So, I was trailering my new to me 04 vdp (x350). While under it to hook up chains I saw a pretty constant coolant leak. I couldn’t get under it far enough to see what it actually is leaking. My first thought was the heater core. It’s passenger side near the firewall. So I started researching R&R heater core

Then I learned about something new to me

“auxiliary water pump for the heating system”.

I’m really new to this model so I started to wonder; where is this pump and could it be the source. Haven’t found much so far so any help appreciated. Also considered the heater control valve may be leaking. Location of that would be helpful as well.

it’s kind of chilly right now so I’m researching before I get too deep into anything physical.

so, to the knowledgeable members here; best guesses what I’m going to find.

When you open the bonnet, the auxiliary water pump should be to the left side of the radiator, underneath the cooling expansion tank. It is an electric pump.

Best regards,

Thomas

There is no heater core valve, as interior heat is controlled by air baffles in the air stream from the core to the vents. There is always full coolant flow through the core, which is the case with most cars these days. The hoses to the core are on the passenger side firewall. The hoses are actually metal pipes with short hose sections to join the pipes to the core, or to the cooling system at the front.

The auxiliary pump is mounted to the fan shroud at the radiator, so if your drip is at the back, that's not it. Assuming that you've removed the lower aero panel under the engine. If that panel is still there, then you won't see where the drip is coming from, just that it's coming from the back edge of the panel.

Another possible source of dripping at the back, which would not be a good thing at all, is a leak from the valley hose which runs under the intake manifold. A leak from that would pool in the valley of the engine and run off the back. I say "not a good thing" because that hose requires removal of the intake manifold for replacement, and even for checking, which is not an insignificant job.

Well let’s hope it isn’t “that hose”. Nope, haven’t pulled any covers/panels yet.

the curious thing is I was told the owner had driven the car probably half a day’s drive (and had a stroke and passed while there) with his friend driving it back home. That suggests the leak literally started when I started it to trailer it.

but since I literally got it yesterday, as much as I want to take it for a ride, I know it’s not going to be an instant road trip.

thanks for the info. This site has an impressive group of jag fans. I am amazed at the technical knowledge posted throughout the forums I’ve been reading. I appreciate all those willing to share.

A drip will be almost impossible to find visually, as crowded as the car is under the hood. I had a coolant leak which started slow, got serious enough to need some coolant every few days and I could not trust the car for trips of any length. When the car was warmed up, I could see steam, but not where it was coming from. Turned out to be a crack in the radiator side tank, and it took going to a shop for a pressure test to find it.

Coolant leaks when it's hot and under pressure, and any drips you see are simply from the puddling that occurs after the car cools, and are not really any indication of where the actual leak is happening, especially if it's just water running off of the underbody cover plate.

Buy an inexpensive pressure test kit for about $50.

I have chased many coolant leaks down on my car over the years. I too had drips in the rear passenger side of the engine compartment. I checked the lines mentioned in the posts above but couldn’t find the source. Put car on lift, took off belly cover and with the car started saw the drip and still couldn’t find the source. Finally found a tiny stream shooting from the coolant expansion tank bottom at the perfect angle hitting the back/middle of the wheel well area and running down hidden over the frame. Couldn’t see it with the naked eye, but when your hand interrupted the flow it was obvious. Good luck.

[QUOTE=NDW;2807304]I have chased many coolant leaks down on my car over the years. I too had drips in the rear passenger side of the engine compartment. I checked the lines mentioned in the posts above but couldn’t find the source. Put car on lift, took off belly cover and with the car started saw the drip and still couldn’t find the source. Finally found a tiny stream shooting from the coolant expansion tank bottom at the perfect angle hitting the back/middle of the wheel well area and running down hidden over the frame. Couldn’t see it with the naked eye, but when your hand interrupted the flow it was obvious. Good luck.[/QUOTE . That sounds like one seriously frustrating leak you had.

As I learn more, what I’m suspecting is when I put the car on the trailer it tipped the nose up enough to cause pooled coolant in the valley to run out the back of the upper engine area. Before I learned of the valley hose my first suspicion was the heater core had crapped out and the leakage was running from a heater box drain but the more I read the more likely it sounds like a valley hose or other parts in the valey area.

I don’t have a garage to work in and it’s been crappy outside wrenching weather so I haven’t really gotten into the actual work yet.




does anybody know if one could use a borescope (endoscope, inspection camera, whatever one calls them) to view the hose under the intake?

Chasing coolant leaks is a PITA, but I've had good luck using a Mityvac MV4560 Cooling System Pressure Test Kit. If I cannot see what is leaking I use a dye kit found at most all auto parts stores. If the leak cannot be found from the top of the engine bay raise the car and set it on jack stands. It usually takes about 10-12 PSI for the leak(s) to present themselves. Good luck.

thanks for the suggestions.

was the dye you suggested fluorescent by chance? That would surely benefit in the limited view situation of trying to see in the suspect area.

I did try using a borescope to try to view under the intake manifold. It wasn’t a very good scope so my view was very limited. I did see some “gunk” I suspect is leaked coolant on the valley floor. I think there’s no real alternative other than just pulling it apart and making sure what is and isn’t leaking in that area.

Yes, it is a fluorescent dye. Use yellow goggles to round out the kit. Sorry for the lack of full information.

no problems at all. I appreciate the input and as always on a forum, we can always ask for clarification.

Congratulations on your new Jaguar! Its a shame you're getting to grips with repairs first.

If it turns out that it is the valley hose, maybe the this short article might help. I wrote this for the the club magazine after fixing mine in April.

https://www.sdjagclub.com/Newsletter

Its the November / December issue - page 35

Its easy DIY - expensive if you pay for labor.

HTH, Dave

PS - with hindsight I could have confirmed the leak location beforehand. The leak was at the bend next to the throttle body. No endoscope needed.

thanks a lot Dave. Yes I was a bit disappointed I had to do some repairs before driving it but not too bummed. I used to be a wrench jockey (not jag or even a dealer unless you want to count the Clark forklift dealership I used to work at) many many years ago so this sort of work is not out of my wheelhouse. I’m also retired so I’m not pressed for time.

I already have the intake gaskets. The rest of the parts (including some I may not need but will have on hand if needed) will be here shortly after Jan 1.

to all who have jumped into my thread; thanks. It’s great to see a group that’s so helpful.