Oil Pressure Problems

[Boost All The Dollys]

Hi all

I know this question is about a Ford/Jaguar engine but it’s in a Dolomite so maybe an exemption can be made?

After my recent experience of destroying 2 sets of con rod bearings, I think I’ve partially worked out what the problem is but I don’t understand the full picture so I’m hoping some of you old school engine builders can help shed some light on it for me.

So, I’ve fitted an oil pressure gauge and an oil temp sensor to see what the oil is doing while I’m driving. On cold starts, oil pressure is around 50psi while the engine is idling but as it warms up, the pressure drops to around 15-20psi. I have heard this can be normal as thinner oil is less viscous.

My problem is, is that it gauge reading barely changes apart from the cold-hot difference; Idle is 15-20psi, 2000rpm is 15-20psi, 4000rpm is 15-20psi. Currently, I only drive it at below 45/5000rpm as I believe that’s what took out one set of the rod bearings. This is hugely annoying as my current gearing, 70mph in 5th gear is 4000rpm, and I have an extra 3000rpm before redline which I can’t use.

Any advice? I’m leaning towards a restriction in the oil lines or something like that.


Thank you

[cliftyhanger]

Have you measured the crank journals (all of them) for size/roundness?
Checked the oil pump is within tolerance?
PRV?

First set of bearings you fitted I wouod assume you would have checked all this stuff?

[Boost All The Dollys]

Have you measured the crank journals (all of them) for size/roundness?
Checked the oil pump is within tolerance?
PRV?

First set of bearings you fitted I wouod assume you would have checked all this stuff?

First set destroyed the engine so fitted a new one and experienced the same issue, but I’d caught it a lot sooner. I haven’t measured the bearing surfaces but seeing as I got both engines from running cars where the only difference between running in it’s original car and running in this car is that I fitted a remote oil filter housing and an oil cooler compared to the original oil-coolant heat exchanger.

[cliftyhanger]

Bypass the oil cooler as a test?
It would seem your modifictions are to blame, rather than the engines.

[Boost All The Dollys]

Bypass the oil cooler as a test?
It would seem your modifictions are to blame, rather than the engines.

I only fitted the oil cooler recently. before I did, it still did the same thing. But then again, I haven’t noticed a significant drop in oil temps. I know the original oil-coolant heat exchanger was small but with the specify heat capacity of water being so much higher than air, maybe that’s what I’ll have to do to bring the temps down

[SprintV8]

First question is what oil brand and grade are you using and filter.

I know from previous experience these engine’s are fussy about using the correct oil.

Going by your readings they should be higher.
Working on a ratio of 10psi per 1000rpm.
(what we used on are race engines)
Restrictions quite possibly.
Can you drop the sump and check the oil strainer.
Just been thru your posts your not using the original sump.
What’s the oil capacity same or more please not less.
Check strainer to sump for clearance.
Can you fit the original cooler to test.

[Carledo]

I can think of one or two things!
1) what is the OE oil pressure supposed to be? It seems ridiculously low, but is it? The old Rover V8 has a low pressure/high flow system that never exceeds 30 psi cold at revs and can read down to 15psi running at revs hot without there being anything wrong.

2) OIL, are you sure you are using the correct grade, differences are crucial! I put 5/30 in the Carledo once, instead of the correct 10/40 and thought the engine was falling out as the oil pressure dropped dramatically once it got warmed up. Then I looked again at the can and realized my mistake!

3) I think you'd have to be the unluckiest man on earth to have 2 (or is it 3?) engines all with the same problem, unless you've engineered it in yourself with your own mods. So have you modified the sump or oil pickup pipe or even the dipstick in your quest for something that will fit a Dolomite shell. If the pickup is too high or the oil pan too small or the dipstick too short, you may have created a problem. It also occurs that the pressure might be OK but a surge problem from a mislocated oil pickup or similar is uncovering the oil pickup under acceleration or cornering and starving the bearings of oil.

Just a few thoughts, Steve

OH, and one more! I've had 2 brand new genuine Smiths oil pressure guages in a row recently, that consistently under read by about 30%. Are you sure your guage is accurate? Electric sensors are even more prone to failure. When I swapped the instruments about on the Carledo, it has a 0-5 bar VDO switch but I happened to have a 0-10 bar guage and tried it. It then read 10 bar of oil pressure rather than the 5 it actually has. Fitting a correct 0-5 bar guage fixed it. but if i'd done it the other way round with a 5 bar guage and a 10 bar switch, it'd have halved my apparent oil pressure at a stroke (and probably given ME a stroke!)

[Boost All The Dollys]

First question is what oil brand and grade are you using and filter.

I know from previous experience these engine’s are fussy about using the correct oil.

Going by your readings they should be higher.
Working on a ratio of 10psi per 1000rpm.
(what we used on are race engines)
Restrictions quite possibly.
Can you drop the sump and check the oil strainer.
Just been thru your posts your not using the original sump.
What’s the oil capacity same or more please not less.
Check strainer to sump for clearance.
Can you fit the original cooler to test.

