Hi all,

Looking for a bit of advice on my '97 XK8. I posted a while back about oil ending up in the airbox, and since then I took it to a Jag specialist (JagTech in Stockton-on-Tees). He reckons it's down to excessive backpressure caused by failing Nikasil liners.

I do trust his opinion, he used to work for Jaguar when they were doing engine replacements for this exact issue — but I've read up on Nikasil failure and it seems like it usually comes with other symptoms too (like rough idle, poor starting, etc). My car’s running fine otherwise — it just keeps pushing oil into the airbox and dripping onto the floor eventually. I'd previously written off excessive backpressure as I'd taken off the oil cap and full load breather and there didn't seem to be any excessive pressure, however the bloke told me you need to take the part load breather off, which he then said you could see the oil chugging out. It also doesn't seem to be burning oil, I've not witnessed any smoke from the exhausts on start up, or when accelerating. I would have thought that excessive backpressure would cause the oil to be forced back into the engine when loaded, rather than just on over-run?

Just wondering — could it still be something else causing the backpressure? Or is it possible for Nikasil failure to only show up like this without the usual other problems?

Frustrating one this, especially as it's a low mileage car and feels solid apart from this issue.

Advice and opinions welcomed

Jacob.

 

Was a compression or leak down test done?
l would certainly be checking the breather system thoroughly before affixing blame on the nikasil.

 

I agree about the breather system. The odds of this being a Nikasil problem are next to zero, unless it has been like this for the last 20 years and you've only just noticed.

 

Hi both,

Thanks for your responses. I don't think the bloke undertook any test as such, he just told me when taken off the breathers it was chugging oil out. I'll email the garage and double check.

I've only owned the car for 2 months so not sure if the previous owner had many issues, but he didn't seem to think so.

Looking at the past MOT history, since 2005 it's only done 17k miles, and I believe they'd don't enjoy not being used.

I have taken off both breathers, the full load breather is new and that all seems to be fine, the part load breather I've taken off and inserted a wire into the hole to ensure it's not blocked and that seemed okay. I'm wondering if it's worth replacing the part load breather pipe, to see if that's the problem? I've taken it off at the engine end and blown down it to ensure it's not blocked, but it could maybe have a split somewhere on it, would that cause issues?

Jacob.

 

As said above, I would start with a compression test. If the cylinder are all around 150psi, then all is good within the cylinders. If it's low, then do the usual oiled cylinder compression test. If it increases, then, for whatever reason, the bores are worn.

Richard

 

+1 on the compression test, or - better still - a cylinder leakdown test, e.g:
https://ricksfreeautorepairadvice.co...leakdown-test/

My understanding is that the nikasil engine compression figures will show low until the motor gets up to temp.

 

Have you checked/replaced the PCV valve?

 

There is no PCV valve on the 1997 X100 engine but two separate crankcase breathers. The OP has checked and cleaned both of these.

Richard

 

I have a 97 with the original nikasil motor still in it. I had oil in my airbox as well. I cleaned the breather as per the sticky in this forum but it wasn’t clogged. When I took off the valve covers to do the timing chains and tensioners I noticed there is a baffle molded into the covers with what looked like steel wool in it to keep oil from blowing through the breather vent. Well my baffle was cracked allowing oil to get through where it shouldn’t, likely causing my problem. Could be the source of your issue as well.