Greg,
I had a failed vacuum advance in my 1990 V12 Vanden Plas (same 5.3L V12 and Lucas ignition as the non-Marelli XJ-S) and fixed it last year. Not only was the engine running hotter but my fuel economy dropped off significantly. I tested the vacuum advance with my MityVac and it was not working so I removed the distributor and rebuilt it with a working vacuum advance that I harvested from a spare V12 distributor that I had on hand, and then reinstalled it and set the timimg. The rebuilt distributor made quite a difference in the lowering the coolant temperature and raising the fuel economy.
Thanks for the suggestions. My aux fan actually runs all the time when the climate control system is turned on (despite the aircon radiator its designed to cool being missing at the moment!) so I know it works, I can hear it each time I turn the ignition on!
I have tested applying vacuum to the vac advance and observing the rotor moving, though that was 6+ months ago, so perhaps its worth me checking that again…
I swear every time I fix anything on this car, something else breaks!
Yes I have an infra-red temperature gun, but it isn’t doing it at idle. I am increasingly thinking that Doug may be correct and I may be seeing temperature spikes due to air/steam in the coolant…
Not aware of vacuum leaks - vacuum seems okay on my gauge.
No unusual noises when shutting down that I’ve noticed.
What I have noticed is I can’t run it for long at all with the crossover filler cap off, even when it’s cold, as the level rises up and then it overflows the filler neck - is that normal? I’d assumed it was just the water pump pressurising it?
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
25
Well, yes and no. It’s controlled by coolant temp, yes, but coolant temp coming out of the rad. If the rad was sufficiently cooling the coolant, it wouldn’t come on no matter what the engine is doing.
I have indeed noticed that since the new radiator and the fan clutch, the aux fan doesn’t come on at all unless the climate control is on, and that the temperature of the water leaving the radiator is much lower than it was previously!
Do any of you fine folk have a suggestion on what timing strobe gun to buy?
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
27
I was gonna ask that, too. How sure are we that this isn’t just a gauge issue?
That cap is on the suction side of the pump. You have a blown head gasket.
Matt,
I was thinking some more about your problem and the distributor problem I had last year with my 1990 V12 Vanden Plas and remembered that I had three symptoms, lower fuel economy, higher coolant temperatures, AND lower power. The reduced power was subtle until I rebuilt the distributor, installed it, and set the timing. The acceleration up hills near my house during the first drive afterwards was like night and day compared to recent drives in that car on the same hills. I didn’t realize what I was missing. After thinking about this more my first suspect is a failed distributor advance, or related timing issues. Of course I still recommend that you visually check to make sure that your aux cooling fan is on with the coolant tempetature above the “N”.
Greg makes a good point about checking the timing at the proper RPMs. Hopefully your shop that checked your timing followed the Jaguar Repair Operations Manual (ROM) procedures for testing and adjusting the timing.
I did wonder that, but the combustion gas check comes back clear every time… Hmm!
As for “Is it a gauge issue”, before I replaced the radiator I didn’t notice it doing this - the temperature would creep up at idle and slow traffic but be fine when cruising.
Now, the temperature is rock solid around town and at idle, but bounces around when I’m going fast or uphill…
Do you have pre-ignition? (Pinging) this can be caused by timing but easily by using too lower octane. Overheating and loss of power under load is typical.
Coolant Leak into the auto cooler (in bottom of radiator) and contamination of the auto oil…
I fill and bleed my cooling system on the flat. I also use a clear tube riser from the bleeding Hole.
I don’t experience any residual air problems. It takes about two to three times to get it completed.
Would a stall test help determine if engine power was down? Or the transmission dying.
Also, if it was retarded significantly it would run hot and be down on power (and the headers should start glowing under low load, right?). But make sure the cooling system is bled first.
I seriously doubt the transmission cooler can overheat the coolant!
Oh and yes consider the head gasket to be blown. If it blew the exhaust into the coolant, the sensor would see steam and eventually show the same behavior as with low coolant: it would go off the charts and then cool down very quickly when the water level comes back? Leakdown test time.
I did a compression test a year ago when I bought the car - most cylinders were 200psi apart from one that was 175psi, hence me buying the kit for detecting combustion gases in the coolant, but it indicated none so I pressed on…
Guessing if it is the HG, that’s not going to be a fun job…
What I do, and I think others as well, is to “tee” into the rubber section of item #11. If your confident of the installation you could leave the tee in place after testing. Otherwise replace the hose.