To be honest, oil brand has been cheap shite as I’ve had a persistent oil leak at the sump gasket and didn’t want to spend a fortune on good oil for it to leak out. Grade wise, I’m using a slightly thicker oil than most would for this engine but nothing out of spec. I found a detailed engine manual online which had what oil grades to use for different temperatures and used one of the thicker ones.

Most people say 5w30 for it but after I ruined the first engine, I’ve been using 10w40 in the hopes that the thicker oil will help my bearings live. I also have an issue with the oil draining from the oil lines through the bearings when the cars been sat for a bit so the thicker oil is to help the bearings stay oiled while the circuit primes (I don’t start the engine until it builds oil pressure but this can take up to 8 seconds of cranking).

Checked the strainer, no clogs or anything.

Well, sort of. I’d say my sump is approx same size but I will double check that. I’ll check what the old sump actually holds and compare it to mine as the old sump is an odd shape so can’t easily calculate it. The spec says that it should need 5.7 litres and my sump will hold about 4.5 before the level is above the top of the sump (there is more space but my engine is slightly angled back so it’s 4.5L at that angle). I’ve not long pulled the sump off to sort the gasket leak out and it drained out around 4.5L, which didn’t include the oil in the cooler and filter so there should be around 5L total oil.

Can’t fit original cooler as it’s integrated into the engine mount and would be inside the chassis rail. Just thinking about it, although the old cooler is a lot smaller, it would be massively more efficient than a regular air-based one just due to using water and not air.

Strainer clearance was a thought and I’ve just modified my spare one to sit lower in the sump. Original height was approx 120mm from base of engine, modified one is around 145mm, sump height is around 155mm.

With the new sump fitted, it might be worth me redoing the engine mounts to level the engine off. I mounted the engine with the old sump which basically sat on the steering rack and the new sump has a lot more clearance around there so I could lower it down a touch. This would make the sump and the exhaust manifolds stick out from below the subframe, not exactly ideal.

I can think of one or two things!
1) what is the OE oil pressure supposed to be?…

2) OIL, are you sure you are using the correct grade?…

3) I think you'd have to be the unluckiest man on earth to have 2 (or is it 3?) engines all with the same problem, unless you've engineered it in yourself with your own mods. So have you modified the sump or oil pickup pipe or even the dipstick in your quest for something that will fit a Dolomite shell.

OH, and one more! I've had 2 brand new genuine Smiths oil pressure guages in a row recently, that consistently under read by about 30%. Are you sure your guage is accurate?

1) I have no clue. My assumption is that it should be around 40-50psi but Sod’s Law, it could be 15-20psi. Can’t find much online on what it should be.

2) as above, sort of. Not the most common oil grade but one that is specified by the OE as ok. I went from 5w30 to 10w40, just a touch thicker than standard. I’ve just re-read the grade table and I might try some other ones, 10w40 is specced for high outside temps, looks like either 5w40 or 0w30 might be a better option.

3) 2 engines. First one was ruined, second one had spun but not very long or hard by the looks of it. No heat had gotten into the crank or rod and no marks on the bearing surface. I think it spun at the end of a drive I had done the day before when it had broken down due to a bad electrical connection. That fault might have just saved the engine(!).

4) I do understand that smiths gauges might not be the most accurate but it seems quite reliable ie it reads the same under the same conditions. My concern is the fact that it doesn’t seem to increase with rpm. When I blip the throttle, the oil pressure does go up but only when the rpm starts to fall, like water hammer. Oil is flowing fast and briefly there’s more flow in than out. My other concern is that the gauge connection point isn’t the most ideal; on the outside of a bend on the oil filter housing, between the oil pump and the oil filter. This could just be reading the pressure to overcome the filter.

Either way, thank you for the advice. The more I think about it, the more it’s sounding like an oil surge issue rather than oil pressure/flow problem. It’s clearly getting enough pressure to run up to 5000rpm, but when driving at sustained high rpm, oil is returning to the sump quick enough and the strainer is maybe picking up some aerated oil. I’m going to go and have a think about it all and see what I can do.

[SprintV8]

To be honest, oil brand has been cheap shite as I’ve had a persistent oil leak at the sump gasket and didn’t want to spend a fortune on good oil for it to leak out. Grade wise, I’m using a slightly thicker oil than most would for this engine but nothing out of spec. I found a detailed engine manual online which had what oil grades to use for different temperatures and used one of the thicker ones.

Never good to use cheap oil.
What where you using.

Most people say 5w30 for it but after I ruined the first engine, I’ve been using 10w40 in the hopes that the thicker oil will help my bearings live. I also have an issue with the oil draining from the oil lines through the bearings when the cars been sat for a bit so the thicker oil is to help the bearings stay oiled while the circuit primes (I don’t start the engine until it builds oil pressure but this can take up to 8 seconds of cranking).

Again what oil filter are you using,
Some have anti drain valves to help stop draining back.

Well, sort of. I’d say my sump is approx same size but I will double check that. I’ll check what the old sump actually holds and compare it to mine as the old sump is an odd shape so can’t easily calculate it. The spec says that it should need 5.7 litres and my sump will hold about 4.5 before the level is above the top of the sump (there is more space but my engine is slightly angled back so it’s 4.5L at that angle). I’ve not long pulled the sump off to sort the gasket leak out and it drained out around 4.5L, which didn’t include the oil in the cooler and filter so there should be around 5L total oil.

