Car's been sitting on a maintainer for most part of a year. I pulled her out, dead battery , jump her I get P0332 w/ restricted performance. Battery's beyond saving, so new battery installed w/ same codes, I do a hard reset, codes remain I can't even clear them via Torque Pro & dongle.

Now there is a small coolant leak somewhere as I lose a few ounces every few monthes. I was hoping it was just the leak & sitting had fouled the knock sensor to clear after drying etc. This leak's baffled 3 shops via pressure test etc. but is has to be in the KS' vicinity ?!

Guess I'm off to hunting a KS & leak ?!

 

The most common reason for that code is a faulty knock sensor. It is fairly easy to replace.
2000 JAGUAR XJ8 4.0L V8 Knock / Detonation Sensor Connector | RockAuto
The coolant leak is another matter. Is there coolant on the garage floor after reaching oper-
ating temperature? If so, try to trace it to the source.

 

There's never a floor trace it's really baffling. I'm going to thoroughly search around that KS & see what's going on. Thermostat tower has been upgraded to metal years ago so it's not that.

My theory is that the leak is pooling when it sits for extended times & fouling the knock sensor. When the car's being driven often, the sparse leak dries almost instantly so no trace ?!

 

Concerning the coolant leak, there’s two places I’d recommend checking. Start off by removing the air intake tube and the large center panel between the TB and cowl panel. First place to check is on top of the catalytic converter on the passenger side. The quick connect (I know there’s a name for that connector but it escapes me) on the octopus coolant hose where it meets the metal pipe is a common area that can leak coolant and immediately evaporate when it hits the top of the cat. The second place to check is just above the very top of the transmission where it meets the engine is a black plastic one way valve that is part of the octopus hose. Multiple times I have seen these one way valves with a faint crack in them and it leaks out on top of the transmission and can burn off before hitting the ground. Just make sure you have a good strong flashlight and it should be somewhat easy to see if it’s either one of those. You may have to feel around the one way valve for any oily residue. I’ve also resorted to using a mechanics mirror a few times to see if there’s any traces of dried coolant residue under the quick connector.

 

I seem to detect the voice of experience here.

 

Yes I will get out w/ my uber lumens tactical light in mouth,vodka concoction in hand, clad only in boxers,wife beater t-shirt & slides lol. My neighbors love my late night tinkering in our well lit cul-de-sac.

 

I had a similar issue of untraceable coolant leak. I let the car sit for a month and then the knock sensor came on with restricted performance. After inspecting it with a flashlight, I saw coolant forming a puddle around it. I then ordered two new replacement hoses that run under the intake as well as octopus hose and connector. Ordered new intake gaskets as well.

It is a relatively simple job to do. Good luck finding the mystery leak.

 

Update :

Saturated connector in electrical contact cleaner,filled w/ fresh ethanol free fuel after about 4 miles the restricted performance went out. I pulled over, cut off to restart & it resurfaced, but this time it allowed Torque app to clear it. Hasn't came back since, did some spirited freeway driving to ensure everything was dried out & getting air. Will keep an eye on it & concentrate on the coolant leak. Just gotta keep the ole girl more active.

 

This probably won't help, but I had a small, mysterious loss of coolant for several years. Seemed to always be after spirited driving, but it was never obvious enough nor severe enough to tell for sure. I was pretty sure it wasn't a head gasket or other serious problem because it was the same for several years, and I don't think a failing gasket would last that long. A few times I even tried those kits that test for exhaust gas in the coolant. Nothing.

Anyway, there was never a drop of coolant visible under the car. That is, until one day I was changing oil and I noticed a drip on the lower air dam ahead of the left front wheel. As you probably know, there is an overflow coolant container behind the bumper / ahead of the wheel well. The container has an open port hole in it about halfway up the side. Further inspection revealed traces of dried coolant that had originated from that port hole at some point, and this new drip was visible right underneath it. Apparently from time to time it would leak from that hole, but it must have been small enough amounts that would dry before I parked the car, thus no visible drips.

I epoxy'd a small hose barb into that hole and ran a vacuum hose up to the engine compartment and hid it by looping it around something, leaving the end of the hose open so it could still breathe. Idea being that if it was just an occasional slosh that escaped through the port, this would fix it. If it was a more serious problem and too much coolant was being spewed into the overflow, I might see it in the area where I ran the hose. It seems to have fixed it because I haven't added coolant for a long time now and have never seen any coolant near the hose I ran. I make a point to peek at the overflow container whenever I'm under the car for something, and it never has more than an inch or so of coolant in it. At the time, I also re-seated the lid on the overflow container, so maybe it had been oriented in such a way that allowed coolant to spew out of the port hole once in a while.

Just a thought. Something you might look into.

 

Put her back away, this time w/ XL puppy pads underneath, the game is afoot.

 

"when you have eliminated the impossible, whatever remains, however improbable, must be the truth"

 

What if nothing shows up on those pads?

I just thought of 4 other possibilities all related to the expansion tank.

1) I’ve seen the expansion tank leaking on the backside (closest to the firewall) where the seams meet where it’s not very visible to spot a leak.

2) Where the overflow coolant hose meets the expansion tank on the underside of that hose closest to the firewall.

3) The expansion tank cap can fail and prematurely release cooling system pressure into the overflow bottle behind the D/S fog light and since that overflow has about a 11mm (between 1/4” & 1/2” anyways) wide opening, it can easily vent to atmosphere and you’d never detect a leak (or problem).

4) The coolant level sensor on the bottom of the expansion tank... that tube that it sits in I’ve seen a few times gets cracked and have a slow leak also.

A small mechanics mirror and a strong light (after that top center panel is removed) can possibly help you narrow down your search.

If your expansion tank is pretty old (if not the original), it might be time to replace it.

When your car is being regularly driven, do you have to add a few ounces (like you stated in your first post) or when the car is put up for the winter (static) you check and add coolant??

 

Instead of adding more coolant, I might be tempted to check the coolant level cold for a few weeks
and see if it continues to go down. If it doesn't then it is most likely escaping from the overflow and
poses no problem.

 

Back @ it, pulled her out again, same scenario, puppy pads show no trace I'm going to leave the coolant level where it's @(low enough to trigger the light) & monitor it's level. Going to hit the KS w/ contact cleaner & hunt the leak.

 

Is there as UV dye that can be safely added to coolant like we do with R134a to find invisible leaks?

 

Ok I found lots of pooled coolant running length wise along the engine,but none on the ground beneath ?! Any clues as to what in that area is the usual culprit ?. It was sitting for months so I checked before firing up & of course the knock sensor's fouled when I did.

My scenario, sorry for the not so great pic.

Coolant pool represented by red line. US driver's side.






That's a massive leak to not be detected by 3 well known shops ?! I mean I was driving it daily then so maybe it was burning off/evaporating not pooling ?! My hoses to the expansion tank are on correctly & newer so I'm thinking the tank itself is leaking.

 

It may be one of the heater hoses that are on top of the intake manifold.

 

Seems that would've shown during the pressure tests ?! It's pooled both sides of the engine so it's coming from above ?! That's the tank's area is my thinking ?!

 

Sorry, I meant on top of the block, under the manifold.

 

Just going to replace the tank & the rigid plastic lines that connect to it as I'm sure they'll snap during the ordeal. Anyone got the line part #'s on hand ?