Annoying water/coolant loss

pieterm · 29th March 2022, 06:25

I have a 2003 Rover 75 2.5 V6. The engine has been rebuilt professionaly, new head gasket, water pump, etc. But it is losing a small amount of water each day. Coolant has been added to the correct marks on the expansion tank. After running the engine to reach operating temperature plus 10 minutes or so, then letting it cool overnight, checking the coolant level will show it has lost around a quarter of a cup of coolant ... sometimes a little more. This adds up over a week or so, of course. No leaks appear apparant anyware and even removing the 'protector' under the engine shows no coolant on the floor. Obviously there must be a leak somewhere but goodness knows where. Any help would be appreciated. Thanks

SD1too · 29th March 2022, 07:11

Hello Pieter,

Check that the special KV6 refilling and bleeding procedure was carried out by the book.

Simon

Bob Walker · 29th March 2022, 07:18

Hi Pieter
Have you replaced the coolant pipe under the radiator with a stainless steel one? Another cause could be the coolant cap! They do deteriorate!
Bob

SD1too · 29th March 2022, 08:38

Quote:

Originally Posted by Bob Walker

Another cause could be the coolant cap! They do deteriorate!

But it may only need a pair of new 'O' rings. These can allow coolant to escape without leaving much evidence.

Simon

roverbarmy · 29th March 2022, 11:29

When you say "correct mark/s", are you just filling to the "MAX" mark, which is right at the bottom of the visible section of the header tank (You can actually see the word "MAX" printed on it). Filling any higher will just pressurize the header tank and the excess coolant will dribble out of the pressure vent.

pieterm · 29th March 2022, 21:56

Quote:

Originally Posted by SD1too

Hello Pieter,

Check that the special KV6 refilling and bleeding procedure was carried out by the book.

Simon

Yes, have followed the procedure to the letter, Simon

pieterm · 29th March 2022, 21:58

Quote:

Originally Posted by Bob Walker

Hi Pieter
Have you replaced the coolant pipe under the radiator with a stainless steel one? Another cause could be the coolant cap! They do deteriorate!
Bob

Coolant pipe under the radiator? That's one I haven't heard, Bob. As for the coolant cap, I have three new ones, all different brands - just to be certain LOL

pieterm · 29th March 2022, 22:02

Quote:

Originally Posted by SD1too

But it may only need a pair of new 'O' rings. These can allow coolant to escape without leaving much evidence.

Simon

Have tried three different caps, Simon - all different brands - just to be sure LOL. The cap feels tight and O rings are new, of course. I have noticed very slight ridges in the throat of the expansion tank but they are hardly noticeable. I'm thinking maybe to try slightly thicker O rings.

pieterm · 29th March 2022, 22:04

Quote:

Originally Posted by roverbarmy

When you say "correct mark/s", are you just filling to the "MAX" mark, which is right at the bottom of the visible section of the header tank (You can actually see the word "MAX" printed on it). Filling any higher will just pressurize the header tank and the excess coolant will dribble out of the pressure vent.

Yep, have filled to the MAX mark at the bottom of the header tank.

pieterm · 29th March 2022, 22:12

Thank you everyone for your helpful replies. This has to be the most annoying thing yet LOL. I check the coolant each morning and note it has dropped from the MAX mark. I top it up only to find the same thing the next morning. If I leave it a few days, it will drop from the MAX to the MIN marks. The weird thing is some mornings it will drop from the MAX to well below the MIN mark! I have pressure tested the system and it holds the pressure even after an hour. This one has really got me beat.

29th March 2022, 06:25	#1
pieterm Regular poster Rover 75 Connoisseur SE Join Date: Mar 2018 Location: Point Cook, Australia Posts: 83 Thanks: 69 Thanked 8 Times in 6 Posts	Annoying water/coolant loss I have a 2003 Rover 75 2.5 V6. The engine has been rebuilt professionaly, new head gasket, water pump, etc. But it is losing a small amount of water each day. Coolant has been added to the correct marks on the expansion tank. After running the engine to reach operating temperature plus 10 minutes or so, then letting it cool overnight, checking the coolant level will show it has lost around a quarter of a cup of coolant ... sometimes a little more. This adds up over a week or so, of course. No leaks appear apparant anyware and even removing the 'protector' under the engine shows no coolant on the floor. Obviously there must be a leak somewhere but goodness knows where. Any help would be appreciated. Thanks

29th March 2022, 07:11	#2
SD1too Doesn't do things by halves Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model. Join Date: Mar 2007 Location: Former Middlesex Posts: 20,372 Thanks: 1,587 Thanked 3,749 Times in 3,181 Posts	Hello Pieter, Check that the special KV6 refilling and bleeding procedure was carried out by the book. Simon __________________ "Whatever is rightly done, however humble, is noble." Sir Henry Royce.

29th March 2022, 07:18	#3
Bob Walker Loves to post MGZT Join Date: Aug 2019 Location: Richmond Posts: 255 Thanks: 26 Thanked 80 Times in 45 Posts	Coolant pipe under the radiator Hi Pieter Have you replaced the coolant pipe under the radiator with a stainless steel one? Another cause could be the coolant cap! They do deteriorate! Bob

29th March 2022, 11:29	#5
roverbarmy This is my second home Roverless + 1.7D Sportage Join Date: Aug 2014 Location: East Norfolk Posts: 7,050 Thanks: 729 Thanked 2,021 Times in 1,449 Posts	When you say "correct mark/s", are you just filling to the "MAX" mark, which is right at the bottom of the visible section of the header tank (You can actually see the word "MAX" printed on it). Filling any higher will just pressurize the header tank and the excess coolant will dribble out of the pressure vent. __________________ Oil in my veins!

29th March 2022, 22:12	#10
pieterm Regular poster Rover 75 Connoisseur SE Join Date: Mar 2018 Location: Point Cook, Australia Posts: 83 Thanks: 69 Thanked 8 Times in 6 Posts	Thank you everyone for your helpful replies. This has to be the most annoying thing yet LOL. I check the coolant each morning and note it has dropped from the MAX mark. I top it up only to find the same thing the next morning. If I leave it a few days, it will drop from the MAX to the MIN marks. The weird thing is some mornings it will drop from the MAX to well below the MIN mark! I have pressure tested the system and it holds the pressure even after an hour. This one has really got me beat.