Do I have the right coolant filler cap?140 or 100?

downcows · 11th May 2011, 19:09

Hello everyone,

I have a 1.8t ZT and just noticed that the filler cap for the coolant reservoir says 140. Isn't 140 for the diesel and the petrol should have 100 stamped on it?

Is there any practical or serious issue having the 140 cap if this is the case?

Thanks very much, Dave

Cymrudragon · 11th May 2011, 19:45

18/1.8t petrol, are 100 psi some are 140, it depends on the sn number the derv are all 140 psi. , the v6 petrol is the same as the 1.8....i believe rimmers will give you the SN...

T-Cut · 11th May 2011, 21:28

All models now use the '140' rated pressure cap. The 140 is the relief pressure in an obscure measure nobody's ever heard of. Anyway, the 140 equates to 1.5 bar or 22psi.
This means the coolant will blow the relief valve at 120-122C.

TC

rrobson · 11th May 2011, 22:03

black coolant bottle, 100kpa cap (usually grey). yellow/cream/whatever colour it is coolant bottle, 140kpa cap (always black)

140kpa = 20.3psi

T-Cut · 11th May 2011, 22:10

As I understand it, the original pressure caps have a single relief valve set to 100 kiloPascals (15psi), which explains the '100' stamped on them. However, during development, BMW were concerned about the overpressures developed during heat soak. This was especially seen in the K18 Turbo and in the diesel engine, which has a cast iron block and thus a large thermal inertia. To cope with this, they introduced the 2-stage cap. Here, there is a second relief valve within the cap body. This is isolated from the other by the two O-rings. This section has a small vent hole and senses pressure in the upper radiator hose by means of the small bore connection to the header tank neck. The earlier header tanks don't have the pipe and will not operate properly with the later cap. Some postings have referred to this small bore pipe as the overflow pipe. That's not correct, since any coolant discharged from the cap simply comes out around the thread.

The standard cap for all 75/ZT engines is now the one marked '140', which means it will cope with a heat soak overpressure of 140kPa or 21psi. This is provided the header tank is fitted with the small bore pipe from the head to the filler neck. Fitting this cap doesn't alter the normal running pressure of 100kPa or 15psi.

TC

rrobson · 11th May 2011, 22:27

basically, what that means is fit the cap stamped 140.

some interesting info tc

T-Cut · 11th May 2011, 23:05

Here's some more interesting data I put together on Pressure Caps.

If anything's not clear, just ask and I'll explain in detail.

TC

downcows · 12th May 2011, 07:09

Thanks very much for all the info guys, very informative.

Great forum, Cheers.

Dave

11th May 2011, 19:09	#1
downcows Regular poster MG ZT 1.8t Join Date: May 2009 Location: Walsall Posts: 62 Thanks: 0 Thanked 0 Times in 0 Posts	Do I have the right coolant filler cap?140 or 100? Hello everyone, I have a 1.8t ZT and just noticed that the filler cap for the coolant reservoir says 140. Isn't 140 for the diesel and the petrol should have 100 stamped on it? Is there any practical or serious issue having the 140 cap if this is the case? Thanks very much, Dave

11th May 2011, 22:03	#4
rrobson I really should get out more....... 75 tourer cdti, MG ZS 180, nissan terrano & 1.8t rover 25 Join Date: Feb 2010 Location: Pontefract Posts: 2,644 Thanks: 17 Thanked 295 Times in 218 Posts	black coolant bottle, 100kpa cap (usually grey). yellow/cream/whatever colour it is coolant bottle, 140kpa cap (always black) 140kpa = 20.3psi __________________ How to view a car - everything you need to help you inspect a used car VIS motor tester avalible to local members Injector removal tool and auto gearbox pressure tester now available Last edited by rrobson; 11th May 2011 at 22:06..

11th May 2011, 22:10	#5
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,753 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	As I understand it, the original pressure caps have a single relief valve set to 100 kiloPascals (15psi), which explains the '100' stamped on them. However, during development, BMW were concerned about the overpressures developed during heat soak. This was especially seen in the K18 Turbo and in the diesel engine, which has a cast iron block and thus a large thermal inertia. To cope with this, they introduced the 2-stage cap. Here, there is a second relief valve within the cap body. This is isolated from the other by the two O-rings. This section has a small vent hole and senses pressure in the upper radiator hose by means of the small bore connection to the header tank neck. The earlier header tanks don't have the pipe and will not operate properly with the later cap. Some postings have referred to this small bore pipe as the overflow pipe. That's not correct, since any coolant discharged from the cap simply comes out around the thread. The standard cap for all 75/ZT engines is now the one marked '140', which means it will cope with a heat soak overpressure of 140kPa or 21psi. This is provided the header tank is fitted with the small bore pipe from the head to the filler neck. Fitting this cap doesn't alter the normal running pressure of 100kPa or 15psi. TC Last edited by T-Cut; 11th May 2011 at 22:16..

11th May 2011, 22:27	#6
rrobson I really should get out more....... 75 tourer cdti, MG ZS 180, nissan terrano & 1.8t rover 25 Join Date: Feb 2010 Location: Pontefract Posts: 2,644 Thanks: 17 Thanked 295 Times in 218 Posts	basically, what that means is fit the cap stamped 140. some interesting info tc __________________ How to view a car - everything you need to help you inspect a used car VIS motor tester avalible to local members Injector removal tool and auto gearbox pressure tester now available

11th May 2011, 23:05	#7
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,753 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	Here's some more interesting data I put together on Pressure Caps. If anything's not clear, just ask and I'll explain in detail. TC Last edited by T-Cut; 12th May 2011 at 20:09.. Reason: Correction to Image

11th May 2011, 19:45	#2
Cymrudragon I really should get out more....... MGZTT2.5 V6 190+ SE 2002 Join Date: Oct 2009 Location: Gilfach-goch Posts: 2,201 Thanks: 0 Thanked 8 Times in 4 Posts	18/1.8t petrol, are 100 psi some are 140, it depends on the sn number the derv are all 140 psi. , the v6 petrol is the same as the 1.8....i believe rimmers will give you the SN...

11th May 2011, 21:28	#3
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,753 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	All models now use the '140' rated pressure cap. The 140 is the relief pressure in an obscure measure nobody's ever heard of. Anyway, the 140 equates to 1.5 bar or 22psi. This means the coolant will blow the relief valve at 120-122C. TC

12th May 2011, 07:09	#8
downcows Regular poster MG ZT 1.8t Join Date: May 2009 Location: Walsall Posts: 62 Thanks: 0 Thanked 0 Times in 0 Posts	Thanks very much for all the info guys, very informative. Great forum, Cheers. Dave