• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Leaking oil pump??

Share this page

Nelson

Nelson

Jedi Warrior
Country flag
Offline
Yesterday we pulled the engine on my 948 Sprite because of an oil leak that we suspected came from my new five speed. It turned out that the transmission was not the culprit. We found this out after we repaired what looked to be the cause but when we started the engine after reinstalling it the leak was still there. Today the engine came out again. We can see the oil has come out at the oil pump and run down from there. The pump itself appears to be ok but why is oil running down from it? There is a small crescent cutout on the bottom of the pump and a small hole into the block at that point. It was manufactured there and we can't figure out what its purpose is or if that is the source of the leak why oil didn't pour out of it when I had the engine running in the past. I made a new thicker gasket and we put a thin layer of RTV on it that is setting up now. My buddy thinks that perhaps the leak is due to an improper gasket seal but I am dubious. Any thoughts would be greatly appreciated. Pulling the engine twice in two days already was not my idea of fun. Having to do it a third time would be way more than I can imagine.
 
Jack Laird will weigh in on the problems he's had with his BE. Sounds like you might to hear his oil pump stories and I'll bet he knows you to fix it. It will mean you will have 4-5 less times with the engine in and out than he has had getting the issue resolved.Glad to hear issue is not with the 5 Speed.
 
Quite possibly you are suffering from the back plate leaking as was the case with me. On some of the new oil pumps the case is physically larger than the stock units. This causes the oil pump to interfere with the clearance of the "can" and the pump. It puts pressure on the can and on a stock steel engine plate it cracks the solder joint and allows oil to escape and run down the out side of the plate and give the appearance of the rear scroll leaking on the alum back plate it appears the rivergate seal failed. Easiest fix is to put a piece of masking tape around the inside the can, bolt it up to the engine then remove it check for contact evidence .Some dremel time on the pump will allow for the required clearance. Then you will need to reseal the "can" to the back plate
 
I had a back plate gasket leak on a 1275 but for different reasons.
 
Chris said a mouthful there. The new replacement oil pump for the 948 (which have different bolt pattern that the 1275 oil pumps) are nothing more than 1275 pumps converted to kinda work on the 948. They work fine in the Mini FWD engine, but in the inline motor thay are too large in diameter to fit under the tin oil pump cover, and the exterior body of the pump has to be modified to work, it's goofy problem, no one has addressed. If your pump was not repalced, thn it could be that oil pump cover which is soldered to the backpalte may have came loose. If the cover seems to be secure, but you just have a isolated leak, then it is possible to repair without removing the backplate, by just sealing the leak, I'd probabyl use a epoxy for this like JB Weld, but if the cover looks loose, then I remove the backpalte, heat all the old solder off, clean everything good and re solder the cover back to the rear plate. I can never say I liked the oil pump cover arrangement on the thin rear plate on the 948 and 1098, the 1275 rear plate and cover were greatly improved.
 
A lot of the aftermarket oil pump manufacturers unified(minimized) their pump configurations. The old pin drive 3 bolt pumps had a different rotor/scroll configuration than the star drive 2/4 bolt pumps of the 1275. So, they standardised on the 1275 configuration (5 lobe rotor) and made a 5 hole body and milled off the bolt hole location at the 10 O'clock position when using them in a 948/1098 application. Most of the newer pin drive AE oil pumps I've seen for the 948/1098 had the 1000 bolt hole removed.

There is also a depth difference in the back of the block between the 948/1098's and the 1275 where the oil pump mounts. This can sometimes cause problems when using Cooper 'S' pin drive pumps in the 1275 in-line engines with various aluminum aftermarket flywheels.

FWIW, The 1098 transititioned to the 1275 style thicker cast type back plate of the 1275. Just watch out, the small journal 1098 back plates won't fit the later large journal 1098 back plates unless you use your portable jig saw and modify the flange opening. The small journal shares the same flywheel flange size as the 948. I also trim off the extra metal around the bottom part of the back plate while I'm cutting. This makes additional clearance for the 1275 type slave cylinders.

