Well, here I go... pulling the motor.

geordi · **Posted:** Sat Nov 16, 2019 9:36 pm

Much appreciated guys - I will be talking to him more in the near future, and I will pass all this info along. I don't yet know what his plans are, but maybe (just b/c the access is easier) he should try replacing the pump first. I'm kinda surprised that the wear would be an issue though, this is a gear pump and the pickup has a pretty fine screen on it. Anything that makes it through that screen should be well small enough to not bother the pump's gears, while bits of rocker should be WAY too big to make it through the screen.

Mountainman · **Posted:** Sat Nov 16, 2019 11:08 pm

geordi wrote:

Much appreciated guys - I will be talking to him more in the near future, and I will pass all this info along. I don't yet know what his plans are, but maybe (just b/c the access is easier) he should try replacing the pump first. I'm kinda surprised that the wear would be an issue though, this is a gear pump and the pickup has a pretty fine screen on it. Anything that makes it through that screen should be well small enough to not bother the pump's gears, while bits of rocker should be WAY too big to make it through the screen.

I dont know what its called, but pretty sure it's not a gear pump. Has an aluminum lobe that squeezes through aluminum channels, displacing the oil. Not a gear pump I think.
Then again, maybe it is a gear pump, but the aluminum is chewed up on many of the engines I open. The tolerance is smaller than the screen holes, and the steel debris eats the aluminum

geordi · **Posted:** Sun Nov 17, 2019 12:01 am

darn, that sucks. I wonder if there is an opportunity here for an upgrade that is more durable - at least we could do it without opening the pan. That could explain a lot about his engine, if the tolerance is small and the pump is chewed... Then it wouldn't be pumping as much.

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

The CRD has a rotor (or sometimes gerotor) pump.

https://en.m.wikipedia.org/wiki/Gerotor

The tight tolerances are required for their proper function, so any damage from foreign substances would have an immediate effect on efficiency. Some cars address this with really fine screens on the pickup, but especially with a diesel.i would think this could end up with sludge in the sump... Which is equally undesirable.

Diesel Dan · **Posted:** Sun Nov 17, 2019 2:07 am

geordi wrote:

To me, this is catastrophically bad, and it MIGHT just explain what happened with the second engine on my first CRD, which suddenly had a rod bearing failure in the middle of summer on a full charge of fresh oil. That one didn't munch the turbo, but suddenly started tapping after an Italian tuneup, and ended by stuffing the #4 rod through the side where the EGR had been. The rod cap had fallen off after the bolts backed out from the tapping after the bearing disappeared.

Thoughts?

Not about the low oil pressure but this failure you mention.

I've spun a few rod bearings in my day and never had a rod cap fall off. In one case we drove a SBC almost 30 miles knocking...bad. When I tore it down it only spun one bearing on a shared journal and wore the crank almost 1/4" and there was no bearing left. In another case we tried to blow up a 350 SBC and spun several rod bearings until it seized up. Rods turned blue half way up, bearing material melted into one piece. Almost sounds like the rod bolts/nuts weren't properly torqued and that may have been the root cause.

Diesel Dan · **Posted:** Sun Nov 17, 2019 2:38 am

Gerotor pumps are a proven design and used commonly in the auto industry.
Will they wear and by-pass internally? Yes, but so does a tried and true gear pump used in SBC/BBC engines. In the garage it was nothing for us to manually check oil pressure to confirm what the electronic were saying.

If I only seen 8 psi on the scanner a mechanical gauge would be step 2, 1 would verify oil level(seen that too).
Next step would depend which is easier by-pass spring, pump or pickup assembly. I've seen rags sucked up into a oil screen before. Since you have to drop the K-member to pull the pan I'd probably pull the pump and check clearances.

How the oil pressure acts cold/warm can help with the diagnosis too.
If the pressure drops of as it warms that usually indicates excessive tolerances/lack of sufficient volume.
If the pressure increases with engine temp I'd lean towards a pickup/suction issue. IE leaking o-ring at pickup tube, cloth rag in pan--as the oil thins it passes through that restriction easier etc.

