My 07' 2.7 Range Rover sport has symptoms as follows:
Higher than normal coolant pressure
Air / coolant returning to expansion tank via thin pipe going to tank
Pressure causing coolant tank to leek coolant

There is no oil in water/water in oil
No misfires, no white smoke from exhaust
No overheating
No warning lights on dash

Car is driving fine apart from a little hesitant on acceleration but pulling fine after a couple of seconds from hitting the throttle,
There is air bubbles in the coolant return constantly and I thought initially head gasket but have flushed the system and performed sniff test twice and test is normal (test fluid remaining blue and never turns yellow after 15-20 minutes running)
I'm completely stumped as to what could be causing the air to get into the cooling system, any ideas as to what my next move is would be greatly appreciated, also I might add that code p0100 is present when I run diagnostics (Maf issue that won't clear)

Also I might add there are no other coolant leeks apart from when I run the engine and pressure forces a little coolant out of the expansion tank cap.

Thanks in advance for any help.

often a new tank cap is suggested

loonyball wrote:

My 07' 2.7 Range Rover sport has symptoms as follows:
Higher than normal coolant pressure
Air / coolant returning to expansion tank via thin pipe going to tank
Pressure causing coolant tank to leek coolant

There is no oil in water/water in oil
No misfires, no white smoke from exhaust
No overheating
No warning lights on dash

Car is driving fine apart from a little hesitant on acceleration but pulling fine after a couple of seconds from hitting the throttle,
There is air bubbles in the coolant return constantly and I thought initially head gasket but have flushed the system and performed sniff test twice and test is normal (test fluid remaining blue and never turns yellow after 15-20 minutes running)
I'm completely stumped as to what could be causing the air to get into the cooling system, any ideas as to what my next move is would be greatly appreciated, also I might add that code p0100 is present when I run diagnostics (Maf issue that won't clear)

Also I might add there are no other coolant leeks apart from when I run the engine and pressure forces a little coolant out of the expansion tank cap.

Thanks in advance for any help.

Get the pressure measured at idle and while at 1500rpm.

No problem, if its not a stupid question, what am i looking for.
Thanks for your’e input 👍

How do you know the pressure is high and not something else?

Did you follow Andy's advice?

Next,
Coolant tank can crack, so fine it's hard to spot, wipe and look.

Take the little things first
before we start on Horror radiator or engine troubles

Hi rover75, thanks for taking the time to reply, pressure is high because when the car has been driven ten miles or so, the pressure builds and vents through the cap, also new tank and cap already fitted, basically, the problem is air in with the coolant returning to the expansion tank raising pressure. As stated previously twice i have run the sniff test which has proved negative, i really have hit a brick wall with this issue.

once system is bled and without airlocks, the only air possible is from exhaust in waterways.
head gasket and or warped head.

As said you better have the pressure testet
are your thermostat & water pump in order?
is there enough coolant on? your 10 mile drive before it gets up could indicate to little coolant / incorrect filling.
has it been filled correctly and bled?
has the new tank and cap ever kept tight?

hopefully you just have an airlock and or another bad cap.

Last edited by rover75 on Mon Jul 01 2019 9:53pm. Edited 1 time in total

Hi, don't know you but here's the text from the workshop manual,
do it wrong and you can end in overheating/leakage troubles,
ignore if you already know

Raise and support the vehicle.
2. Set the heater controls to maximum.
3. Disconnect the battery ground cable. (you don't have to disconnect)
4. Remove the engine cover. For additional information, refer to: Engine Cover - TDV6 2.7L Diesel (501-05 Interior Trim and Ornamentation, Removal and Installation).
5. WARNING: Since injury such as scalding could be caused by escaping steam or coolant, do not remove the filler cap from the coolant expansion tank while the system is hot.
Remove the coolant expansion tank cap.
6. Remove the radiator access panel.
Remove the 4 bolts.
7. Position a container to collect the fluid.
8. CAUTION: Engine coolant will damage the paint finished surfaces. If spilt, immediately remove the coolant and clean the area with water.
Release the clip and disconnect the radiator lower coolant hose, allow the coolant to drain.
9. Remove the container.
10. Connect and secure the radiator lower coolant hose.
Secure with the clip.
11. Connect the battery ground cable.
12. Connect exhaust extraction hoses to the tail pipes.
13. Loosen the coolant expansion tank bleed screw.
14. Loosen the cylinder head bleed hose bleed screw.
15. Fill the cooling system, keeping coolant to the upper level mark of the expansion tank.
16. Tighten the bleed screws.
17. Install the coolant expansion tank cap.
18. Start and run the engine.
Hold the engine speed at 3,000 RPM for one minute.
Return the engine to idle for five minutes.
Hold the engine speed at 3,000 RPM for one minute.
Run the engine until the thermostat opens
19. WARNING: Release the cooling system pressure by slowly turning the coolant expansion tank cap a quarter of a turn. Cover the expansion tank cap with a thick cloth to prevent the possibility of scalding. Failure to follow this instruction may result in personal
injury.
• NOTE: When the coolant bleed is complete and prior to installing the expansion tank cap, top-up the expansion tank to 30mm above the maximum level.
Switch the engine off.
Remove the coolant expansion cap, allow the level to settle and top-up so that the level is 30mm above the upper level.
Allow the engine to cool.
20. Install the engine cover. For additional information, refer to: Engine Cover - TDV6 2.7L Diesel (501-05 Interior Trim and Ornamentation, Removal and Installation).
21. Clean any spilt coolant from the vehicle.
22. Install the radiator access panel.
Tighten the 4 bolts to 10 Nm (7 lb.ft).
23. Check and top-up the coolant if required.

just to follow on the issue i have with my car, i read somewhere on another forum someone had very similar symptoms as mine but it turned out to be a faulty egr cooler allowing exhaust gases get in to the coolant inside the egr cooler, i'm curious as i would have thought the pressure in the coolant system (under normal conditions) would have been higher than the exhaust pressure within the egr cooler ? maybe i am wrong, but i also got to thinking that if the exhaust gas WAS leaking into the cooling system via the egr cooler would that not show in the sniff test ??

Yes.

And normally coolant leaks out egr coolers

I am having a very similar issue and have changed
Egr cooler
Thermostat
Water pump
Coolant tank
Coolant cap
Radiator
Etc
When I rev my coolant level drops also and returns after
My coolant level drops when hot and then once car cools down it rises
Did you fix your issue ?

No i have not found any fix for my car, it has got me totally stumped, i am convinced its not a head/gasket issue.
The persuit of a cure continues.....

Have you replaced all of the pipes?

I'm not sure if this is possible (expecting to be laughed at) but if a pipe has a micro split in a part of the system which is under vacuum rather than presure (assuming just before the pump?) then this would suck in air rather than push water out.

can you add presure from the expansion tank to check whilst the engine is off but warm to ensure the thermostat is open..?

That would make sense , howether it has been pressure tested how can I test this ? As coolant system is already pressurised and not leaking so surely nothing will come out of the potential vaccine pipe ...