HTH,
Mike Miller
 
My oil pump was in use for about five years prior to my putting the Sprite into hibernation since 1973. There is a 1967 date on the pump. My backplate now is the aluminum one supplied by Paul A. with his five speed conversion. The pump is bolted directly to the rear of the block. There is good oil pressure - about 60 psi but a rapid drip with the engine running.
 
Depending upon what oil pump cover is used, you may have a slight mis alignment with the block and/or a sealing issue. There is a difference in the oil pump covers (948/1098 vs 1275). The 1275 oil pump cover being a larger diameter. If used on a 948/1098 block, it runs a bit closer to the edge of the block. The 1275 cover also has a raised "button" section on it to clear early style oil pumps. This could rub the back of the flywheel depending upon what type is used, wearing a slight hole in it. The 1275 oil pump cover also needs to be sealed in the recess of the aluminum backplate. What I do is put a light coating of silicone on the block around the oil pump opening. Then put the gasket down. Then put another coating of silicone on the gasket around the opening. The cover gets a bead around the lip. I put the cover in the backplate and then install the backplate on the engine.

Check all possible locations for rear oil leaks. Rear Main, including the little triangular piece. Oil galley plug at rear of engine. Oil could be leaking out the back one with the engine running and then coming down the other side of the engine. Also, could the rear side cover be leaking at the bottom corner? Trying to cover all possibilities.

HTH, Keep searching for the culprit. It's there somewhere!
Mike
 
A 1275 oil pump cover installed in a 948 backplate will definately rub a 948 stock flywheel. Mike you probably been working with aluminum flywheels, they give you more room. I just went thru all this with a 948 engine. The big difference between the two cover is the 1275 cover fit on the inside of the thicker 1275 back plate. Even if you bore the hole bigger on the 948 to fit the 1275 oil pump cver it's still too thick to miss the stock flywheel. Now many of us have used the 1275 rear plate and oil pump cover on the race cars with 948s, but in street car this is probably something you want to avoid, as it askew the alignament for the tansmission mounts.

Bottom line everyone is selling ths crappy onversion oil pump for the 948s, I just ordered two different one from two different suppliers, same thing on both account, even thought the second vendor swore it was what I needed. I ended up going back inspecting checking the clearnece on the stock OEM pump and cleaning and reusing it. I absolutely hate that BS solution they have came up with, and most of the vendors are clueless about it, because they don't actually install the parts.

It sunds like this poser, since he isolated the leak, probably doesn't have this issue, just some void in the soldering.
 
My pump has no soldering. The entire thing is just castings. The back part of it just sits on the front casting. It is strictly a metal to metal joint held together by the three mounting bolts.
 
Nelson said:
My pump has no soldering. The entire thing is just castings. The back part of it just sits on the front casting. It is strictly a metal to metal joint held together by the three mounting bolts.
Click to expand...

Nelson, you've got to have oil pump cover on the back engine plate, or oil will definatley leak out, it cannot be open to the area, it has to covered. If you can look at the backplate and see the oil pump with the backplate installed, you don't have the oil pump cover. Here's a picture of what it should look like. If you need a backcplate with the cover in tact on it, let me know I've got one. The 948 cover will have the word MOWOG on them as where the 1275 cover will not and have the smaller raised circle in the middle of them as Mike described.
 

Attachments

  • 21887.jpg
    21887.jpg
    59.7 KB · Views: 317
Thanks Hap,
The plate supplied by Paul A. for this conversion does not have a cover for the oil pump. It is exposed. I do have my original plate and it has the cover as in your photo. It does have MOWOG on it. Since it is part of the original plate and not on my new one would you suggest cutting it off the old one and mounting it on the new one?
 
