Hello forum,
after having read wfooshee‘s post about his coolant issues and the rather difficult way to solve it (Coolant Leak) I turn to you for some creative advice on a strange leak of my own.

Same as wfooshee describes my car has always lost some coolant. Some years ago I found the top hose connector on the expansion tank to be broken, changed the tank and all was good, until recently.

Strangely I only seem to lose coolant when doing short distance trips or when the car is standing !
When I top up, do 600+ km in one sweep and check the next morning the coolant level is perfectly at max, where it belongs.
But when I then take it out for only one or two short trips of maybe 5 .. 10km the coolant low warning comes up and I can refill up to 1.5 liters. Did this just this morning after I just drove shopping for groceries yesterday and had a short trip to a furniture store 2 days ago. Both about 10km roundtrips. Before the level was at max.

I try to get my understanding around the fact that the car doesn‘t lose a single drop on a hot 650km drive at around 130..140km/h and >30degC ambient, but gushes out liters of the good stuff without any trace when standing or doing a few short distances. Without any trace! I checked the oil, there is now sign of water in it, there are no puddles under the car, it seems to just disappear into thin air, and quite a lot of it. With a few trips through town I can refill up to 1.5 liters every other day. But take it to the Autobahn for a day and it finishes with max level.

Has anybody here who already crawled through the 4.2 NA cooling system encountered a special design feature that could explain this? I am hesitant still to just tear everything apart and replace it so that maybe the right part was among the exchanged ones.

Maybe the green one feels like a noble long-distance limousine that gets bored around town hauling lettuce and cases of beer, so it tries to make me use something different for groceries?

 

Mine was weird at first as well. I could take the car on a 700-mile round trip without having to top it up, or I'd have to top it up twice in a couple of days just running around town. I could smell coolant sometimes when driving just a short while, other times not for several days.

It did eventually reach the point that It would only go 10 minutes or so before a low coolant warning, and I could see it steaming under the hood, but it's so crowded under there I could never make out where it came from. A pressure test showed a crack at the pipe for the upper radiator hose, and I can only think that the crack was nearly nothing, and stayed nearly nothing, for quite a while, then suddenly it was significant enough to fail to hold pressure completely.

As you saw in my thread, my first effort was the expansion tank, which did not fix the issue. That's when I took it in for the pressure test. After replacing the radiator, it started a daisy chain of failing the next weakest component, with the expansion tank actually failing, then a serious leak at the water pump. I decided to forklift everything and ordered ALL of the hoses, one of which I'm still waiting for. I felt it would be simply stupid to replace the water pump and just see what blows next. It might have been fine, or I might have been tearing it down repeatedly, and just getting the fan assembly out so you can reach all of the hoses is enough of a job to make spending the significant money on all new hoses worthwhile.

Replacing the radiator was a VERY difficult job, far more difficult than I anticipated, because of the way the upper A/C condenser pipe wraps around it at the top, making it nearly impossible to clear the mounting tab for the fan shroud, and then the pipe for the lower radiator hose. Evecauating the A/C system and opening that pipe at the condenser would have mad short work of it, but I didn't know that before I started.

 

So you also had the effect that it could go for long trips without loss, but could lose lots of water on short commuting? Scary, looks like I also have to go the full way then and rip everything out. Ouch …

 

Find an indy who can pressurise the cooling system and search for leaks with a UV lamp

 

I wondered if perhaps it gets hot running around short drives due to the fan not turning on when it should. On the highway there is plenty of airflow to cool her without the fan running.

I recently replaced my expansion tank with a new one (Uro), most of the hoses, water pump and thermostat assembly and have still been seeing a puddle form under my car occasionally. Since I have a new radiator waiting I was not overly concerned, believing the aged radiator was the likely culprit. However today I topped off the coolant level then drove about 6 miles. I checked under the car when I parked, no leak. I then ran a few more miles of stop and go traffic then stopped at another store and checked again, still no leak. I then drove home roughly 5 miles. Pulled in the driveway and looked under the bumper to discover a few drops hitting the ground. It was quickly growing into a small stream of steady drips.

I popped the hood to see if there was any clearly visible leak from the radiator only to discover coolant flowing out from under the new cap on the expansion tank.
Why the cap that came with the new expansion tank only leaks sometimes strikes me as odd but that is what is happening. I would have thought maybe a sticky thermostat could be causeing it to run hot and build up to much pressure but that is not the case. I have had my code reader connected continuously while running around and I know the coolant temp never went above 197 F. That is with an outside temp of 100 - 105 I still have my original, Jaguar cap from my first expansion tank and will try it to see if there is any improvement. Hopefully there is not a defect with the tank itself.

Depending on how many miles your car has it may well be time to change out many of the coolant systems components regardless. On my 2004 NA, with the exception of the radiator and the valley hose it was fairly easy to do in an afternoon. Provided nothing seizes or breaks. Good luck.

 

Cracked thermostat housing.

I have put up with exactly the same symptoms. Initially, local Jaguar independant garage pressure tested, and blew the bottom of the radiator out. Simple, thought that was it..

