Hi Grant, thanks for the doc. I can now fully understand how the thermostats are supposed to work.
I am currently rebuilding a 1986 XJS V12. In going over the cooling system I have found that the bypass ports in both thermostat housings are neatly blocked by welch plugs in a way that looks factory made. I have also found that both old and new thermostats are 3 to 5mm short of blocking the bypass ports anyway. What do you think I should do about this?

 

If you have an HE engine, then those blanks should be removed and the correct thermostats fitted.

 

1) Alcohol, lots of it, DAMN.

2) I answered your Private Message not long ago.

3) Find the Wombat that did that and string him up.
SuperCheap, Bursons etc etc.

Obviously REMOVE those plugs.

 

Thanks for the advice Grant. I will probably have to drill them out.
Regards,
Vadim.

 

Thanks Greg, will do.
Regards,
Vadim