Is it possible for the DCCV to leak only when the temp is at a higher setting like around 80 deg.? I have a leak after I increased the setting so is it possible for it to stop leaking on a lower setting?

I increased the setting because the normal setting of 72 deg. was fine at first then turned cooler after a while so I kept increasing the temp until the air got warm again. It got too hot at 80 so lowered it. Right after this is when it started leaking from the DCCV area and I have not driven it since so just wondering if it would be safe to drive with a low temp setting.

My "old school" thinking related to a leaking heater core when we would turned the temp to cold to shut off the water to the core therefore stopping the leak just might not apply here, so just asking.

 

My thinking is that simply increasing or decreasing the HVAC temperature setting in the cabin would not cause a leak at the DCCV. However, as unpredictable as these DCCVs are after years of operation, any movement of the valves inside the DCCV may indeed be enough to trigger a leak. Have you closely inspected your DCCV to verify that your coolant leak is indeed originating there?

 

Jon89, no I have not had the DCCV looked at closely so I suppose it might be a hose leak. My question is more related to driving it to my garage as safely as possible.

 

Just as likely to be the radiator if the DCCV is mounted in the same location on the V8 as it is on the 3.0L. IIRC, the radiator is common to both engines, but I am unsure as to DCCV location. The radiators are prone to leak in a spot that blows directly back on the DCCV in the 3.0L.

 

Don't know about the different settings causing the leaks.

From my experience, Joyce's Jags DCCV dripped small amounts of coolant on and off for about a month or so before having a continuous leak.

The ZF electrical sleeve o-ring will do the same as many have reported over the years. Would one dare to say "it's a Jag thang".

 

Depends how far away your garage is....but both the DCCV external leaks (they can leak internally, too...causing unwanted heat) and the radiator leaks I've experienced were not of sufficient magnitude to cause "Coolant low level" warning for several hours of run-time.

Heck....even the most recent tank-turret leak survived a couple weeks of daughter's daily-driving and the jaunt from NE Louisiana back to NTX with only the occasional minor top-up with distilled.....naturally...as soon as I disturbed the air around it with a finger...it popped off straightaway....

 

The first thing that I would do is make sure the cooling system doesn't have too much pressure. The cap on the coolant reservoir controls the pressure. When the car is running and up to temperature you should be able to easily squeeze the large hose on the top. If it's hard to squeeze, it has too much pressure. A new Jaguar cap is only ten dollars or so and should have a tiny hole in the middle. I didn't know this before and with my car I had to replace my DCCV and thermostat housing which failed prematurely as many others probably have. A new cap is a good investment.

 

Good input Catmobile, I have replaced both the thermostat housing and lower hose not many miles ago and now I am wondering if they were caused by a faulty pressure cap. If there is a leak, even if caused by a faulty cap, wouldn't the leak stop the pressure from building?

 

Yes Brutal one of our factory techs has suggested this in the past. If the cooling system is marginal or has a small leak and you want to get by with it for awhile. I would leave the cap unscrewed just enough so you don't have an air-tight seal. This will insure you have 0 psi in the cooling system.

Now remember if you do this you can't keep the cooling system full because as the coolant heats up and expands it will **** some out. After several heat/cool cycles the car will find the coolant level that it's happy with. So you will have some room in the expansion tank when the car is cooled off.

Not a permanent repair but will avoid pressure on those weak plastic cooling parts!

This is exactly how the old car cooling systems work. I am working on a 1949 International pickup and it has a zero pressure cooling system with a non-pressurized radiator cap. Several guys have blown the freeze plugs out of the block when they installed a modern 15 PSI radiator cap!
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If you haven't, just get a new cap and then you can screw it on all the way.

 

Update - I took Catmobile's advice and Started the engine and got it up to temp. with the cap on tight and fluid full. The top hose was not hard and easy to squeeze and better yet there were no leaks visible anywhere. I don't know how this happened because I had a small leak and got the low coolant warning the last time it was driven a few weeks ago. I have driven it twice on short trips of about 150 mi. round trip and still no leak. I also have not changed the temp setting from the 74 - 76 degree range so no major change has been required to the DCCV.
I also ordered a new pressure cap from SNG Barrett just to be safe and it came yesterday. I noticed the new cap is rated at 140 kPa (what ever that stands for) but the cap on the car is rated at 120 kPa. Any real danger in using the new cap? Anyone know what rating is suppose to be used?

 

Yes they changed the label and 140 kpa is about 20 psi. Which I think is VERY high for a cooling system pressure!

Don't know why the change.
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That is why I asked as I am concerned that more pressure is not a good thing for a 12 year old car with 120K miles. At my age, I take these things sort of personal as it would be like raising my blood pressure and not expecting any consequence.