On the pressure relief assembly, is the piston steel or aluminum?
It was quite common for the piston to seize on buick 3.0/3.8 front covers and cause 0 psi pressure from the piston galling the bore up.

Just some things to consider.

TKB4 · **Posted:** Sun Nov 17, 2019 1:41 pm

Also remember oil pressure is not the same as oil flow and varies with oil properties such as the weight though this doesn't seem to be the problem in this discussion.

Diesel Dan · **Posted:** Sun Nov 17, 2019 6:45 pm

Low oil pressure could also be from a massive internal oil leak.
Like on SBC, BBC loosing a galley plug behind the timing gear.
Now I don't know if the VM has anything like this though.

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

Sometimes worn bearings can cause low oil pressure - had an Audi with that problem. It was otherwise fine, but when the engine was hot oil pressure would drop very, very low. I believe it's some Mercedes diesel motors where damaged oil jets cause low pressure for the rest of the motor. All the Y2K-esque sludgy motors (Toyota, Audi, Saab) would "create" contaminated oil from ineffective PCV systems that would turn to sludge and obstruct the oil pickup. That was one of those worse when cold scenarios. On turbo motors proper PCV is positively *critical* - you gotta deal with that increased blowby.

IMO, the bypass valve theory doesn't hold water as it would tend to get worse with heat, not better, and it's probably mostly an all-or-nothing type affair.

My money is on the pump - it's either worn and not doing it's job, or its pickup has a problem and there are delivery issues.... a damaged o-ring, a clogged screen, etc. I would hook up a mechanical gauge to double check the sensor, but I'd wager that pan is coming off.

TKB4 · **Posted:** Mon Nov 18, 2019 4:18 pm

we had a mini cooper that had a coolant link via cracked plastic line next to firewall and it mildly overheated about 50 K ago and now oil pressure starting to get a little low think its from bearing wear. Has about 116,000 on it now its my daughters vehicle. New just put slightly higher weight oil i it like 10w/30 but not sure if it actually helps or just makes pressure look better.

layback40 · **Posted:** Mon Nov 18, 2019 4:36 pm

thesameguy wrote:

Sometimes worn bearings can cause low oil pressure - had an Audi with that problem. It was otherwise fine, but when the engine was hot oil pressure would drop very, very low. I believe it's some Mercedes diesel motors where damaged oil jets cause low pressure for the rest of the motor. All the Y2K-esque sludgy motors (Toyota, Audi, Saab) would "create" contaminated oil from ineffective PCV systems that would turn to sludge and obstruct the oil pickup. That was one of those worse when cold scenarios. On turbo motors proper PCV is positively *critical* - you gotta deal with that increased blowby.

IMO, the bypass valve theory doesn't hold water as it would tend to get worse with heat, not better, and it's probably mostly an all-or-nothing type affair.

My money is on the pump - it's either worn and not doing it's job, or its pickup has a problem and there are delivery issues.... a damaged o-ring, a clogged screen, etc. I would hook up a mechanical gauge to double check the sensor, but I'd wager that pan is coming off.

The early V8 Toyota Land Cruisers in Australia had a plastic oil pickup pipe & strainer. When they were worked hard like towing a van, it would soften & over time starve the engine of oil. I know an engine rebuilder that made a lot of $$$ out of that problem.

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

I LOVE IT when manufacturers take something tried & trued and modify it in a totally nonsensical manner and then hand if off to the consumer.

Plastic oil pickup has gotta be at least as bad as BMW's & Audi's idiotic fascination with plastic impellers on water pumps. Turn something totally reliable into a maintenance point that is pretty darned likely to just totally blow up your motor.

Diesel Dan · **Posted:** Mon Nov 18, 2019 6:56 pm

thesameguy wrote:

I LOVE IT when manufacturers take something tried & trued and modify it in a totally nonsensical manner and then hand if off to the consumer.

Plastic oil pickup has gotta be at least as bad as BMW's & Audi's idiotic fascination with plastic impellers on water pumps. Turn something totally reliable into a maintenance point that is pretty darned likely to just totally blow up your motor.

