Ok ive replaced the expansion tank 6 times all cracked within two months i have replaced all hoses clamps thermostat i have no bubbles in tank ay start up no signs of gasket leak so is the a coolant tank tgat works or does jaguar just suck?

 

Perish the thought! I've got over 300,000 miles on my '02 V6. It's been my daily driver for the last ten years with phenomenal reliability. Zero suckage...

Back to your car. Have you pressure tested the reservoir cap? It's supposed to vent pressure at 16 psi, IIRC. If the cap is defective and you keep transferring it to the new reservoirs, that would explain it.

If you don't have a cooling system pressure tester, many parts stores will loan them for free. Or you could just gamble on a new cap.

 

Well 8caps later 6 bleed screws still leaking. Normal exhaust no coolant smell in or out. No overheating. New radiator. Im sure there's too much pressure but i have no other signs of anything my water pump is quiet. Engine oil looks normal not leaking. Its 08 3.0 227000 with 78000 in the last18 months. Honestly its been great except this pesky coolant leak.

 

Okay, after 8 caps, that's not likely to be the problem... And even if you had an engine issue (bad head gasket, for example) that was overpressurizing the cooling system, the cap should have vented to prevent damage to the reservoir.

Where are you getting these reservoirs? OEM or aftermarket?

 

All though i have got the oem used so am i to assume that the oem tanks work best meaning if the oem leaks then its not the tanks? If so i will get one and keep looking. When im done typing im going to check if the cooling fan is coming on properly. I also have an aftermarket fan feom my xtype. Im thinking of using both by putting it on the front of the condenser. Whattau think?i love this car and really hope it makes it to 300,000.

 

From what I have gathered on this forum, there are two grades of tanks:

1) OEM tanks that crack eventually.

2) Aftermarket tanks that crack sooner.


If you have been installing used OEM tanks, most of their service life has already been used up. Given the chance to spend your money, I’d suggest a NEW OEM tank.

I wouldn’t worry about the cooling fan, etc. for now. Remember, even if the cooling system was being over pressurized, the cap should vent that to safe levels. A good tank can safely handle normal system pressure, up to the rated value on the cap.

 

Ok ill get one but i still dont know why the preasure is so high. Every part i replace pushes the leak sonewhere else and back again but always leaking but why? Everything seems to be normal. Or am i over filling? There is no line to match so do i stop at the max lettering or just below or just above but what exactly is just above? Should i be able to read the word max?

 

How about some car details - engine, year, etc...

 

08 3.0 v6 sadan

 

Anyone know if it's safe to run with a loose cap (as with some of the other engines)?

 

Just boiled out. But thats my car.

 

So, you have an over pressure issue in the cooling system. The cracking header tank(s) leaks are a consequence of this over pressure.

What have you done to the cooling system near the start of the changing tanks saga? before or just after the first tank failed.
Changed the DCCV, the thermostat, renewed cooling hoses etc etc?
Check all hose connections are correct, is the thermostat, installed the correct way round, etc etc.

Remember what Einstein said.

 

Upper radiator hose turret blew changed hose then Changed heater core valve then 120 degrees last summer popped radiator swapped it then one by one evwrything else blew replaced everything but the water pump but the heatercore and upper hose replacements were aftermarket so the leak moved around and around like wack a mole and thus here i am.

 

The coolant tank is cracking due to poor molding conditions. Not over pressure of the coolant system.

I suggest getting a new jag unit but from a different source than the others that failed. My reasoning is that you might have gotten them from the same source which means the units in their stock might be from the same batch during mfg.
btw, no customer should have to go through this trouble when buying new OEM parts. But... I've been an OEM engineer for closing in on 30yrs. Trust me.. try to get one from a different molding batch (we call it "lot")

You could try the jag vendor area --> https://www.jaguarforums.com/forum/v...lassifieds-10/

 

In post #5, OP says he's been installing used OEM tanks. I think that would explain a lot. Let's say an original OEM tank, molded under suspect conditions as you've suggested, might only be good for X amount of time in service. Or maybe it's strictly a calendar thing, and the plastic starts to degrade after so many years, even if sitting on a shelf and never installed. Most likely it's a combination of factors.

But either way, forum experience suggests it's not a matter of IF your tank will fail, but WHEN. And if installing a used tank, a good percentage of its life may have already been used up. It's not surprising that a used tank won't last long, especially with latent defects from the factory.

Has the tank design been improved? Or maybe the manufacturing shortcomings have been addressed? I vaguely remember discussion that vendors are now carrying a new and improved reservoir, but am not 100% certain. But if that is true, that's the part you want to be installing.

 

I didn't catch he was using used tanks.

Does anyone have pictures of where these fail?

 

This is not surprising. The plastic bits in the cooling system are known problem areas. They have all aged at the same general rate and so now you've got multiple weak spots, just waiting to fail.

Let's say you've got three pieces that will fail under normal pressure of 16 PSI. However, part A is only good until 10 PSI. Part B will fail at 12 PSI. Part C is the least bad of the three, and will hold on until 14 PSI.

See where I'm going? Keep in mind the pressure doesn't go up to the 16 PSI max on every trip. Depending on ambient temperature, engine load, and other factors, the pressure might only reach 8 psi on most days. (I'm guessing for the numbers) But then something in the equation changes, such as a hot day, and the pressure climbs to 10 PSI.

Part A is the first to go, because that is the maximum pressure this defective part can handle. You fix that, and all seems well until the pressure reaches 12 PSI as you work the engine hard, doing donuts in the 7-11 parking lot. Part B sees 12 PSI and says, "I'm done!" Fix that and once again all seems well until the pressure reaches 14 PSI and Part C has had enough.

While these cascading faults may be aggravating, they are certainly not far-fetched. I would highly suggest using a pressure tester to pump up the cooling system. See if it will hold pressure or it bleeds down. A pressure tester will also expose leaks you may not find any other way. Some small leaks evaporate so quickly while driving that you won't find them unless you can pump up the system to max pressure while cold.

 

For aftermarket tanks, my independent European car mechanic recommends "Meyle"; I have had one on my S-type for over a year with no issues. The tank comes with a new pressure cap.

https://www.autohausaz.com/pn/18840_...SABEgLqqfD_BwE

Uro tanks, however, are to be avoided like the plague... or so I hear anyway.

 

Certainly not exclusive, but I'd allow the most common point is a very small crack under the nipple on the fill neck, where a small hose attaches that goes off to the plastic piece that contains the tank-turret.

 

Turns out i wasnt burping the system properly. Once i did after watching youtube videos it hasnt leaked since. Thx for all help.