cap lowers the pressure in the system allowing the fluid inside to boil, and it then comes out of the filler cap like a volcano!! It will hit the raised bonnet and bounce forward all over you....... I saw this happen, the guy was in hosp for a couple of days, and still has scars on his face............. ...