How hard is it to change out an oil pump

[marine02]

I cant figure out my oil pressure problem and I will probably change out the oil pump. Has anyone done this and how hard is it to do?

[PhilSine]

You may simply need to rebuild it.
The kit is $10-$15 depending on where you get it from. I just did mine a month ago and I had never attempted it before. I also replaced my sending unit just to be sure I get it all while I was down there. The whole project from beginning to end took about an hour. The rebuild kit came complete with instructions. When you buy the kit have some Vasoline on hand for pre-packing and lubing the new gears. It also says this in the Chiltons.

Good Luck.

[porkchop]

Like he said it takes not time at all. The only other thing you will have to do is smooth out the oil pump cover. That can be done by getting some sand paper and glueing it to a board or another flat surface. Then run the cover over the sand paper in a circler motion until smooth. This gets all the grooves out of the cover. Also if you need any help I am 15 minutes away.

[J4GRAND]

Do what PC says on the cover but use a fine emory cloth and some machine oil to wet sand the cover. Did mine before rebuild and it took all of about 10 mins. to get the grooves out.

[marine02]

Thanks it didnt take long at all...unfortunately I still have low oil pressure....so now I am thinking it may be the timing chain cover. does that sound about right??

[porkchop]

That ia a possiblity. How is your pick up tube? Was it new with the engine? I am sure it is but had to ask.

I saw you driving off base today, the wag is looking sweet.

[marine02]

I bought the pick up tube brand new...I'll check it again when i take the timing chain cover off. Thanks dude its a working progress....I may change the name to the money pit though

[ July 22, 2003, 07:01 PM: Message edited by: marine02 ]

[Wesdog]

Any chance the oil pressure relief spring and plunger could be stuck open? Just a thought.

Wesdog

http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/wesdog_avitar1.jpg

[marine02]

I changed the entire oil pump cover assambly.

[Wesdog]

Originally posted by marine02:
I changed the entire oil pump cover assambly.Before or after the oil pressure problems?

Wesdog

http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/wesdog_avitar1.jpg

[marine02]

after

[Wesdog]

Is this on a newly rebuilt engine and you have never gotten good oil pressure on it since the rebuild?

If so, did you prime the oiling system through the distributor hole with a drill and shaft and check the pressure before 1st starting the engine?

Wesdog

http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/wesdog_avitar1.jpg

[marine02]

It was a remanafactured engine I did prime it the pressure got up to around 10 psi I figuered it was cuz the jerry riged primer tool we made sucked..but my pressure stays low doesnt get over that.

[Wesdog]

I see that you are a helicopter engine mechanic so you know about engines. Sounds like there may be a problem internally with the assembly such as improper bearing clearences.

You're not getting oil pressure when the engine is cold or hot? Does the engine run without making odd noises?

You might pull the valve covers and check the oil flow to the top end. This requires minimal disassembly. I wouldn't run the engine without good oil pressure especially if it's new. Get a good shaft and drive the oil pump with a drill to check it.

Have you contacted the builder? Sounds like it may be time to start looking into warranty service.

Wesdog

http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/wesdog_avitar1.jpg

[ July 26, 2003, 08:57 PM: Message edited by: Wesdog ]

[Al Johnson]

Just to add to the above, if your oil pump is scored on the walls or has excessive end clearance, you will have bad pressure. (I think you already know this, but the obvious has to be stated.) If it turns out to be end clearance, it's possible to machine the timing cover down to reduce the end clearance to the desired .002"-.006". I did mine with a big flat file, carborundum wet/dry paper, and a steel flat. It was scary, but it worked well. I now have 25 PSI hot idle, and 55/60 PSI freeway on a fresh rebuild.

Good luck!
Al

[Wesdog]

Ok here's what it says in the manual:

*******************
Gear End Clearence Measurement:
This measurement determines the distance between the end of the pump gear and the pump cover. The ideal clearence is as close as possible without binding the gears. The pump cover gasket is 0.009-0.011" thick. Symptoms of excessive pump clearence are fair to good pressure when oil is cold and low to no pressure when oil is hot. If gear end clearence is excessive, install a thinner gasket. If gear end clearence is still excessive, replace the gears and idler shaft.

Gear-to-Body Clearence:
Insert a feeler gauge between the gear tooth and the pump body inner wall directly opposite the point of the gear mesh. Select a feeler gauge that fits snugly but can be inserted freely. Rotate the gears and measure the clearences of each tooth and body in this manner. The correct clearence is 0.0005-0.0025" with 0.0005" preferred. If the gear-to-body clearence is more than specified, measure the gear diameter with a micrometer. If the gear diameter is correct and the gear end clearence is correct and the relief valve is functioning correctly, replace the timing cover. If the gear diameter is incorrect, replace the gears and idler shaft. If the oil pump shaft or distributor drive shaft is broken, inspect for a loose oil pump gear-to-shaft fit or worn cover. Oversize pump shaft is not available.

