Quick oil pump question

[Element]

Going to buy a new oil pump for the truck tomorrow ('87 350), and it seems simple enough...drop the starter and inspection cover, unbolt oil pan, take old pump out and put new one in. Only question I have is about the intermediate shaft - was recommended to me that I get a replacement shaft with a steel guide. Will it become apparent where that's supposed to go when I pull the old pump out?

Reason I'm replacing it is because as the truck warms up, pressure goes from about 42psi cold to lower than 5psi hot.

 

[82Scottsdale]

Mines doing the same thing im not sure if it was my oil pressure sender going bad or my pump

 

[dyeager535]

Be sure to post up your pressure readings after the swap!

 

[Element]

Be sure to post up your pressure readings after the swap!

Will do; probably won't get to do it until the coming weekend, though.

Probably a stupid question, but do I really need to unbolt the engine mounts and raise the engine to get the oil pan off?

 

[Jason4x4]

Will do; probably won't get to do it until the coming weekend, though.

Probably a stupid question, but do I really need to unbolt the engine mounts and raise the engine to get the oil pan off?

probably not, pan should clear. The shaft is what drives the oil pump off of the distributor, it will be plain as day when you take the pump out.

 

[4X4HIGH]

DO NOT buy a high volume or high pressure pump. There is no reason to install a new intermediate drive shaft for a truck application.

I'm afraid to tell you that i highly doubt a new pump is going to do anything for your oil pressure. There are a couple things that effect oil pressure. The first thing to remember is that the oil pump can only make as much pressure as the oil clearances will allow. The fit between the crank and bearings and cam and bearings is what directly effects oil pressure. There is a bypass spring in the oil pump that could get stuck but then you would have very little to no oil pressure at all times. If this engine starts with decent oil pressure and drops when the engine warms up it is eiher a tired engine or has diluted oil that needs to be changed.

 

[Element]

DO NOT buy a high volume or high pressure pump. There is no reason to install a new intermediate drive shaft for a truck application.

I'm afraid to tell you that i highly doubt a new pump is going to do anything for your oil pressure. There are a couple things that effect oil pressure. The first thing to remember is that the oil pump can only make as much pressure as the oil clearances will allow. The fit between the crank and bearings and cam and bearings is what directly effects oil pressure. There is a bypass spring in the oil pump that could get stuck but then you would have very little to no oil pressure at all times. If this engine starts with decent oil pressure and drops when the engine warms up it is eiher a tired engine or has diluted oil that needs to be changed.

It does the same thing with fresh oil, and I've put a can of Seafoam through the oil twice, same results.

I'd have thought that if the passages were clogged, it would start with low pressure, and as it got hot (and the oil thinned out) the pressure would go up. It'll run at 25-27psi while cruising, just drops way down when idling or driving at very low rpms, like around town. Doesn't smoke, uses very little oil between changes, and has plenty of pep (only about 88k miles).

I was just planning on buying a normal oil pump, since they're only about $15, and a new gasket, just to see what happens.

 

[sweetk30]

exactly what 4x4 said. plus with the others comments. i have seen it my self. new sender raised my gauge pressure almost 10lbs.

get a good mech gauge and check it first before all that work. and if leaving in truck permenetly get the copper line and ditch the nylon junk. and buy a decent mid range gauge not a 9.95 gauge.

and if you do. spend the extra on a 1 peice pan gasket kit. worth every penney.

 

[lectric80]

4x4high is giving you very good advice. Check the gauge first, as changing the pump is a lot of work for something that is likely a tired engine. In this case, if it is not the gauge, it will be a tired engine. Worn bearings causing lost pressure, yes the pressure will come up while cruising, but drop while at idle, and it will be higher while cold. If the gauge is not the cause, changing the pump might cause a 5 psi increase when warm, but not much more.

 

[ryoken]

change the oil and run some Lucas in it...

 

[cuervo]

Putting a high volume pump in a stock oil pan can end up sucking the pan dry(which then ends with dry main bearings. And, as someone has stated high pressure is not needed.

I would guess the oil was not changed at normal intervals and the clearances are out of spec now.