Ok. I was getting in the spirit to show my 2004 XK8 at the local Jag Concours. So, thoughts of cleaning the engine bay came to mind. Knowing that these cats do not like water, I first resisted. But, hey... "I" am a professional mechanic. I should be qble to keep the water from getting into places it isn't welcome! So, I hit it with the pressure washer at work. An outstanding job of cleaning, and she started right up afterward! Lovely! Oh, wait. I noticed my A/C was performing poorly, particularly at idle or low speeds. I kept watching the temp gage, and it was normal at all times. After stopping at a friends, I drove off and the temp gage then crept steadily up until the overheat warning came on. Of coourse, i pulled over immediately, and popped the hood. All looked fine. I restarted the engine, and the gage read normally, so I drove off. The situation repeated itself once again. I pulled over again, looking for any explanation. All looked ok. I drove off again noting my temperature was again normal. This time the situation seemed to resolve itself, and I drove the car a bit during my weekend, being wary of my situation. My initial diagnosis was that I was bitten by the thermostat bug, and I replaced it that following work week. After refilling the system and watching carefully, it finally dawned on me that the fans were not coming on. Mine have never come on much during our mild winter days here, but the a/c still wasn't up to par. Finally, I started to do some probing, and the fan circuit was dead. No power. I found the 80A fuse mounted to the left side shock tower was popped; probably as a result of my washing. My dealer had to order the fuse, stating they had never sold one! Lesson 1: Not a good idea to spray water directly onto these engines. Lesson 2: If you do, check EVERYTHING. Lesson 3: As we all know, these "gages" are not really gages. But they will fool you into being complacent. Lesson 4: When something seems amiss, such as my a/c acting funny, PAY ATTENTION. I could have easily hurt my engine had the outside temperature been warmer, and I would not have realized it! I should have looked harder for a problem when I first noticed an issue. No harm done, but I went through a week of mixed emotions over something very simple! I hope someone benefits from this post. Sorry it was Soooo long-winded!

 

Good info. I've been washing my engines and engine bays since the mid-1970s with a spray can of Gunk or Engine Brite and a garden hose. But I have never washed under the hoods of either of our Jaguars and never will - too many flaky electronics to take a chance with....

My trusty 1999 Dodge Ram still gets its engine washed a couple of times a year, though. Never a problem soaking that truck....

 

The British don't worry too much about building waterproof electrics since their climate is so dry. I learned this over many years with several lovely Jags and MGs.

Besides, I'm still training myself to keep the outside nice and shiny. My philosophy is if it's nice enough outside to wash, then it's certainly a good day to drive. Not a hard choice to make for me.

 

Still wonder why the fuse blew; Mayby the fans got stuck as a result of corrosion or debris being washed in? Even salty water would not cause an 80 amp fuse to blow, so I would be suspicious of another root cause?