Broken oil pump idler


Active Member
Hello all,

Had a wee problem with the 3500s on Sunday! Cruising at 50mph on the way to my daughter's swimming lesson then oil pressure light came on. Not being in a safe place to stop at the side of the road with my kids I had no choice but to swing around and head home - a distance of about 1.5 miles.

I kept revs and load as low as I could, but as expected the top end was rattling as I got home (we live in the edge of the village). I switched it off, jumped into my wife's modern and we made it to the swimming lesson on-time.

Investigating last night found this to be the cause:


Which when removed looked like this:


This had obviously jammed and the end of the dizzy drive was the weak link:


Car continued to run as it uses wasted spark ignition controlled by megasquirt...

Next step is to get the sump off and see how bad it is down there, but I'm not holding my breath! fully expecting bearings and crank to be toast, although having said that the oil didn't show any lumps of metal or glitter when it was drained...If the crank looks ok I'll try new bearings and see what happens.

I'd happily go for another 3.5 if I need to, but there don't seem to be many about on eBay at the mo. Has anyone fitted a later serpentine engine into a P6?


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Ooof! :(
What causes the oil pump gear to crack and fail like that?
Hope you don't find more carnage when you inspect further.
Oh dear, that doesn't look like a whole load of fun. I have a 4L cross bolted engine but it uses an SD1 front cover and oil pump so it just fits the same as the 3.5.

Best of luck stripping it down :)
Thanks everyone, they were fitted a number of years ago as part of the high volume upgrade kit- I can't remember where I got it from, but one of the usual suppliers.

Unfortunately the weather was terrible last night so I didn't get out on the car, but hope to on Friday.
Well, had a poke around this evening and here is what I found.

Only managed to get one main bearing cap off, but although worn, it wasn't scored at all and crank was fine:
Then I had a look at some big end bearings.

Number 3:


Number 7, this had a line but you could *barely* feel it with your nail, and again crank seemed ok:


Number 6:


So now I am not sure what to do! These look waaaaaay better than I thought they would, but obviously aren't perfect either.

I would like to get sight of another main bearing and then go from there, I've chucked the sump on for now to keep dust and grit out of it.

If that looks ok I am tempted to just remove the timing cover, clean the swarf out, fix the oil pump and see what pressure I get...

What would everyone here do based on the photos above?

Many thanks!

I've replaced shells in worse condition than those to help bump up low oil pressure and never had any problems afterwards, so if they all come out in a similar condition I'd just replace them with new.
Check the bearing size, usually marked on the back of the shell if they are not std. The scoring/scratches look like dirty oil at some stage in its life. Get some Plastigauge and check both main and rod clearances.
Thanks chaps, I checked the back and they appear to be standard, I'll get some new bearings on order (and the pump stuff) in the meantime I'll need to remove the timing cover and clean out the swarf from the dead dizzy...
It looks like you are going to get away with it luckily. If however you need a motor I have two 3.5s, one from a P6 and one from an SD1 both running in cars I owned when removed, both available.
Not far from you in Suffolk.
Good luck with it.
Thanks for the kind offer Cobraboy, i'll keep it in mind in case things don't work out! I had looked online for another 3.5 just in case but there don't seem to be many and those that are around haven't been great.

I'll upload some photos later as I am on the train right now and connection is terrible, but I have been chipping away. The stripdown went quickly as it always does (you get that false sense of loads of progress, because put everything back together is the slow bit). the coolant came out a lovely clear blue colour, and I soon had the following done:

-Alternator slackened off, fan belt removed
-Electric fan off
-Radiator out
-Power steering pump removed from bracket
-PS pump mount removed from engine
-Air filter off (with the EFI it limits access to the passenger side spark plugs)
-Crank pulley off
-Plugs out
-Timing cover removed

With that all done the situation was this:

Cam gear looks good, although there are a couple of *tiny* marks on the teeth, which I guess is to be expected

Timing cover did indeed have swarf in it from the destruction of the dizzy drive, which has now been cleaned out.

I have replaced all the big ends, and as per the initial ones I checked they were worn but not destroyed. The tops were all showing some signs of copper. With those fitted the crank can still be turned nicely with a ratchet.

Mains- these were again worn but not destroyed. I did try to change these but inserting the new bearings caused the crank to lock solid. I tried to see if it was a specific one, but it didn't matter which I tried, the result was the same. For now I have put the old bearings back in - getting the tops out and in again was mega fiddly! Luckily I had only attempted the middle three when I realised this, and so saved myself the horror of trying the end ones at all- I simply had to torque those back up again. Ideally I would have investigated further, but lying under the car in the rain and dark deterred me from that idea.

Moving onto the oil pump. I ordered a set of SD1 gears, only to realise when they arrived that these are actually 2mm shorter than the high volume upgrade gears. The spacer plate for the installed upgrade gears is 6.5 mm thick, so the current plan is to make up a new plate of thinner material. I snagged a couple of old dizzies on eBay for £30, so have those ready to drop in.

Timing chain seems mega slack too so I would like to change that, but might put that on hold until I know the thing works ok and gives pressure... Having said that I might do it anyway seeing as it's in pieces in front of me. Indecision rules!

Pics to follow, as I know that's what everyone likes to see.