Alternator/oil pump

[ZERO25]

As a business owner, I use Isuzu npr's. On one of my older ones, which has a 5.7l Chevy, it has an alternator with an oil pump attached to the back. Don't really know the reason, but theyre very expensive without the oil pump. My mechanic thinks the top of the engine needs extra oiling because of the temp and strain!

My point is......it seems like it might work in a racing application.Thoughts?

[SRXSRULE]

Pretty sure thats actually a vacuum pump for air brakes. It may have oil lines running to it also just for lubrication for the pump assemble.

[ZERO25]

Pretty sure thats actually a vacuum pump for air brakes. It may have oil lines running to it also just for lubrication for the pump assemble.

No sir, it has conventional brakes!

I was standing there when the mechanic took the oil pump off. He then started the truck to move it, the alt. would not be in until the next day. When he started it engine oil sprayed everywhere. Its def an auxiliary oil pump!

[dirtrace09]

The Isuzu NPR alternator/vacuum pump does have an oil line running to it but that is only to help seal and lubricate the pump. These pumps go out a lot due to vanes not sealing. It builds vacuum to operate all the different vacuum ports throughout the vehicle. A diesel engine doesn't produce vacuum like a gas engine does so they need this pump to make enough pressure for things like the brake booster, etc...

[fastford]

yep , and also it should have a vacuum hose/line coming off it....

[Jking24]

Mann.... i thought i was about to hear some crazy stuff id never seen or heard of before. Well that got grounded pretty quick lol. But seriously zero25 what benefit could you see an auxiliary oil pump in addition to the external pump we already have (essentially a second pressure stage on a dry sump pump) having? We already have pumps capable of providing enough oil volume for valvetrain oil sprayers piston squirters etc....

[ZERO25]

The Isuzu NPR alternator/vacuum pump does have an oil line running to it but that is only to help seal and lubricate the pump. These pumps go out a lot due to vanes not sealing. It builds vacuum to operate all the different vacuum ports throughout the vehicle. A diesel engine doesn't produce vacuum like a gas engine does so they need this pump to make enough pressure for things like the brake booster, etc...

The only problem is......this truck has a 5.7l (350 ci) Vortec Chevy gas motor!

The alt/oil pump is the only non-standard typical 350 Chevy part I have found! My mechanic says he tells his part supplier its a '99 Chevy truck! lol

[SRXSRULE]

Ive worked on a few of these trucks, even the ones with the 350 chevy.

Its a vacuum pump, nothing more. Has an oil pressure feed line and oil return line.

The Alternator driven vac pump is used for the power brake booster, exhaust brake if equipped, and various vacuum operated valves.

One more thing about these trucks with the chevy motor. If you live or drive much in the mountains its very easy to run them out of oil and blow up a motor. This is an engine braking deal and burning oil. I've never thought about it before but that vacuum pump could be the source of burning oil in a high vacuum condition during down hill engine braking.

[ZERO25]

Ive worked on a few of these trucks, even the ones with the 350 chevy.

Its a vacuum pump, nothing more. Has an oil pressure feed line and oil return line.

The Alternator driven vac pump is used for the power brake booster, exhaust brake if equipped, and various vacuum operated valves.

One more thing about these trucks with the chevy motor. If you live or drive much in the mountains its very easy to run them out of oil and blow up a motor. This is an engine braking deal and burning oil. I've never thought about it before but that vacuum pump could be the source of burning oil in a high vacuum condition during down hill engine braking.

Why would that motor need extra vacuum? Mine does have power brakes, but no exhaust brake or anything extra.

I asked my mechanic why couldn't I take it off and use a conventional alt......usually only Napa carries them. Luckily my town has a Napa warehouse and they usually have one in stock.

[Jking24]

Being the truck system was initially designed for a diesel with a vacuum pump the brake booster and other vacuum operated components may be designed to operate on more vacuum than the engine makes prompting izuzu to install the pump to ensure adequate vacuum at all times.

[ZERO25]

Being the truck system was initially designed for a diesel with a vacuum pump the brake booster and other vacuum operated components may be designed to operate on more vacuum than the engine makes prompting izuzu to install the pump to ensure adequate vacuum at all times.

Do you think I could take the vacuum pump off and run a reg alternator? The combo(without the vacuum pump) runs about $400 compared to $160 for a standard alt.!

[Jking24]

Do you think I could take the vacuum pump off and run a reg alternator? The combo(without the vacuum pump) runs about $400 compared to $160 for a standard alt.!

I honestly have no idea i don't have any first hand experience with them. But as a business owner myself my gut says take the 240$ hit versus having to potentially deal with unforeseen issues that could arise from a improper amount if vacuum. Especially since the primary system using vacuum is the brakes. A couple of inches of vacuum can make a big difference in the performance or lack of in vacuum brake system

[ZERO25]

I honestly have no idea i don't have any first hand experience with them. But as a business owner myself my gut says take the 240$ hit versus having to potentially deal with unforeseen issues that could arise from a improper amount if vacuum. Especially since the primary system using vacuum is the brakes. A couple of inches of vacuum can make a big difference in the performance or lack of in vacuum brake system

Its really not a money issue, just an availability one. Last month, napa was the only one to have one in stock. The time before, I had to have a shop re-build it, which took several days.(parts not local)

[Jking24]

If you have multiple trucks utilizing this setup and this is a relativity common failure on them i would talk to your regular parts supplier or the napa most of them will stock it for you. at least the parts houses around me will