Funny thing, many prefer the plastic impeller on the LBZ+ vs the older Duramax models that had metal impellers.

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

I don't care what the material is, but on BMW/Audi the plastic impeller cracks around the axle you just suddenly lose all coolant circulation. If you're lucky, you just replace the head gasket. If you're unlucky, the impeller grenades then you're fishing tiny plastic pieces out of everywhere. :banghead:

My experience was just a head gasket, fortunately... but I don't imagine it would have been that simple if it had lasted a minute more!

flash7210 · **Posted:** Mon Nov 18, 2019 8:41 pm

You will find that the factory CRD water pump also has a plastic impeller.
Although it’s proven to be quite durable.

I didn’t change mine till 160k miles. And it was still in good shape and not leaking.

TKB4 · **Posted:** Tue Nov 19, 2019 2:42 am

I didn't change my water pump till 2nd TB change at 180,000 but I do like the Metal impeller on the replacement but I remember one post where the impeller wasn't attached to the shaft (? Sir Sam). There have been some bearing failures though which in itself isn't that big a deal but they caused slippage of the timing belt. Its all a problem of design give and takes.

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

I want all take, no give.

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

Got my next round of parts in late last week, so this week it's get the head on and test crank end play. FSM shows only:

1. Tighten all cylinder head bolts starting from the center bolts, following the cylinder head scheme and the following sequence:
3-2-1-10-9-8-7-6-5-4-11-12-13-14-15-16-17-18

2. Without loosening any bolts, starting from the center bolts, tighten each bolt an additional 75° in the following sequence:
10-9-8-7-6-5-4-3-2-1

3. Tighten the lateral cylinder head bolts an additional 50° in the following sequence:
11-12-13-14-15-16-17-18

4. Finally tighten all bolts an additional 75° in the following sequence:
10-9-8-7-6-5-4-3-2-1-11-12-13-14-15-16-17-18

There is no value for the first step... WTF? +125* or +150* is a big effing variable if there is no initial value.

Some research shows a lot of WAGs - but 22lb/ft (30nm) seems like a consistent number. Has anyone found concrete info on what the initial torque value is?

Mountainman · **Posted:** Mon Nov 25, 2019 7:22 pm

I don't know about your question, but

Getting those multiple "x degrees" torqued accurately is extremely difficult on this engine. You have to use a torque wrench that is designed to be used with the dial apparatus attachment, and then it's still pretty lame.

Also, unless I'm mistaken, the threads in the block must be clean and dry, and it is dang near impossible to get the oil out of them unless the block is upside down.
I have torqued the the rod bolts, which I believe have the same antiscuff coating without cleaning the oil out, and then with cleaning, and the oil definitely causes the bolt to turn too far. Overtorqued...

Oh, and you'll want to tap the block holes also to clean up the threads. ARP's save all that work

geordi · **Posted:** Mon Nov 25, 2019 7:47 pm

thesameguy wrote:

Got my next round of parts in late last week, so this week it's get the head on and test crank end play. FSM shows only:

1. Tighten all cylinder head bolts starting from the center bolts, following the cylinder head scheme and the following sequence:
3-2-1-10-9-8-7-6-5-4-11-12-13-14-15-16-17-18

2. Without loosening any bolts, starting from the center bolts, tighten each bolt an additional 75° in the following sequence:
10-9-8-7-6-5-4-3-2-1

3. Tighten the lateral cylinder head bolts an additional 50° in the following sequence:
11-12-13-14-15-16-17-18

4. Finally tighten all bolts an additional 75° in the following sequence:
10-9-8-7-6-5-4-3-2-1-11-12-13-14-15-16-17-18

There is no value for the first step... WTF? +125* or +150* is a big effing variable if there is no initial value.

Some research shows a lot of WAGs - but 22lb/ft (30nm) seems like a consistent number. Has anyone found concrete info on what the initial torque value is?

Are you installing bolts or ARP studs? And if you are using the factory not-to-be-trusted TTY bolts.... Then the question would have to be WHY? The ARP studs have proven themselves to be far more reliable in clamping performance.

Well, here I go... pulling the motor.

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