Hi all.

I’m the proud owner of a new (well… 2001) XKR coupe. I’ll post up on the introductions page once I’ve got some nice photos to share.

I’d like to thank everyone who contributes to this board for the invaluable information that you all provide to people like myself looking to buy and maintain one of these little beauties.

So.. to add my initial learnings to the mix, when I picked up my jag, she had been stored for a couple of years and was a none runner… I have dealt with the following codes and issues:

P0121 – TPS sensor error - Figured I was up for a new throttle body for this, especially after watching the episode of Wheeler Dealers where they flipped an old XK8. However, removing the TPS plug at the throttle body, I discovered that someone had snapped off the retaining lug on the socket, so the plug could work loose.

Sprayed everything with contact cleaner and seated it firmly with a tie wrap and the code hasn’t returned in 2 months and 1,500 miles… so fingers crossed.

P1638 and P1642 (CANBUS/IP codes) – Putting in a new proper spec battery solved this instantly.

P0171 and P0174 (lean mixture) codes – LT fuel trims on both banks were +19.53 on idle and +5 on freeway cruise throttle of 2,500rpm, tripping a performance restriction mode every couple of days so… likely a common air leak somewhere.

I built myself a homemade smoke tester out of an old coffee tin, a cigar, a rubber glove, 12v air mattress pump and some rubber tubing (quite proud of that, I am…) and traced a leak to the intercooler inlet ducts. Replaced those (and two of the plenum bolts that snapped on removal and had to be drilled out) and the LT trims (both banks) are now settled at +8 on idle… and flicking around +/- 2 to 5 on level freeway at 70mph, so low enough to not trip an RP condition, but still some work to do.

P0400 – EGR flow code… This only popped up after I’d replaced the intercooler ducts… so I may have knocked the EGR valve or piping so that’s my next job to tackle, but that may also be causing the elevated trims as well I think. We’ll see this weekend.

Hope that all of those learnings help someone else down the track, but now… on to the really interesting challenge.… and a pop quiz.

Here is a picture of my engine bay… Ignore the tape measure sat on the intercoolers… I was trying to see if she’d fit through my garage doors or not. The hosing is what you need to be looking at - really closely!!!



My car had annoyingly hot intercoolers, as in too hot to touch once the engine had warmed up. She also has an LPG kit installed… Now, without segwaying into the pros and cons of LPG conversions on these cars… Can anyone have a stab at why my intercoolers are running so hot?

 

The Intercooler Circulating Pump (located below the air filter housing) may not be working. You can hear it when you turn the key on before starting the car.

 

agreed. also the coolant may topping up from the intercooler fill plug. I just drained and flushed my system using the JTIS procedure and can't believe how much cooler the intercoolers are running.

 

Thanks Paul and keeyszig.. I checked the Intercooler pump… seems to be running fine and I could feel water flowing through the lines.

Good ideas though. That’s why I love this forum!

Likewise, the coolant in the intercooler loop was topped up last week, although now that you mention it… topping it off was a pig, and I seem to recall spending hours (literally) with constant gurgling and bubbling and level fluctuations going on.

I think though that I might have found a rather unique problem… and hopefully the solution, after a day of trawling through JTIS, pictures of other XKR’s and various coolant diagrams.. Anyway, here’s what I’ve found for future reference – it’s a bit long… sorry :

Quick primer. LPG systems need to be heated, that is to say that the vapouriser, that converts the liquid LPG from the LPG tank into a gas ready for injection into the engine… needs to be kept warm to avoid it freezing up as it expands the LPG into a gaseous state (something about combined gas laws). This is done by taking a feed line from the engine coolant loop and feeding hot water through the vapouriser, then back into the main coolant loop!

Now… my XKR has two vapourisers (kme sgi reducer ac ag necam stag europagas prins landi magic) which are buried away behind the rhs headlight, next to the security sounder. A pretty clever bit of shoe horning was needed to get them in there… but there’s not much space elsewhere in the engine bay I suppose. Each vapouriser feeds 1 bank of the engine with lpg!

