Gentle Listers, My 2003 X308 overheats
losing its coolant. Things done to date are: close inspection of the “V” valley to ascertain if there is a leak there as happens more often than it should. There is no leak I can discern from above and below. Removal of the thermostat tower (aluminum) to replace its seals. Replacement of thermostat with new (tested for opening) including the seal. Tightening of all hose clamps including doubling up with screw clamps of the two that have not been replaced. Inspection if the atmospheric tank (located behind the pass. side bumper and above the bottom plastic closing shelf).
In short I simply can not find any leak or reason for overheating. Any ideas will be appreciated and investigated.
If it actually has overheated in the past for some other reason, then it’s very possible the head(s) have warped. This would cause air to slip into coolant (and/or coolant to get into the combustion chambers) causing either flow into the overflow reservoir where it eventually spills out, or consumption as it is burned in the cylinders.
One sign of this is hearing percolation or bubbling sounds in the coolant reservoir. This is a sign of the leakage. I know this because it happened to me when the cheap plastic piping leading into the thermostat housing failed and caused an overheat. It drove OK after repair, but it kept losing coolant.
I had to have the heads pulled and resurfaced to make them flat again (this was back in 2004 so it made sense then to pay for the work.)
I had a constant loss of coolant and had to up every day or so. Turned out it was a pinhole leak in the rubber pipe that connects from the Heater Pump to the back of the block, it was spraying onto the hot manifold and evaporating without any trace! Bstrd to find, cured by splicing in a piece of rubber pipe as the back of block connection is not easily accessable.
Great suggestions so far. I will see about them. Jimbov8 writes the only way to know if there are any leaks is to pressure test the system. Is this something I can do myself with an adaptor and a radiator pressure tester or are you referring to another test - say a cylinder leakdown test?
What you need is a Mityvac MV4560 cooling system pressure tester. When you get one, you will wonder why you never had one before.
Does it overheat in traffic, or at speed?
Has anyone done anything to the hoses from the header tank recently? A common cause of overheating is mixing up the small hose connections to to header tank.
Mind you the point I was making is that a pinhole can cause coolant to disappear without trace.
the point about the header tank hoses is a good one as this has caused problems in past posts.
Gentle listers, I received my Mityvac MV4560 cooling system pressure tester and tried it out on the car. NO JOY. It seems the X308 has two forms of sealing the system in the cap. The Mityvac appropriate cap has only one. In any case it does not ever pump up a little bit.
Update. I removed the header tank to try and pressurize it independently adn that’s when I found that I coud not do so. There was a small, imperceptable crack in the header tank in the back and under the cover when installed. I’ve ordered a new tank and am confident that will solve, at least, one of my problems - for now.
Who Knows. I am cautiously optimistic. Geez, I hate plastic in heat/cool situations and in general under the bonnet of a car.
As others have experienced, my 1999 XJR (X308) would consistently lose coolant and I could not find the leak. Finally, driving one day the “Low Coolant” light illuminated and before I could pull over the temperature gauge pegged full scale. To my later horror I learned what Jaguar had done to the temperature gauge reading!!! Needless to say the engine overheated, dropping the rearmost exhaust valve seats on each head.
The leak was a pin hole where the “V” valley heater hose connects to the water pump outlet. You can’t see the hose for the super charger. The engine valley heat would vaporize the water quickly so tracing the leak was impossible. So, to those who have this setup -supercharged or not - if you hoses are over eight (8) years old – change them all. Hoses are cheap compared to an engine overhaul or replacement.
Back to the Temp Gauge… The stock gauge setup doesn’t show actual engine temperature. The computer sends a centered needle command to the gauge when the coolant temperature is between a certain temperature range. Once the coolant temp rises above that range only then will the computer send a full scale command to the gauge. Usually by that time you have a fried engine ! ! ! Was told by a Factory Rep the reason this was done was to alleviate owner concerns about engine operating temperatures.
There is an after market fix - I believe it called Real Gauge - which is an add-on to allow the gauge to show actual engine coolant temperature. Another $$ well spent to invest in IMHO. Search the JL archives X300 for this if interested.
I think epoxy of any kind would not do in this case for the type and placement of this narrow, almost imperceptible crack. In any case, I’ll wait for the tank to arrive.
As for the hateful ‘valley hoses’ I’ve already changed them once on this car and I hated every moment of it. If someone can tell me how to do it without removing the intake manifold, I and many others would be eternally grateful. Till then it remains one of my most hated repairs. Jaguar could have made the part valley hoses connect to a removable replaceable part (or rerouted them) so the intake manifold would never have to come off to do this job. Not easy, I suppose, but they could have done it - OR - were they looking out for lining the pockets of the dealerships.
Real Gauge is a great item, and inexpensive, as you say, when compared to an engine rebuild. However, it is still expensive to me at the age and stage of this car. The last time it overheated was in heavy traffic and all we could do was look for a place to pull over. I don’t think any sort of gauge would have helped except heighten the anxiety. I do agree that Jaguar should have kept genuine gauges in their cars and not pander to the ‘uniquely unqualified to pilot a car’ folks. Operating temperatures simply do not appear on their radar as do many other things far more important to the nation.
Well, I got the new header tank - cap and level sender included - and installed same. I have been a bit reluctant to take it out for a long drive so will kind of sneak up on it gradually adding longer and longer journeys to see if it behaves.
As an aside, I noticed no spurts or wet spots from anywhere so perhaps the insidious small hidden crack was the culprit.