Air lock in radiator ..help

chambl01 · 3rd October 2015, 08:36

Hi everyone, I've just renewd antifreeze in my Rover 75 2.0 CDT se Connie. Unfortunately I've since found my rear vent is freezing. On further investigation I noted the lower left radiator tube very cold whilst the top right tube very hot. Clearly an air lock. I tried purging the tubes to move any air out with no avail. Tried the air valve but only antifreeze dripping out. I'm worried I can't use the car until I get the lock out as i don't want to damage the engine. Any advice would be greatly received. Thank you

T-Cut · 3rd October 2015, 10:18

Quote:

Originally Posted by chambl01

- - - I've since found my rear vent is freezing.

Do you mean the fresh air vent/grill for the rear passengers? If so, it only provides cold/ambient air.

TC

stevestrat · 3rd October 2015, 10:24

Yeap, heat comes through ducts under the front seats, the vent on the rear of the centre consul only does fresh air from outside.

SD1too · 3rd October 2015, 11:33

Quote:

Originally Posted by chambl01

... I noted the lower left radiator tube very cold whilst the top right tube very hot. Clearly an air lock.

Maybe, but with such a marked temperature difference your thermostat may be stuck closed. That would be unusual though; the diesel 'stats commonly have the opposite problem.
I'd suggest that you activate the instrument pack diagnostics to find out the actual temperature which the coolant is reaching. That will aid your diagnosis.

Quote:

Tried the air valve but only antifreeze dripping out.

Here's the official MGR venting method. Note that the bleed screw should not be opened with the engine running.

Simon

chambl01 · 3rd October 2015, 17:58

Quote:

Originally Posted by T-Cut

Do you mean the fresh air vent/grill for the rear passengers? If so, it only provides cold/ambient air.

TC

I'm sure it was heated, maybe I'm wrong. But still confused as to why the bottom large radiator hose is so cold when all the others are hot. I assume circulating hot water would be demonstrated by both intake and output hoses in and out of the radiator. I was wondering whether their was an airlock in the main radiator itself.

T-Cut · 3rd October 2015, 20:37

Hot coolant goes into the radiator at the top. It gets cooled on the way down, so it comes out cooler at the bottom. It shouldn't be stone cold though. Are you sure it's not simply cooler than you expected? A common issue with diesels is the premature opening of the thermostat. This has been discussed at length and is well understood. It means flow into the radiator starts much earlier than it should. That means coolant at say 75C from the head is allowed into the rad. It will make the top hose feel 'hot' but will actually be over-cooled by the rad and so feel much cooler than it should be on exit. It's the reason why so many diesel owners have fitted the in-line thermostat mod. Your engine needs to be running at around 90C. The chances are it's 20 degrees cooler.

The rear passenger section vent/grill only ever supplied cold air. It's not connected to the warm air system. Warm air is delivered through pressed steel ducts moulded into the floor and exit under the front seats.

TC

chambl01 · 3rd October 2015, 21:23

Thank you, that sounds great. I was worried about driving the car but sounds like everything s normal then. I've just not paid any attention to it before. I'm sure I'll pass on my experience to others on the forum. This site is fabulous and members who reply my superheroes. Thanks everyone, all this info is great. Very much appreciated.

first-things-first · 3rd October 2015, 23:10

My rad in colder months is roasting hot at the inlet (top left pipe from front of car) and warm (can hold your hand there for as long as you like) at bottom right of rad.

In summer months it gets uniformly roasting hot all over. I think the rad is over specced for diesels and so only gets given a workout in the hotter months / climates.

chambl01 · 4th October 2015, 08:57

Quote:

Originally Posted by first-things-first

My rad in colder months is roasting hot at the inlet (top left pipe from front of car) and warm (can hold your hand there for as long as you like) at bottom right of rad.

In summer months it gets uniformly roasting hot all over. I think the rad is over specced for diesels and so only gets given a workout in the hotter months / climates.

Left top gets hot lower right cold. Heating inside the car is fine though. Wish their was an air valve in the radiator not just the heater matrix hose.

T-Cut · 4th October 2015, 09:46

Have you checked the running temperatue?

TC

3rd October 2015, 08:36	#1
chambl01 Avid contributor Rover 75 Join Date: Aug 2014 Location: Cardiff Posts: 162 Thanks: 151 Thanked 75 Times in 28 Posts	Air lock in radiator ..help Hi everyone, I've just renewd antifreeze in my Rover 75 2.0 CDT se Connie. Unfortunately I've since found my rear vent is freezing. On further investigation I noted the lower left radiator tube very cold whilst the top right tube very hot. Clearly an air lock. I tried purging the tubes to move any air out with no avail. Tried the air valve but only antifreeze dripping out. I'm worried I can't use the car until I get the lock out as i don't want to damage the engine. Any advice would be greatly received. Thank you Last edited by chambl01; 3rd October 2015 at 08:58..

3rd October 2015, 10:24	#3
stevestrat This is my second home ZT260 #243 (resting) Join Date: May 2010 Location: Prestonpans Posts: 22,562 Thanks: 650 Thanked 4,624 Times in 3,358 Posts	Yeap, heat comes through ducts under the front seats, the vent on the rear of the centre consul only does fresh air from outside. __________________ Steve T4 Location Map

3rd October 2015, 20:37	#6
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,754 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	Hot coolant goes into the radiator at the top. It gets cooled on the way down, so it comes out cooler at the bottom. It shouldn't be stone cold though. Are you sure it's not simply cooler than you expected? A common issue with diesels is the premature opening of the thermostat. This has been discussed at length and is well understood. It means flow into the radiator starts much earlier than it should. That means coolant at say 75C from the head is allowed into the rad. It will make the top hose feel 'hot' but will actually be over-cooled by the rad and so feel much cooler than it should be on exit. It's the reason why so many diesel owners have fitted the in-line thermostat mod. Your engine needs to be running at around 90C. The chances are it's 20 degrees cooler. The rear passenger section vent/grill only ever supplied cold air. It's not connected to the warm air system. Warm air is delivered through pressed steel ducts moulded into the floor and exit under the front seats. TC Last edited by T-Cut; 3rd October 2015 at 20:45..

3rd October 2015, 21:23	#7
chambl01 Avid contributor Rover 75 Join Date: Aug 2014 Location: Cardiff Posts: 162 Thanks: 151 Thanked 75 Times in 28 Posts	Thank you, that sounds great. I was worried about driving the car but sounds like everything s normal then. I've just not paid any attention to it before. I'm sure I'll pass on my experience to others on the forum. This site is fabulous and members who reply my superheroes. Thanks everyone, all this info is great. Very much appreciated.

3rd October 2015, 23:10	#8
first-things-first Posted a thing or two MG ZT Join Date: Jul 2014 Location: Hornchurch Posts: 1,255 Thanks: 176 Thanked 352 Times in 272 Posts	My rad in colder months is roasting hot at the inlet (top left pipe from front of car) and warm (can hold your hand there for as long as you like) at bottom right of rad. In summer months it gets uniformly roasting hot all over. I think the rad is over specced for diesels and so only gets given a workout in the hotter months / climates.

4th October 2015, 09:46	#10
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,754 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	Have you checked the running temperatue? TC