So, when I looked closely, there were four rubber hoses routed between the engine bay and the vapourisers in the wing, two gaseous lpg outlet lines that run from the vapourisers into the engine bay and feed the bank 1 and bank 2 LPG injector blocks, and two coolant (or heater) hoses (which you can “just” see in the picture) one feeding warm water from the coolant loop to the vapourisers, and one feeding it back from the vapourisers back into the coolant loop.

That all made sense to me… However, XKR’s have two coolant loops, one main engine loop, and a second loop for the intercoolers, and from what I c an see, they are only connected by a small overpressure bleed/vent line so that they can share a common expansion tank. The vent line between the two is buried away near the ABS block. As I understand it, despite the vent line, they are effectively separate coolant loops and there is no cross feed between the two. Certainly their coolant runs at very different temperatures!

So… what some clever chappie has done with my car, presumably when installing the LPG coolant circuit (and you can “just” see it from the picture in my earlier post) is this:

They’ve taken the intercooler return line (that goes from the intercoolers, down to the intercooler pump and radiator… and popped a grey t-piece in there then taken a line out to the vapourisers. They’ve then fed the coolant return line, from the vapourisers, back up into the engine bay… but they haven’t connected it to the intercooler loop at all, they’ve spliced a metal y-connector into the air bleed line that goes from the back of the thermostat housing block and runs through to the expansion tank. (In the photo, you can just see the y-connector behind the wrist strap for the tape measure.)

If you know XKR’s you can also see that the expansion feed line going to the expansion tank from the thermostat housing is much thicker than normal, at least thicker than any other XKR engine bay photo that I’ve seen – I am new to Jags though so I could be wrong.

So… what does this mean? Well, I stand ready to be corrected, but I think that what they’ve done is to bridge the two coolant circuits!

Feeding warmish water out of the intercooler loop, through the vapourisers and then back into the shared expansion tank, and hence into the main coolant circuit. This means that there would be a negative pressure in the intercooler coolant circuit, because its coolant is being drawn into the main coolant loop via the expansion tank, and this negative pressure can only be relieved by…. pulling (95 deg Celcius) hot water across the vent line from the main coolant circuit, back into the intercooler circuit. Hence the intercoolers being very hot to touch even when the engine is just idling as the intercooler coolant being pumped to the expansion tank would constantly be replenished with hot water from the main coolant circuit.

This could also be why I had such trouble topping off the system last month as it kept pulling coolant from the main loop causing level fluctuations and gurgling.

Effectively… my intercoolers had become “inter heaters” and were furiously heating the inlet air! Maybe you could argue a positive benefit that they functioned as ancillary radiators for the main coolant circuit!? I’ve certainly not had any problems with overheating in the last two months!

So, as a quick fix, I’ve disconnected the LPG coolant lines and isolated/turned off the LPG system, putting the coolant lines back to a stock configuration, albeit with a slightly thicker feed line from the thermostat housing back to the expansion tank and found that the intercoolers now run nice and cool during a drive.

The coolant hoses probably all need to be replaced soon I’d imagine, as there is a bit of bulging in some of them, but I’d still like to get the LPG system working first as from the two tanks of LPG that I put through her last month, without a hiccup, I calculated that she was returning 37MPG, which is phenomenal for a 4 litre v8, and the fuel savings will pay for a lot of little preventative maintenance jobs over the winter.

Jack.

 

The intercooler started getting hot enough to fry eggs on. My car only had 14K miles on it but was 11 years old and never had a coolant change. When pulled the plug on top of the intercooler, I found out why. The Orange oat coolant had Jelled and that always starts at the top point of the system according to my mechanic that worked on jags for 11 years.


It was easily solved by sucking what I could out with a fluid pump from the top and then draining and back flushing the entire system. It takes a good long afternoon with refill (see JITIS) and doesn't cost much. The car performed better with the pedal down afterwards with the intercooler doing it's job. Luckily I did not experience engine overheat.