Hello guys;

I'm scratching my head a bit on this one.

For the last few months, my oil pressure is occassionally slow to come up at engine start. Until today, it's happened about 1 in 20 engine starts, and after about 10 seconds the pressure comes up to normal. The pressure sensor is NOT the problem, because I can hear the change in engine noise when the pressure finally comes up.

Once the pressure comes up after engine start, it stays up. No dips or weirdness while driving...the problem (so far) only occurs at engine start (and until today, about 1 start in 20).

It can happen on the 1st start of the day, or the 10th. Warm weather or cold. Oil level is fine, oil changed 2,000 miles ago. Mobil 1 5W-30.

Today, twice, the pressure has taken MUCH longer to come up on two separate starts. It's been a bit scary. The engine starts knocking a bit, it gets a bit louder, I panic and shut the engine off. Then when I restart 30 seconds later, the pressure goes right up to normal.

What's up? Please note that I changed my tensioners a few months ago, and found a LOT of plastic in the oil pan and oil pick-up screen. I cleaned it all out, so theoretically I should be good there.

If the oil pump is going bad, why would the problem only appear at random start-ups, and the pressure NEVER dips once it comes up to normal?

Any ideas? Thanks very much for all of the wisdom about to come my way!

 

Do a search on "low oil pressure" in the forum. We just had a lengthy discussion with another gentleman with a similar issue. His pump "lost prime" and was having weird issues. Could be a weak pump, clogged screen, sticking pressure release valve/spring in the pump... etc. In his case he had a broken (plastic!) oil pick-up tube on the pump. Unfortunately, or fortunately, depending how you look at it, he got it resolved, but had to drop the pan and replace the pump. Look for that thread-- I think it was an XJ-6. Mark

 

Mark-

I did see that thread, but given what I know about my particular case, none of it seemed to apply. He had just changed his oil (I haven't), and you're right - his plastic pick-up pipe was broken (mine isn't broken, or clogged).

Most of the other threads I see on oil pressure are 1) happening right after an oil change, or 2) happening while driving. Neither apply in my case, which is why I'm a bit stumped.

 

Have you tried to change the oil filter?...maybe your has an intermittently functioning oil retention valve.

 

Haven't tried that, but I've been using the high quality NAPA GOLD Wix filters. Would that problem only show itself at startup?

 

Yes-- that is a good point. Could be a collapsing or faulty filter too. Easy to swap that out!

 

How many miles on the engine? Do you know the maintenance history?

 

114,000 miles on the car and engine, which runs very smoothly other than this issue.

I've owned the car since last summer, and have 80% of the maintenance history in-hand. It's been well-maintained in general, although there's a bit of sludge in there I'm hoping to clean out with regular changes.

 

Two more ideas:

1. sticking oil pressure relief valve. (used to be a separate component on earlier Jaguar engines but it's built into the oil pump on the AJV8)

2. faulty diverter valve to the oil cooler.

Graham

 

Thanks Graham-

No oil cooler on my car, but I'll do some research on the pressure relief valve. I really hope I don't have to replace the pump...that's a big job.

 

Yes

 

Sounds like an ideal time to do an engine flush (to remove any sludge, and maybe free a sticking release valve). Put on a fresh filter and new oil. If it continues, I would personally bet on a oil pump/screen issue... MC

 

I have a similar issue that only occurs on very cold starts. Never any other time. Full synthetic 10w30 with 66k miles. Never heard any issues with the engine such as VVT chatter or other knocking but it takes 10 to 30 seconds for the gauge to come up. With carefully listening for engine noises I just grit my teeth and wait.

Permanent pucker in the driver seat now.