Oil Pumps

cgrey8 · Post by **cgrey8** » Fri Dec 07, 2007 1:08 pm

One of the things I've noticed about my Explorer motor's oil pump is it looses pressure when RPMs go sub-600. With an automatic tranny which is what every Explorer 5.0L came equipped with, that's never a concern, but in a manual tranny in stop-n-go traffic, I frequently put the truck in 1st gear, let the clutch out and just coast at idle speeds. Sometimes that's up a hill that drag the RPMs into the 500s. During this time, I can watch the oil pressure dropping to nearly nothing. It's probably just bouncing the sending unit and still giving flow, but a noted decrease in pressure would indicate a decrease in flow as well.

So the question is, should I replace the Explorer pump with a Mustang GT pump or an aftermarket high flow pump? Or perhaps is the time at "low flow" conditions minimal enough that it won't matter?

MalcolmV8 · Post by **MalcolmV8** » Fri Dec 07, 2007 1:25 pm

Most interesting. We have almost identical motors but mine has the 4r70w. With the tranny in Drive sitting at a light my rpms are at 500. I don't have a real oil pressure gauge so I've never noticed the drop you speak of. I just use the stock Ranger dash gauge which of course is nothing more than a fancy idiot light. It's either on or off but doesn't reflect real pressure.
Mine never bounces though so I must have enough pressure to keep the switch contacts closed all the time.

Malcolm

cgrey8 · Post by **cgrey8** » Fri Dec 07, 2007 1:33 pm

In that case, I'm not going to worry about it. It's probably just differences in the sending units we are using.

BTW, I too am using the dash gauge. However I tried to use what I thought was the Mustang GT modulating sending unit (big bell looking unit). To my disappointment, it doesn't work any better than an ON or OFF gauge. It runs my gauge up and it never moves or modulates unless RPMs drop or I turn the motor off.

cjcnomor4 · Post by **cjcnomor4** » Fri Dec 07, 2007 3:08 pm

most oe senders close below 10 psi. the mustang had a real gauge so the sender is different. we did have a problem with 00-01 senders sticking closed on cold starts at times, but would work ok after a few minutes of driving.

MalcolmV8 · Post by **MalcolmV8** » Fri Dec 07, 2007 3:10 pm

cjcnomor4 wrote:most oe senders close below 10 psi.

What is considered an acceptable PSI range? If I hooked up a real gauge and checked that is.

cgrey8 · Post by **cgrey8** » Fri Dec 07, 2007 3:11 pm

So is a sustained oil pressure of 7-8psi too low for idle loads?

plowboy34 · Post by **plowboy34** » Sat Dec 29, 2007 10:06 pm

I would never want less than 18 psi on the oil. Some people want lots of pressure but have seen bearing damage caused by to high of pressure. Pressure over 20 anywhere form idle to 4,000 rpm is fine. Over that you need a little more pressure. My John Deere Tractors only run around 25 and these engines are constantly on heavy loads. Never have cruising moments, they are alway's pulling hard. They only rev about 2400 rpm but they are under serious pressure. The psi needs to be read on a HOT engine, sure thats obvious but just wanted to make sure and point that out. I would also never want more than 60 psi on the oil, just puts a heavy load on the pump, shaft, distributor, etc. 40-50 psi is more than plenty of pressure.

Bazowak · Post by **Bazowak** » Sun Feb 10, 2008 7:04 am

Not sure where I read this but if memory serves correct the article said something like 10PSI per 1000RPM is a very safe margin to operate in.

If you run a high volume pump, make sure that the drain back holes are clear of any casting flash that would obstruct the drain back flow as most HV pumps put out about 25% more volume than a stock pump.

When ever I build something I always try and over build the oil system by using longer more capacity oil filters and also use filter relocators w/ #10 lines and when possible use an aftermarket oil pan and an oil cooler. All of this adds up to more oil capacity. It's extra money spent but it's also cheap insurance when comes to your engine.

Just my 2 cents worth.

cgrey8 · Post by **cgrey8** » Sun Feb 10, 2008 7:22 am

I agree. I wish I'd taken the time back when I was into my swap to install an oil cooler. But I didn't. It wouldn't be terribly difficult to do it now...except getting the motivation to go get the parts and have new hoses made up for the new lengths.

But more important, way above oil and fuel coolers is automatic tranny coolers.

Bazowak · Post by **Bazowak** » Mon Feb 11, 2008 12:22 am

cgrey8,

Don't have the lines made, make them yourself from AN hose and fittings. More on the expense side of things but you will be almost 100% assured that you will be leak free. I personal preference is the aeroquip sockless fittings and hose. Works great, way easy to use and stands up to oil,fuel,water up to temps of 300 degree and up to 200 or 250+ PSI. I would have to say that it is bombtastic. Check it out at Summit or Jegs. Summit has there own house brand that works very well too.

Transmission coolers I also do an overkill mind set. I always look for the biggest RV cooler and get that one then I go as far as even getting the Moroso heat sink single pass cooler as well. Always served me well and I haven't ever lost a trans mission due to heat. Now grenaded torque converters.......

I've seen in some of your other posts that have decided to move forward on the 331.......man that's awesome. I would really like to see pics of your progress as you do it. OH, and good luck on the house, 3 months should go by pretty quick, then it's sold. Take care and keep me posted.

cgrey8 · Post by **cgrey8** » Mon Feb 11, 2008 7:21 am

I've still got a binding contract. Closing is now set for March 21st. I'm just hoping nothing happens between now and then to mess that up.

It'll be nice to be out from under that place so I can finally start all the little projects that have been put on hold, and of course, start the not-so-little project of the 331 build and of course the shop to build it in. The wife wants the shop about as much as I do because the garage is so cluttered with my car stuff that you can hardly move around in there right now.

Bazowak · Post by **Bazowak** » Tue Feb 12, 2008 1:02 am

Man, I know what you mean by cluttered up garage space. I've got my turbo Ranger torn down and parts everywhere along with kitchen and bathroom renovation going on I need a shop as well. Talking about the wife......mine is getting upset that she can't use her side. Talk with you later.

V8-Ranger.com

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