Hello all,

I have a really nice x300 which I imported from a trusted individual in the states. After 3 months of joy and caretaking I was driving along and all of a sudden the car started jerking erratically and felt like it was about to die . I pulled over to find the cats glowing red hot and what appeared to be a rather large oil leak coming from the back of the engine. I suspect a blown head gasket as a lot of white residue resides on the oil check stick, but she has not drank any water, no white smoke has been seen and no warning lights appear (some did during the incident itself, but in a panic I did not see which) but I can tell she's lost compression and is not driveable except very short distances (100 meters or so). Any ideas and tips on how to proceed? i'm planning on removing the head when I have time and don't mind doing the ground work myself. Any advice greatly appreciated.

 

Pulling the head is the right thing to do if you have confirmed loss of compression.

From your description you may have a break between a cylinder (or two) and an oil way in the head. That would explain the "rice" (white residue) in the oil and it would explain why you are not losing water.

It is likely that the excess pressure in the crank case (from engine compression leaking in to the oil ways) is forcing oil out of the engine at weak points (for example the valve cover seals at the back of the engine).

Burned out valve could also be a cause, but I think less likely.

If we were talking about a different engine then piston rings would also be a suspect for your symptoms. But the AJ16 engine and it's predecessors are pretty much bomb proof below the head.

 

Thanks a lot, I'll pull the head and shoot some pictures over.

 

I agree with Brendan, the key is to confirm loss of compression before proceeding with whipping off the head. Your symptoms do suggest a possible gasket failure but could be other things too. I'd do some checking first. Here are a few things you can look at, in no particular order.

Plug in an OBD-II scan tool, even if your CEL is not on, if there are any codes set the tool will display them and will give you some clues.
Pull the plugs and look to see if they are oily or have coolant on them.
Use a vacuum/pressure gauge to check the compression on each cylinder.
Plug the gauge in to a vacuum port and run the engine. Look at the readings.
If the gauge floats between say 5 and 20 inches Mercury that could indicate a blown gasket.
If you are reading steadily in the 15-20 inches range and it rhythmically drops by 6-8 inches, that could indicate burnt valves.
Snap the throttle, vacuum should momentarily drop to around zero and then bounce back up to 3-4 inches above normal before settling back down to normal reading. If it doesn't go above normal or barely does, this would indicate worn rings but as Brendan says this is very unlikely with the AJ6/AJ16 engines.
Even though you are not seeing any white smoke from your exhaust, it's worth putting your hand over it to feel the pressure and also smelling it for unusual odors.
You can open the the coolant cap and look to see if any bubbles appear when you rev the engine and/or buy a simple test kit at your local parts store that will test the coolant for any oil or petrol.
Drain the engine oil and look at the colour or for any metal bits or shavings.
You said the cats were glowing red. If they have melted all manner of drivability problems can arise, including loss of power and stalling. The resultant increase in pressure can force oil past seals. You can check the cats by doing a back pressure test.

 

Hi
Keep us posted with what you find... a few pictures would be helpful too
Good Luck
BigBoss in Dallas TX

 

Here's a guide put together by David fieldsend regarding changing the head gasket to use as reference

https://www.jaguarforums.com/forum/a...aguar-x300-pdf

 

Excellent!! Thank you all for the good advice, I'm hoping to get to work on it beginning of next week

For this week I have to get my temporary car through an mot however, good thing I don't mind getting my hands dirty!! Will confirm compression and do a proper backpressure test asap before pulling head off.

Thanks for tips and links, will keep you all updated!!

 

@Allan G, work has had me swamped for a while, so the big cat ended up on the back burner. However, I got around to her last week and did a compression test, no problems and all cylinders within 10% of eachother, did an exhaust compression test and got high readings when I revved her up a bit, ordered a new downpipe cat and replaced it (only downside was that the US model has 4(!!) O2 sensors in the downpipe and the UK ordered replacement only has 2 which instantlt pops a po1185 and po1186, but does not seem to affect driveability. I also re-spliced the wires going to the spark plug hats as a couple had been cracked and split which I suspect caused them to spark againt the block interfering with the constant performance of 1 or more cylinders, thereby sending unburnt fuel through to the cats, sound reasonable?? Anyway, she now drives great, aside from the fault codes. P.s. when I hooked up my obd2 prior to this procedure, no fault codes had been logged, a bit disconcerting. Allan, I owe you a huge debt of gratitude, as I would have disassembled the entire engine had it not been for your advice, live and learn I suppose, many thanks!!!