I've been reading a lot of stuff about the 276/278 and was disappointed to find out that the oil pump is manipulated. I've never been a fan of variable flow oil pumps and have seen cam issues on BMWs that had this set up. It is done for energy savings is what I understand.

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Jim

I'll be pulling the heads this week. Seems they have to come off to change out the chains, guides, etc....

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Jim

If someone could please post the torque specs for the head bolts it would be much appreciated. I've got an older copy of WIS and it does not have this application on it. I have got a newer copy coming.

tia

I'm thinking that a combination of a bad cam adjuster and a variable flow oil pump is what damaged the cam and three rollers. If anyone knows how to disable the variable part of the oil pump and could post it I'd appreciate it. I don't want my oil pump to back down for nothing.

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Jim

Finally starting to go back together.

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Jim

Got heads bolted back on this afternoon and noticed the rear lobe on the exh cam was boogered up some so I ordered another cam. I'm not that impressed with this engine. Am I being unrealistic comparing it to the 606 in longevity? I don't care if it is a gasser I would not have expected to see the cam lobes chewed up some.

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Jim

No, you're not in my opinion.

The variable displacement oil pumps are used in quite a few engines nowadays and, like you, I've always been a little queasy about their adoption.

I've noticed on the oil pressure gauges of more modern cars when at high-speed the oil pressure gauge is showing half scale readings. I kind of like looking down and seeing the oil pressure gauge at 80-90 PSI full scale readings like my 98 Dodge truck with the Cummins engine.

Of course there's no way to definitively prove the variable displacement oil pump was the cause of your cam wear, but I'd certainly say it's a possibility. When the engineers are calibrating the operation I'd guess they're more concerned about extracting an extra 2/10's of an MPG to comply with an EPA fleet mileage requirement than they are about the owner of the car 300K miles in the future.

As I recall if the sensor that measures oil pressure fails the pump is supposed to default to full-flow, maybe you could just unplug the right sensor and force it into full displacement?

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98 Dodge-Cummins pickup (137K)
13 GLK250 (157k)
06 E320CDI (341K)
16 C300 (89K)
82 300GD Gelaendewagen (54K)

Thanks Tim.

I should fire it up sometime today.

I think it is the combination of the cam adjuster going bad (maybe allowing more reduced oil pressure to cam. and then the oil pump reducing flow may have led to what I'm seeing.

It was the lobes that had the indications on it. The cam bearings looked fine.

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Jim

Just finished up. No more cold start rattle. Starts, drives and runs out good with no cam timing fault codes. I ended up replacing both cams on bank 2 and about four or five of the roller followers. I purchased the ebay kit for the four cam adjusters, timing chain(s) and guides for $860. I could not bring myself to purchase four new MB cam adjusters for $1000/ea is reason I went with ebay kit.

Should be good to 400k now.

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Jim

My next step is going to be to see if I can disable the variable oil pump system. I'm thinking to hook the scanner to it, watch the oil pressure, disconnect the connector that to the oil pump solenoid and see if pressure stays up the entire drive.

I'll let y'all know what I come up with.

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Jim

Can anyone provide a definitive answer regarding whether the oil pump defaults to "normal" flow/pressure or to the "reduced"flow/pressure when the oil pump solenoid is disconnected?

I can't imagin them defaulting to the reduced flow/pressure but you can't tell these days.

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Jim

I disconnected and covered up (to protect) the connectors to the oil pump solenoid. Road test and only fault code was this system had electrical fault/open circuit. I'd rather my oil pump stay at the higher rate.

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Jim

I'm probably going to hook it back up today. The mpg has dropped a good bit since running it unhooked. We have, for a very long time, averaged at least 24 mpg, running it for a few hundred miles since I disconnected it I'm down to 20.x mpg.

I read one time how much hp an automotive oil pump uses up and it was higher than I would have ever imagined.

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Jim

I did a quick run to the MB dealer (150 mile round trip) and averaged a little over 22 mpg. I hooked it back up after getting back. I'm still on original O2 sensors so if I don't get back to 24 mpg after hooking them back up I'll change them out to see if that will help.

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Jim

Keep in mind that lower ambient temperature will impact fuel economy. Since you've been off the road for a while these late December temps may be to blame....

As I recall it's supposed to be something like 4-5% power savings? Pretty significant savings when you're chasing corporate MPG requirements.

I also seem to remember from hydraulics that pressure relief by-pass valves generate quite a bit of waste heat.

If properly done it seems like variable displacement oil pumps are worth the trouble.

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98 Dodge-Cummins pickup (137K)
13 GLK250 (157k)
06 E320CDI (341K)
16 C300 (89K)
82 300GD Gelaendewagen (54K)