Installation:
1. Install the oil pressure relief valve in the pump cover with the spring and retainer cap.
2. Install the idler shaft, idler gear and drive gear assemby.
To insure self-priming of the oil pump, fill the pump with petroleum jelly prior to the installation of the oil pump cover. Do not use grease of any kind.
3. Install the pump cover and oil filter assembly with a replacement gasket. Tighten the retaining bolts to 55 in. lbs. torque.
***********************

So there you have it. Oil pressure varies depending on the type/weight of oil used, temperature of the oil, condition and clearences of the pump assembly, restrictions on the pump inlet and outlet and how fast the pump is rotating. It is sounding like there may be a low restriction to oil flow on the pump outlet if you've checked the other parts. Low restriction could mean out of spec bearing clearences, missing oil passage plug or something like that. I hope it isn't a problem with the bearings. Checking the oil supply to the rear area of the top end by removing the valve cover may give you some indication of any problem with excessive bearing clearences. I am not very knowledgeable in this area so I'm hoping others will chime it to point you in the right direction.
The 1st time my 401 was rebuilt back in 1983 there was no oil pressure when the engine warmed up. It wasn't the oil pump. There was an assembly/parts problem and the engine had to be torn back down. I never got the entire story but it was fixed. The AMC dealership paid for it but it was not a good experience. The problem was with the shortblock and they took my whole vehicle to the place that did the shortblock and made them pull the engine and fix it. Took me years to get it all put back correctly after they got done with it.

Wesdog

http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/wesdog_avitar1.jpg

[ July 26, 2003, 09:01 PM: Message edited by: Wesdog ]

[spiderman]

I have a similar problem. new oil pump gears, everything has good clearance. Freshly rebuilt 401, I checked and double checked all clearances, and still, pretty weird. I think there is something blocking oil from getting up from the sender mount, somehow. Sometimes start it up, sit at 20psi. Turn off, immediately start it up again, and it will show no pressure. Let it run, the all of a sudden, it will jump back up again. And this is an aftermarket mechanical guage, the OE guage did the same thing. Before and after the rebuild. 300 miles on the rebuild so far, and no problems other than that so far.

[Wesdog]

If there is any leak in the pickup path for the oil pump, it could have a significant affect on your oil pressure. It will suck air instead of oil. I've heard of cracks in the pickup tube or where it screws into the block in the crankcase. Never happened to me yet so I don't have 1st hand experience.

Also, it is recommended by some to plug the filter bypass in the oil pump housing. I did this when my engine was recently rebuilt. BTW, these oil pressure problems illustrate the caution that is needed when modifying the oiling system with such things as an oil bypass line to the rear bearings. Ya gotta be careful what you do or bad things can result. Maybe I'm just paranoid after all the engine problems I've had in the past.

Wesdog

http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/wesdog_avitar1.jpg

[ July 22, 2003, 10:33 PM: Message edited by: Wesdog ]

[PhilSine]

Oh yeah, here another suggestion. It's a problem I'm dealing with. So far I have tried 3 local auto parts places looking for an oil pressure sending unit. There are 2 kinde. One is for an idiot light, the other is for a reactive guage like ours. So far, in 3 attempts at 3 different places I have gotten the idiot light one. The first one had a round screw connector on it. The second one was the same so I did not actually buy it. The third one had the right connector but turned out to be the same type of switch. CSK has the right one in the on-line catalog but it is not stocked or even shows up on the store's computers. This could be your problem or it could be a loose wire.

How does the engine sound when running? That is the true tell-all.

[Horny Toad]

Have you verified that your oil guage is working? I rebuilt my motor over the winter and had almost no oil pressure showing on the stock gauge. I installed a mechanical Autometer guage and now it runs about 20psi at idle and 40-50psi on the road.

HT

[spiderman]

This aftermarket guage is doing the same thing as the oe, before and after the rebuild. Next, I guess I will change the pickup tube the next time I have to change the oil. I inspected my old one before putting that in, but it had been replaced before, and I could not see any cracks or such. It looked really good.

[marine02]

Thanks for all the excellent info, I had checked my clearnaces and Relief spring and they are good, My plan now is drop the oil pan and triple check my pick up, (Is there a clearance on how far it needs to be from the bottom of the pan? I heard if you put some clay in the bottom install the pan and drop it you measure the indent.)I have the timing chain cover from my old engine so I will try that one. I will also try your suggestion Wesdog and plug the oil filter bypass. Is there any tech info on that? Thanks again you guys rock!

[jeepgod]

hey.. i have an ideal.. take out that engine.. and bring it by.. ill do some testing on it..

