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Excellent commentary, as usual guys! I have been paying attention because I get an occasional whiff of coolant after a drive, and so far I haven't located it. It may well be in the areas under discussion.
Secondly, would someone please supply information on the alumin(i)um T'stat replacement? Shortly after I bought the car in 2017, I replaced the seeping plastic T'stat housing with like and kind plastic. So far so good, but the design - or rather, the method of manufacturing - is obviously failure prone.
I was aware that metal housings had been used by Jag previously, but all the images showed a completely different hose configuration. I did search the Internet but found nothing suitable, advertised for the later XK8s, so I decided to leave well enough alone and go with direct replacement.
There is no aftermarket aluminum thermostat housing available for the 4.2 engine cars (2003 to 2006). It is only available for the 4.0 engine cars (2002 and older)....
I have been paying attention because I get an occasional whiff of coolant after a drive, and so far I haven't located it. It may well be in the areas under discussion.
On my '97 I had a similar thing, whiff of coolant after a drive that I couldn't find. Coolant would also slowly disappear from my reservoir, mm by mm.
I believe it was worse in winter when I'd be running the heater, but I didn't keep enough records to say that for sure.
Eventually I found a tiny leak in a tee right behind the throttle body. One branch was a norma connector and the other branch was one of those standard constant tension bands. After driving the car, if you let it sit idling and stare at the location, it will cycle between a trickle of coolant wetting the area before drying out and back again over the course of maybe ten minutes. I had to happen to catch it during one of its wet moments. I believe it was the band and not the norma leaking.
No idea if the plumbing is the same for newer cars, but yeah, the intermittent wetting made it challenging to find.
Small leaks on either side of the octopus can be difficult to spot as the connectors both sit above a cat, so any drips are vapourised immediately. There's an O-ring involved with each joint that some have successfully replaced, but the big Norma on the RHS is likely to fall to bits on disassembly if the octopus is of any age.
The coolant expansion tank is also sat more or less over the LHS cat, so a leak there is another possibility. The tee arrangement on the LHS is the same on later cars.
I checked the backflow preventer valve on the spider/octopus hose & the aux heater hose to the heater core & they are the same. I haven't checked if the part is available by itself but you can read the number off the images and search for it.
All, I have a 2002 XK8 with a similar smell of cheap pancake syrup (ethylene glycol) everytime I turn it off. The previous owner complained of it also, said his mechanic couldn't figure it out. You guys have inspired me to dig into this and get it knocked out.
I found on mine AFTER I replaced the Spider/Octopus hose (which was leaking at the Norma coupling) that the Expansion tank was leaking from the level sensor at the bottom rear of the tank. A pressure test of the system cold didn't reveal this leak. After a quick drive around the block to get the engine up to temperature I'd shut it off and open the hood and listen to it "sigh". The coolant leaks out of the level sensor onto the exhaust and vaporizes with a sighing sound. I thought the car was crying. Maybe it was. I could also see a small puff of white smoke rising from the engine bay at the rear on the driver's side (US spec car). The coolant smell was also VERY obvious.
The expansion tank is one possibility. The Spider/Octopus hose under the trans tunnel is another. The Aux heater hose from the pump to the heater core is yet another possibility. These are spots that you MAY not see any signs of coolant puddling under the car. They vaporize as soon as the drips reach the exhaust. The distribution pipe is another popular spot for leaks. If you have the plastic thermostat housing it's also a popular spot. Last obvious spot is the water pump.
The best way to diagnose it is to get a coolant pressure tester from the auto parts store (where they "loan" the tools) but you'll need an adapter which the parts store won't "loan". You'll have to purchase an adapter. There's one from Stant (I don't remember the part number) or there's one on Rock Auto from a different manufacturer. They'll both fit the tool the auto parts stores "loan". Both adapters are about $40.
I checked the backflow preventer valve on the spider/octopus hose & the aux heater hose to the heater core & they are the same. I haven't checked if the part is available by itself but you can read the number off the images and search for it.
I found on mine AFTER I replaced the Spider/Octopus hose (which was leaking at the Norma coupling) that the Expansion tank was leaking from the level sensor at the bottom rear of the tank. A pressure test of the system cold didn't reveal this leak. After a quick drive around the block to get the engine up to temperature I'd shut it off and open the hood and listen to it "sigh". The coolant leaks out of the level sensor onto the exhaust and vaporizes with a sighing sound. I thought the car was crying. Maybe it was. I could also see a small puff of white smoke rising from the engine bay at the rear on the driver's side (US spec car). The coolant smell was also VERY obvious.
The expansion tank is one possibility. The Spider/Octopus hose under the trans tunnel is another. The Aux heater hose from the pump to the heater core is yet another possibility. These are spots that you MAY not see any signs of coolant puddling under the car. They vaporize as soon as the drips reach the exhaust. The distribution pipe is another popular spot for leaks. If you have the plastic thermostat housing it's also a popular spot. Last obvious spot is the water pump.
The best way to diagnose it is to get a coolant pressure tester from the auto parts store (where they "loan" the tools) but you'll need an adapter which the parts store won't "loan". You'll have to purchase an adapter. There's one from Stant (I don't remember the part number) or there's one on Rock Auto from a different manufacturer. They'll both fit the tool the auto parts stores "loan". Both adapters are about $40.
Happy diagnosing.
Had same problem with leak from expansion tank. Most evident after driving and then shutting off engine, coolant would drip on exhaust. Replaced expansion tank and no more coolant leak.
Wanted to close out my side of this thread. One-Way valve replaced thanks to RJ's kind assistance with a part donation.
Part# MJA6732CA still available at Terry's Jag (today is July 2021).
Same 1 way valve used elsewhere in the heater hoses.
In a jam? Need to temp it? The valve is 3/4 inch outside diameter. Pick up a 3 inch pipe from local plumbing store.
Hose clamp Notes: you will have to open (IOW squeeze the tabs together ALL the WAY!) the clamp as much as possible to get it back over the hose! I got them off with a hose clamp tool, but given (a) the working space; (b) the need to open the clamp 100%; i found it was much easier to use lock jaw pliers to reassemble.
The coolant flows starboard to port. There is an arrow on the valve. Odds you'll see the arrow before removal? About zero . . . :-)
Now, you're thinking: what? A job by John without a don't do what I did / lesson learned comment?
Well folks, let's just say you have no idea how scary she can idle and how crappy she drives if you maybe put the throttle cable back on too tight. (Yes, an Einstein move, don't ask).
You'll be thinking: how many vacuum connections did I break, fishing around back in there? Maybe all those posts saying: ah, ignore the TSB warning were mistaken. Its OK to clean the butterfly valve area if it has the "sticker" on the throttlebody. Then you look at the price of a new throttle body. . . Stomach drops - Uh oh.
BUT GOOD News. A simple readjust of the throttle cable tension, no slack no pull, and she drives like a dream!