Then little losses persisted.

Pressure tested. No leaks found.

Losses got more. Pressure tested again. No leaks found. Water pump replaced by Jag Indie.

Losses; very predictable. Quick dash to the shops and back, top up needed. Longer trip; no issue. Soon found out it wasn't burning off, as parking on an angled multistory carpark, left a huge red puddle. That's where all my Halfords coolant went. Suspicion of a smear from the expansion bottle overflow pipe. Not convinced.

Finally took it to a trusted MX5 specialist (race team). Straightaway they found cracks in the plastic thermostat housing, and send that exactly accounted for the behaviour. Until the thermostat opens up, coolant is going to **** out.

So belt and braces thermostat housing and new expansion tank ordered. Only Jaguar no longer makes the thermostat housing, and I am now seriously stuck. Jag says there is no stock in the UK. I might have a whiff of one at an indie parts supplier, but its frankly desperate now. Luckily, nothing has been dismantled, so the car is still driveable.

When pressure testing, pressure test when hot and when cool/ Jag Indie was pressure testing a hot engine, and so found no leaks.

At this point, I wish the Jag had been stuffed with more Ford parts.

 

My green one has passed 220.000 miles some time ago, so it is most likely time to change a lot of hoses and rubbers. The leaking cap is of course the wild dream of everyone losing coolant, easiest fix of all times but I’m not that lucky unfortunately. But most of that being possible in an afternoon is encouraging, thanks

 

Ispab, that sounds like exactly what my car has! I will check on the thermostate housing and hope that itˋs not only one of several possible reasons for this strange behavior.

As for the Ford parts, I absolutely support that wish for everything that is hidden somewhere. When I replaced the rear wishbone arms some years ago I got the Lincoln pair for half the price of only one official Jaguar part in Germany.

 

Short first update for those who may be chasing coolant gremlins too.

With my local indie we found a long crack in the expansion tank. Sprays quite impressively under a little pressure, but in a hidden position half on the bottom, not so easy to spot at first sight.
I had changed that tank already some years ago against an aftermarket part because the connector for the overflow hose had broken off, will change to OEM now.

Probably just a first step, there may be more to come, but let‘s see how it behaves after this first known leak is gone. Every hole needs fixing anyway, so I decided to just take them one by one as they show up.

 

I dissagree with approach of replacing one hose at a time; expansion tank may be easy to replace, but with hoses, it can be more efficient to do them all at once; probability of one hose going bad, while others are in good condition on old car... I would do all of them on between radiator and engine, to be safe. Nothing will guarantee whaterpump will not fail or something else, like heater core, knock on wood (knocking on my head). We are talking about quite old cars here.

 

Agree with the poractive replacment of hoses.
Replaced all the removed hoses when i replaced the radiator
Still trying to find the rubber portion of my 04's heater hoses.
Easy to overlook & forget, seeing as no hoses were were leaking.
Should have some time to spend looking around.
They are available for the 07, wonder if they will fit the 04.
The 04 heater hoses, only come with the metal tubes attached.
Naturally they cost a lot more, anyone know if they are interchangable???

 

I'm going through this right now. I have not found the hose assembly that connects under the expansion tank. Parts diagrams call it a drain hose. It connects to the expansion tank with a spring clip fitting, drops to a tee. On side of the tee connects to the top of the auxiliary coolant pump, and the other leg of the tee connect to one of the heater pipes. I have found all of the other hoses and have them on hand, but that assembly apparently no longer exists. After considerable digging and wrong parts arriving and being sent back, the folks at Harper Jaguar and I decided that the part number is C2C24567, which showed as available on Harper's parts site. I got an email a couple of days later, however, stating that the part is no longer available from the manufacturer and they refunded my purchase. Hopefully the hose is OK, because it's the only "old" hose staying on the car.

I will tell you that the 2004 and 2007 hose fittings on the heater pipes are different. One of my "mistakes" was a 2004 drain hose, which looked the same in the diagrams, but has an incorrect fitting at the heater hose, which is permanently affixed, not just clamped like the one on my hose.

I have on hand all other coolant hoses, including the radiator hoses, the hoses to the auxiliary coolant pump, the throttle body hoses, the hose to the top of the expansion tank, and the EGR hoses. his was a significant expenditure, but as I started my repairs, beginning with a new radiator, i started a chain of failures. The expansion tank cracked. Then the water pump week hole plug actually blew out. That's when I decided to forklift anything that carried pressure.

Stupidly, I've just realized as I type, that I haven't ordered a new thermostat housing, and I need to do that!

 

Just to keep you updated and maybe help others with such strange problems:

After the exchange of the expansion tank to a new OE part (surprisingly affordable for a Jaguar part) the car is now keeping its liquids again for over a week.
That really seems to have been the issue, although I really can't understand how such a cracked tank alone can result in the effects I had before (no coolant loss on long distance, excessive loss at short distances). I'm honestly puzzled

But since I never know what issues the green one has still hidden in his sleeve to throw at me at most inconvenient times, I decided to just be happy for the moment that it's back on the street and does what it's supposed to do, drive and look pretty