My 2010 Jaguar XK 5.0 Non Supercharged engine has a coolant reservoir cap rated at 200 kPa which is equivalent to close to 30 lbs. This is the factory cap that came with the car from new. I did change it once. If performing a coolant pressure test at the reservoir, what would be the suggested pressure to pump into the reservoir tank? I feel that 30 lbs is excessive and was planning on 15-17 lbs. Any feedback would be greatly appreciated.

 

Think I used 14-15 psi.

 

Kj07xk........I believe when you did your test your reservoir cap was rated at 120 kPa which equates to 17.4 lbs My cap is 200 kPa which is closer to 30lbs. Shouldn't I be pressurizing my system to a higher number than 14-15 (do to my 200Kpa cap) to get a more accurate outcome? There must be a reason Jaguar is using a 200kpa reservoir cap now instead of the previous 120 kPa cap. Also, your car is a 4.2 and mine is a 5.0 Thanks.

 

15 - 20 psi would be fine for a leak-down test to check for loss of pressure. In fact, you could probably use half that and still see a pressure drop if the system has a leak.

I would probably start at 10 psi and see if that holds. If it doesn't then there is no need to go any higher. If it does hold, then try 15 psi. If that holds, the test has been passed.

Richard

 

The increased PSI for the latest JLR engines was due to higher operating temps and thusly the "need" for higher pressure cooling circuit to reduce the coolant boiling point. I think for each 1 PSI, boiling point's reduced by 3 degrees.

 

Thanks jahammer for your imput. Yes, I am aware that supposedly the increase in the PSI on the reservoir caps are due to decreasing the boiling temps in order to protect our engines. There have been various discussions on this matter on how the increase in pressure can negatively affect our fragile plastic cooling lines, especially those with the seamed variants that have been vulnerable all along. I just wanted to make sure that I wasn't "pushing the envelope" when it came to increasing the pressures more than necessary for coolant pressure testing. Thanks again for your feedback.

 

If you're looking for coolant leaks, there is no need to go much higher than 1 bar with a cooling system pressure tester.

 

I don't HAVE any pressure in my coolant system. The reservoir cap merely holds the liquid from spilling and eliminates airborne contamination.
Is that okay???

 

1 Bar = just over 14.5 psi

 

My concern with pure glycol based coolants is they aren’t as effective at cooling cylinder temps (heat’s also a JLR engine killer), they’re flammable (flashpoint of 225 degrees F) and they turn tyres into ice skates…. As such they’re prohibited from Motorsports use.

 

Ethylene glycol is indeed gross stuff. Propylene glycol is not nasty as it dissolves easily with water and is non-toxic.. Evans is approved by the NHRA, AHRA and other racing bodies. That's one reason I use it in my P/S Mustang II.

 

I recently discovered that my 2012 XK X150 had a 200 kPa cap installed. However, the 2012 owners manual, workshop manual and the parts tech at my local dealer indicate that 140 kPa is the correct value. I’ve heard the rumor that Jaguar raised the value to 200 kPa, but have not found support for that in any TSB.

Given the known issues with the PA12 coolant hoses deteriorating after 6 to 8 years because of exposure to temperatures above its 185 degree working limit, I’ve chosen to replace the cap with one rated at 140 kPa. I also changed my coolant mix to 55/45.

Its my understanding that the XKR uses a 200 kPa cap, but the supercharged engines were designed to do that.

 

Its not just heat and age that causes the deterioration. Aged fluid won’t help either as it gets contaminated and its pH will change.
Anyways, good call on your maintenance regime!