Hydraulic roof fluid

The Hydraulic hood repairs feature in the November 2018 issue of CM highlights the importance of renewing the hydraulic fluid in the Jaguar XK100 hood mechanism every six years. My car is the next-generation 2007 XK150 4.2, which has a different hood mechanism, but still employs a hydraulic pressure pump. Unfortunately, I can’t find any instructions on how to renew the fluid in my car. Len de Jong

From the data I have, the hydraulic fluid in your XK150 should be Pentosin CHF 11S. This was an update from the earlier fluid used, which was Univis. It should not suffer from the earlier problems. There is a bulletin which specifies to use only Pentosin fluid JLM21112 to top up or refill any XK series roof system.

The basic steps to renew the fluid are as follows: 1) Remove the luggage compartment carpet and liners on the front and right-hand side. Power the roof to fully open and turn off the ignition. Disconnect the battery. 2) Unbolt the pump assembly and open the manual tap (approximately three turns).

3) Being careful with spillage, remove the reservoir filler plug and invert it over a suitable container, allowing the fluid to drain out. 4) Now raise and lower the roof slowly by hand six times. This will expel most of the fluid from the system. 5) Once the fluid has drained, refit the pump to the body and close the manual tap. Fill the reservoir to the upper limit on the tank. 6) The header rail trim panel then needs to be removed and you follow the steps as carried out in the CM feature in the November 2018 issue to drain the hoses. With the ignition on and the roof switch operated in both directions, the fluid can be flushed through the hoses before reconnecting them. 7) Once everything is back together, the pump tank can be replenished and the roof operated to bleed the system, ensuring the level of the tank is kept topped up.