My Comma oil app suggests that the engine is 6.9lts to refill I presume that’s from dry.
What’s the height of the original oil pick up and sump height from the Jag.
I have a Snap on oil pressure gauge if you wish or can double check the pressure.

Do you have any photos of the sump your using and pick ups.

[Boost All The Dollys]

Oil was some off brand oil I was getting from the local garage. Can’t remember the brand name but wasn’t a more common one

A MANN brand oil filter, with an anti-drain back valve. Looks like oil is draining back from the oil cooler and through the bearings rather than the oil pump. Currently, it goes; oil pump-oil filter-cooler-engine, maybe I’ll change them round so oil pump-cooler-filter-engine in the hopes that it keeps the oil where it is.

Original pick up height was 120mm from sump mounting surface. I’m not sure on original sump depth but I think it’s was around 140/150mm. I’ll see if I can find an oil pressure gauge as not sure how local you are to me and don’t want to damage or accidentally lose your gear but thank you for the offer.

[Carledo]

Oil was some off brand oil I was getting from the local garage. Can’t remember the brand name but wasn’t a more common one

A MANN brand oil filter, with an anti-drain back valve. Looks like oil is draining back from the oil cooler and through the bearings rather than the oil pump. Currently, it goes; oil pump-oil filter-cooler-engine, maybe I’ll change them round so oil pump-cooler-filter-engine in the hopes that it keeps the oil where it is.

Original pick up height was 120mm from sump mounting surface. I’m not sure on original sump depth but I think it’s was around 140/150mm. I’ll see if I can find an oil pressure gauge as not sure how local you are to me and don’t want to damage or accidentally lose your gear but thank you for the offer.

I have a Smiths combined oil pressure/water temp guage which has a duff water temp section (why I changed it) but I KNOW the oil presure guage bit is spot on because cuts off at exactly 60psi max on a fresh built Robsport Sprint engine. Yours for postage costs if you want it.

I can't visualise the sump as i'm not that familiar with this engine. And am confused by the oil level being level with or above the sump gasket, which would normally be wrong on several levels. Is it a 2 piece sump with an ally upper section and a tin lower well? Also you've mentioned the engine tilts in situ, is this side to side or front to back and is the main oil well in the sump towards the front or the back of the engine?

Steve

[Boost All The Dollys]

I have a Smiths combined oil pressure/water temp guage which has a duff water temp section (why I changed it) but I KNOW the oil presure guage bit is spot on because cuts off at exactly 60psi max on a fresh built Robsport Sprint engine. Yours for postage costs if you want it.

I can't visualise the sump as i'm not that familiar with this engine. And am confused by the oil level being level with or above the sump gasket, which would normally be wrong on several levels. Is it a 2 piece sump with an ally upper section and a tin lower well? Also you've mentioned the engine tilts in situ, is this side to side or front to back and is the main oil well in the sump towards the front or the back of the engine?

Steve

It’s a single piece sump. The oil being level with the gasket is because the engine is tilted back by 4-5 degrees but is fairly rigidly mounted and doesn’t move. Main well is at the front of the sump. Here is the best picture I have of it at the moment:



a bit comes out to the side which holds a good amount of the oil and there’s a baffle plate in there to prevent the oil sloshing away from the pickup.

[Carledo]

OK I can see the "wings" on the sump to get extra capacity and that the top of the wings will stop the oil (in them at least) from sloshing about.

I can also see that the crank centre line is quite high up in the block, at least 3" or so above sump gasket level, so I would assume that no part of the crank or rods protrudes below the sump gasket when it's turning over.

But I AM a little concerned about the shape of the rear part of the sump having too shallow a slope to let the oil that's draining down run forward with the slope on the engine, combined with surge from acceleration sending oil backwards into that area, that you might get a lot of oil there with nowhere to go, being whipped up and sprayed around by the rotating crank. This may be a non-issue if baffles are there or it may be important, it's hard to tell from this distance!

I come from a drag racing background and, believe it or not, the reason the Chevvy V8s dominate is because they alone came from the factory with a rear well sump, so all the surge stayed where the oil was needed rather than exposing the oil pickup as a lot of front well sumps did, with pretty catastrophic results. So, when running a front well, I'm always aware of this and build accordingly! It's why, when building both the Carledo and the Dolomega,both of which have front well sumps, I kept the sumps original and modified the subframe instead! I figured if the design was good enough for the factory, it was good enough for me and I wasn't going to mess with it!

Admittedly that amount of surge is pretty peculiar to VERY high output engines in cars designed and built for a very specific purpose, ie rapid acceleration, but..........

I agree that having the sump protrude below the subframe is not a good idea, both the Carledo and at least one Vauxhall redtop powered car that I know of feature this and one has to be a bit careful with sleeping policemen and the like. The Redtop car actually wrecked his sump on some road irregularity and I had to sell him a spare one. But the Carledos sump has only suffered a few light scrapes in nearly 60k miles cos i'm careful! Knowing of the weakness is almost as good as curing it!

Steve