My BMW's also use VVT, similar to what's on the jag engines, with similar solenoids.

On that car, they have a pair of very small oil filter units on the side of the engine, in place in the oil passages that feed the VVT, to prevent contaminants from fouling the VVT solenoids.These can be removed and cleaned when needed.

I'm going to pull my XK150 4.2 N/A VVT's and clean them but can't find any indication in the manuals for a similar small filter.

Anyone know if there is one separate from each VVT, or is on the oil filtering part of the VVT solenoid itself? Or simply ignored in the design? [question answered below --panthera]

Thanks!

Panthera

 

I'm sure you are correct about the lack of additional filtering specifically for the VVT's and it was this design flaw that made JLR so pedantic about oil specification. Remember the early days of the dedicated grade of Castrol with a chemical tracer and warnings that warranty claims would be rejected if the 'wrong' oil was found in the engine.

It's avoidance of VVT issues that encourages me to make more frequent oil and filter changes than recommended rather than concerns about bore or bearing wear.

Graham

 

@GGG , reassuring to know I’m not the only one.

Many speak of “extended drain intervals” and “sealed for life”. I’m not subscribing to that.

 

Good points, thanks Graham.

EDIT and CORRECTION: I reviewed the parts blowup and found that there is a filter for this unit. It's part of the Module Carrier, is PN AJ18264, and is < $10. Of course, since it's in the module carrier, the valve cover will have to come off to install it.


I was examining some engine data the other day and saw that I was getting very occasional misfires on one side. Since I was getting misfires on one side, this seems a commonality.

Note there were no codes. I was just digging into diagnostic data and saw the random misfires.

Caused me to want to dig into the VVT on my XK150, to see if I could easily clean it. First Learnings (see pic):

• VVT on my engine requires valve covers be removed. On other cars, the VVTs can be removed from the engine with a single bolt.
• I looked at online replacement to see how they were built. There is a replaceable screen on the internal module carrier, under the valve cover.
• The two items above still lead me to agree with Graham that more frequent oil changes are better, since keeping the VVT clean is important to valve timing.
• Guidance: If you're pulling the valve cover, to clean the VVT solenoid, replace the filter.

Fix? Change oil regularly to avoid varnish coating (and other crud) on the VVT's. I usually change mine annually, since I only put on 3-4Kmi per year. Maybe (open to debate) use something like Liquimoly engine flush when changing oil even if oil has been changed regularly in the past. If really necessary, grit my teeth and open the valve cover to clean the VVT's if I suspect varnish coating or get VVT codes.

Second learnings:

• My VVT connectors were covered in oil. This is due to typical shrinkage on the VVT-to-Valvecover gaskets.
• I opened the connectors and flushed them with MAF cleaner (other contact cleaners would work as well), reconnected them.
• See pic. The left side connector has the open end of the plug facing forward. This forced seeping oil into the plug from air movement. The other side was cleaner, because the plug faces backwards, but still had oil in it.

Fix? Replace the VVT gaskets to prevent further seepage. Easy fix, gasket available for $5 each, takes 5 min each. See Below. Note this is N/A 4.2 engine. Did not examine SC or 5.0 engine.

Poor VVT management can cause misfires, according to the 4.2 engine manual. My engine was a bit rough on idle, and it seems to smooth out a bit after cleaning the oil out of the connectors.

ALSO: you can test your VVT's in place:

• Remove connector. Use an ohmmeter to test resistance. Should be somewhere around 8 ohms.
• A couple of leads and a nine-volt battery can be used to trigger the VVT. You should hear a click when the battery leads are connected to the wires.
• That said, these are pretty simple, solid units -- they likely will not electrically fail. More likely is performance degradation from gum and varnish buildup in the unit. Or in my case, with oil flooding the connectors.

Hope this helps. Why Jag, unlike most other engine builders, chose to lock VVT solenoid and filter access beneath the valve covers, is a mystery.