OK, thats explains alot. The cover on the 948/1098 are actually soldered on the backplate, so you would heat them, a small propane torch would work and melt the solder to remove it. You may want to talk to Bill M. (didn't he take over for Paul A, forgive me if I'm wrong) the adapter plate for the Datsun tranny are thicker, much thicker than the even the 1275 backplate, much less the 948/1098 backplate, and whoever designed the backplate may have done it to work with either the 948 or 1275 oil pump cover (more than likely the 1275 oil pump cover, because that is more popualr engine choice). I've not worked with Paul A's plate, only Rivergate and they were designed to use the 1275 oil pump cover. Here's the deal, the 1275 oil pump cover is larger in diameter than the 948/1098 oil pump cover, so before you go and take the 948 oil pump cover off the backplate, do some measuring, because you may need a 1275 oil pump cover. This being a Datsun tranny coversion changes everything I told you above, with the exception that you need a oil pump cover. Here's a picture of Ray McCaleb's 1275 engine with the latest Rivergate backplate with the rear main seal, you can see even with the 1275 cover the plate is so thick, the 1275 oil pump cover hardly protrudes from the backside of the Rivergate rear plate. you just need to make real sure you get the right oil pump cover for that plate. If you have some dial calipers, you should be able to measure the hole in the plate where the oil pump goes, remove the oil pump if needed to measure, the 948 oil pump cover is roughly .350" in diameter, and the 1275 is somewhere around .380" in diameter. Hope this helps, but I think we are definately narrowing in on your problem.
 

Attachments

  • 21891.jpg
    21891.jpg
    54.7 KB · Views: 307
I'll be going to work on the car tomorrow so I can't do anything until I get to my friend's house. (50 miles from mine) Offhand I'd guess my plate is about 3/4" thick so it won't take much to do up a cover. My friend just wrote me that he has the trans already attached to the engine but it certainly can be detached again. Particularly since you feel that the lack of a closure behind the pump is the cause of the leak. Many thanks for your suggestions.
 
Hap- yes, I have Paul's stuff and YES there should be a can in there!
As far as I can tell Paul never supplied the can, that was supposed to come from the original backplate.
Thanks
BillM
 
Billm said:
Hap- yes, I have Paul's stuff and YES there should be a can in there!
As far as I can tell Paul never supplied the can, that was supposed to come from the original backplate.
Thanks
BillM
Click to expand...

Now the question is it made for the 1275 oil pump cover or 948, my guess is the 1275, because that would have been the more common application, unless there was a plate made specially for the 948 and the 1275, but either way, all he has to do now is measure the ID of the oil pump cover hole, and match to the above oil pump cover measurement to fiquire out which one he needs, they are 1/4" diferent in ID, so that should be easy enough to determine.

FWIW, Rivergate never supplied the cover as well, because everyone buying the kit normally had one.
 
Nelson said:
I'll be going to work on the car tomorrow so I can't do anything until I get to my friend's house. (50 miles from mine) Offhand I'd guess my plate is about 3/4" thick so it won't take much to do up a cover. My friend just wrote me that he has the trans already attached to the engine but it certainly can be detached again. Particularly since you feel that the lack of a closure behind the pump is the cause of the leak. Many thanks for your suggestions.
Click to expand...

I would not suggest you try to make a oil pump cover, unless your friend is expert sheetmetal fabricator anmd welder, and then still probably not, this thing has to be dead nuts on. Once you see what the ID is, you have several folks in your neck of the woods that should have plenty of spares, Rick Haynes in Columbus, at Sports and Imports comes to mind. You want to do this once, and do it right.
 
I see no reason why I can't use my old original piece as Bill M said. My friend is a certified welder and fabricated the cover that I have for my bendix gear on the starter but using the old one should be spot on. I just looked through my instruction sheets again and don't see any reference to the oil pump. It certainly is great having a pool of experts to tap into online. I don't want to do another engine pull.
 
See Nelson aren't you glad you joined this group. Already has saved you 4 - 5 engine pulls.
 
My question now is how do I attach the cover to the plate? There are no mounting holes.
 
Back
Top