Coolant Loss through Filler Cap?

M123 · 12th November 2013, 12:28

I am getting regular coolant loss through I think the filler cap. I have just replaced the cap with a brand new one, but still loosing coolant. After leaving the car to cool for 24hrs I open the cap and it seems pressurised with air and a little coolant being expelled. Anyone know what's going on here? Is it something like a head gasket leak?

Greeners · 12th November 2013, 12:40

Make sure you don't over fill it....check out the picture in the link below

stevestrat · 12th November 2013, 12:47

The max level is lower than you think, visible at the bottom of the tank, see pic below courtesy of Arctic.

wullie480 · 12th November 2013, 13:09

My wife's zt suffered this recently and what I found was the cap wasn't far enough on although it felt tight.
Might I suggest a smear of Vaseline on the o rings & on the inside of the reservoir and screw it on and off a few times.

Worked for me.

BrainKing · 12th November 2013, 13:27

Its not overheating is it? Open your bonnet after running your engine and turning it off and CAREFULLY (IT CAN BURN YOU) unscrew the cap. Is it full with pressure? Is it bubbling away?

kaiser · 12th November 2013, 13:31

If your cooling system is pressurized after standing for 24 hours (and I am talking about pressure, not just a little pfft!) then that can only come from one source, and that is exhaust gases from the cylinders.
That would indicate either a failure of the head gasket or a crack.

There might only be passage for gas at the moment, but it will eventually develop into something more.

I hope I am wrong, but I think not.!

And it is true that the level in the expansion box is lower than most think. However if you overfill, that will just be spat out. It will not lead to overpressure.

BrainKing · 12th November 2013, 13:38

I highly doubt its the head gasket. Remember hes got a v6 2.5. Not very common to fail and overheat the engine. Usually the much older series or the ZS. There could be an air lock or a leak in the cooling system pipes and so its steaming up in the expansion tank as it passes through the engine because its not being cooled down, and because its steaming up in the expansion tank, its creating pressure, and the cap is designed to lift and release coolant under too much pressure.

kaiser · 12th November 2013, 13:53

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.

ashbash2403 · 16th February 2014, 05:17

Terry at tsautos in Stourbridge will diagnose it and very reasonable rates for the required work, all done properly ! Think the link to him ha already been added.

If not google tsautos Stourbridge.

Ash

12th November 2013, 12:28	#1
M123 Newbie 2006 Rover 75 Connoisseur SE Saloon 2.5 V6 Join Date: Nov 2011 Location: Birmingham Posts: 27 Thanks: 25 Thanked 0 Times in 0 Posts	Coolant Loss through Filler Cap? I am getting regular coolant loss through I think the filler cap. I have just replaced the cap with a brand new one, but still loosing coolant. After leaving the car to cool for 24hrs I open the cap and it seems pressurised with air and a little coolant being expelled. Anyone know what's going on here? Is it something like a head gasket leak?

12th November 2013, 12:40	#2
Greeners Moderator MG-ZTT Join Date: Mar 2007 Location: Ware, Herts Posts: 19,798 Thanks: 161 Thanked 1,249 Times in 1,036 Posts	Make sure you don't over fill it....check out the picture in the link below __________________ *David* Impecunity is the mother of ingenuity Useful how to's for common problems Car Of The Month Jan 2014 [SatNav Power Down] [Coolant Level] [SatNav Repair] [Diesel Non Starting] [Paint Codes] [Rear Light Seals] [Reversing Light Switch] [Bleeding Brakes][Sunroof Drain] [Early ZT's][Instrument Pack Diagnostics][ATC Diagnostics]

12th November 2013, 13:09	#4
wullie480 This is my second home 1 Join Date: Dec 2010 Location: Banned Posts: 5,196 Thanks: 528 Thanked 1,022 Times in 786 Posts	My wife's zt suffered this recently and what I found was the cap wasn't far enough on although it felt tight. Might I suggest a smear of Vaseline on the o rings & on the inside of the reservoir and screw it on and off a few times. Worked for me. __________________ [SIGPIC][/SIGPIC]

16th February 2014, 05:17	#9
ashbash2403 Loves to post MG ZT 1.8T 160 Xpower Grey Join Date: Jul 2010 Location: Aldridge Posts: 355 Thanks: 8 Thanked 15 Times in 15 Posts	Terry at tsautos in Stourbridge will diagnose it and very reasonable rates for the required work, all done properly ! Think the link to him ha already been added. If not google tsautos Stourbridge. Ash __________________ You don't need to own a sheep to know what not to put in it !

12th November 2013, 13:27	#5
BrainKing Banned MG ZT+ 2003, 2.5 V6, 160bhp Join Date: Oct 2013 Location: Beccles Posts: 229 Thanks: 26 Thanked 6 Times in 6 Posts	Its not overheating is it? Open your bonnet after running your engine and turning it off and CAREFULLY (IT CAN BURN YOU) unscrew the cap. Is it full with pressure? Is it bubbling away?

12th November 2013, 13:31	#6
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	If your cooling system is pressurized after standing for 24 hours (and I am talking about pressure, not just a little pfft!) then that can only come from one source, and that is exhaust gases from the cylinders. That would indicate either a failure of the head gasket or a crack. There might only be passage for gas at the moment, but it will eventually develop into something more. I hope I am wrong, but I think not.! And it is true that the level in the expansion box is lower than most think. However if you overfill, that will just be spat out. It will not lead to overpressure.

12th November 2013, 13:38	#7
BrainKing Banned MG ZT+ 2003, 2.5 V6, 160bhp Join Date: Oct 2013 Location: Beccles Posts: 229 Thanks: 26 Thanked 6 Times in 6 Posts	I highly doubt its the head gasket. Remember hes got a v6 2.5. Not very common to fail and overheat the engine. Usually the much older series or the ZS. There could be an air lock or a leak in the cooling system pipes and so its steaming up in the expansion tank as it passes through the engine because its not being cooled down, and because its steaming up in the expansion tank, its creating pressure, and the cap is designed to lift and release coolant under too much pressure.

12th November 2013, 13:53	#8
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	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.