[marine02]

Originally posted by jeepgod:
hey.. i have an ideal.. take out that engine.. and bring it by.. ill do some testing on it..WoW, really that would be great, I'll go ahead and pull it out and you can pick it up tomorrow better yet I'll rent the truck and drop it off at your joint, take as long as you need, I want to make sure its good to go.

[Marvin Gates]

Just a suggestion, take the stock gauge and put it in the trash can and get a real mechanical gauge. My stock gauge said it had 0 to 5 lbs at an idle and 20 lbs going down the hiway. I put a real gauge on and it reads 30 at an idle and 50 going down the hiway. Just a thought! :D :D :D

[Wesdog]

Originally posted by marine02:
... I will also try your suggestion Wesdog and plug the oil filter bypass. Is there any tech info on that? ...Plugging the oilfilter bypass will force all the oil to pass through the filter. This will help keep metal particles out of the bearings but it won't help with your current low pressure issue. Also, you must do the necessary oil and filter changes when you plug the bypass because once the filter starts getting clogged it will affect your pressure and oil supply. Shouldn't be a problem if you follow a reasonable maintence schedule. To plug the bypass you remove the spring and little triangle piece, tap the hole and install a plug. I don't recall the exact size but it's something close to 1/4" npt.

I hate to see you pull the oilpan for nothing but I would also do it at this point. Carefully inspect the area where the pickup screws into the block. Wish I could give you more info.

Wesdog

http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/wesdog_avitar1.jpg

[marine02]

Originally posted by Marvin Gates:
Just a suggestion, take the stock gauge and put it in the trash can and get a real mechanical gauge. My stock gauge said it had 0 to 5 lbs at an idle and 20 lbs going down the hiway. I put a real gauge on and it reads 30 at an idle and 50 going down the hiway. Just a thought! :D :D :D Already installed the mechanical gauge it was the first thing I did after replacing the electric sending unit.

[Wesdog]

Sounds like your gonna have the timing cover and oil pan off. Checkout the oil passage that feeds the pump and the passage from the pump to the pressure sender. As was mentioned in another post there could be something restricting the outlet path between the pump and sender. Here's a photo of the opening where the pickup tube screws in:

http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/401pickup_opening.jpg

If the oil pickup is too close to the bottom of the pan it could restrict the oil feed flow and affect the pressure. This might happen if the pickup tube isn't seated properly in the block or the pan is dented etc. If the pickup tube isn't tightly seated it could leak air which will affect the oilpump pressure and volume.

Wesdog

http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/wesdog_avitar1.jpg

[ July 26, 2003, 09:07 PM: Message edited by: Wesdog ]

[Wesdog]

Here's a photo showing the extra long oil pickup tube on my 401. I have the 7 Qt oilpan so the pickup tube was lengthened:

http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/401Block3.jpg

Wesdog

http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/wesdog_avitar1.jpg

[marine02]

Thanks Wesdog, youve been a ton of help. The oil pan was dented I banged it out but may not have got it out all the way. I bought another oil pan that I will try out, it is in better shape. I'll make sure that the pick up is tight, would plumbers tape around the pick up be a bad idea? It is a screw in. Thanks again.

[Wesdog]

I'm not sure what type of sealant to recommend. Teflon tape would probably be ok just be conservative and make sure pieces of it can't get sucked into the pump. Were the oilpan dents in the area under where the end of the pickup tube is located?

Wesdog

http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/wesdog_avitar1.jpg

[marine02]

Yea it was right ubder the pickup I banged it out but wasnt able to get it all out.

[Wesdog]

That would be great if you found the source of the problem. If so you should be able to put the good oil pan on, replace oil and use a drill/shaft to see if you now get normal pressure. Make sure filter is full. Let us know what happens as you progress on this.

Wesdog

http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/wesdog_avitar1.jpg

[Wesdog]

There is a small hole on the top of the oil pickup that allows air to escape from the inside of the pickup. Make sure this opening is not blocked. Also if the oil level is not covering the pickup completely air will be sucked into that hole so make sure the oil level is correct. You could try adding an extra quart and see if it makes a difference.
Black RTV is also good for sealing the pickup tube threads just be careful not to use too much and put it on a couple threads back from the tube end so it can't get into the oiling system.
If after all your efforts you can't get oil pressure, the oilpump appears to be within specs and an internal engine problem is suspected, you can drop the oil pan and rig up an oil pickup into the block from a bucket. Put a large pan under the engine and drive the oil pump with a drill while watching under the engine for where the oil is returning to the pan. This may reveal where a problem is but it can be a messy sort of test and requires 2 people. I've never done this myself but my mechanic has.

http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/oiling_system.jpg

Wesdog

http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/wesdog_avitar1.jpg

[ July 26, 2003, 09:09 PM: Message edited by: Wesdog ]