Frigidaire Unimatic Oil Pump Seals - explained

[swestoyz]

Hello fellow AWers -

It's hard to believe I restored the '58 Unimatic about this time a year ago. During that write-up I had mentioned that I had plans to detail out the differences between the two Unimatic oil pumps, but more importantly provide cross reference information for both styles so folks had easy access to the correct o-rings for future reoperation of their mechanisms. We have a friend in need so I thought it was a good time to finally get this down on paper.

What we know is Frigidaire did a complete overhaul of the Unimatic oil pump at some point in the mid 60's. What I don't know is exactly when the revised kit was introduced nor their official reasoning for the revision. The January 1964 reprint of the SER-723 1947-1960 parts catalog still calls out the original style pump, so my best guess is the revised pump was introduced shortly after, judging by the part numbers used on the revised pump it (656 and 752 series PNs). The first instance of this kit popping up that I'm aware of is the 1971 Frigidaire Full Line Parts Catalog.

As for the reason why the revision was created - I suspect Frigidaire found that over time the original spring portion of the cap would give out causing the cover that holds the spring within the cap, against the bottom part of the seal, to blow out. Once this happens the oil would become oil soaked and the mechanism would be inoperable. This is pure speculation on my part but based on a few mechanisms that I have seen with this issue. This also gave them an opportunity to improve the pumping mechanism as well (see below).

The original service kit part number for the cap and seals was 5417162, which included a new cap, o-rings, oil seals (the mechanical seal), pump finger, and gasket. (photo 1 below, taken from the 1957 washer parts manual)

The revised service kit part number was 6591693 and introduces a completely new cap, new mechanical seal, and two new part numbers for the o-rings. (photo 2 below, taken from the instruction sheet from the service kit)

[this post was last edited: 10/12/2020-21:47]

 

[swestoyz]

During the restoration a year ago I decided to pony up for a used Parker O-Ring scale/sizing tool, to help pin-point with accuracy the correct replacement for any o-ring that would be required to restore any transmission or application with an o-ring. With this tool I was able to then cross reference the original sizes over to a Parker part number, that is universally used within the MRO industry.

 

[swestoyz]

Two pumps, side by side

With the sizing tool on hand, all four o-rings have been cross referenced over to the Parker number, which I've included below. Some distributors call these numbers "2 dash" numbers, dropping the "2-" and cross referencing then with the last three digits.

In the shot below I've placed the original pump on the left hand side, with the revised oil pump on the right hand side, with the Parker 2 dash part numbers for cross reference, as well as the Grainger (GWW) equivalent number that I used to buy replacement BUNA-N o-rings.

So this can hit the search engines, here's the listing that can be used for copying/pasting:

5417162 Kit (Original) ---

5433237 lower o-ring (large, thick - steel) 2-213 41uk89

5433233 upper o-ring (large, thin - bronze) 2-119 41uk17

6591693 Kit (Revised) ----

7529595 lower o-ring (small, thin - steel) 2-115 41uk13

7529598 upper o-ring (large, thick - bronze) 2-213 41uk89

From a service perspective, Frigidaire recommended that the oil pump o-rings be changed during ANY reoperation of the mechanism, as well as replacement of the gaskets. Often times the cork gasket itself is good enough to be reused unless you want to cut your own. If so I'd recommend a hole punch kit to get the correct side of the oil pressure line hole within the gasket.

 

[swestoyz]

So, what did GM solve with this kit? Two things:

1. The mechanical seal change is vastly superior. The seal no longer has an integral spring within the cap (see above) but instead relies on a spring mounted on the motor rotor to supply the necessary force for the mechanical seal to function. This change brings the bronze seal down to the lowest oil point in the whole mechanism at the base of the cap and becomes stationary with the steel part of the mechanical seal now part of the rotating mass, sealing around the motor shaft. This also ensures the motor splines are exposed within the sump and have proper lubrication as well. The original style has the bronze part of the seal mounted within the base of the drive shaft, with the steel part of the seal stationary in the base.

2. The pumping mechanism is also vastly superior. Rather than relying on the finger pressure against the eccentric part of the drive shaft, the revised cap now uses a two piece pump mechanism with a separate spring and vane. The pressure difference I witnessed during the '58 rebuild was dramatic in comparison to the pressure I saw with the '56 rebuild. [this post was last edited: 10/12/2020-21:49]

 

[sfh074]

Awesome ......

a type "A" Frigidaire mechanic after my own heart! Great job!

 

[swestoyz]

What I don't have an answer for is why Frigidaire changed the part number for the 5433237 o-ring. It's the exact same size as the revised 7529598 and is used in the exact same spot on the oil pump cap. In fact both parts that interface with the o-ring are the exact same diameter, the original steel part vs the revised bronze part.

If I had to guess they wanted it to be uniform from a part numbering perspective, and/or they changed the rubber material. It doesn't have the appearance of a Buna-N o-ring, but neither did the originals. Rubber material gurus may have better insight. [this post was last edited: 10/12/2020-21:52]

 

[swestoyz]

Oh, one more note about the changes to the mechanical seal. Both the bronze and the steel parts are different between the two kits and CANNOT be interchanged. The bronze part has a different machined relief for the thicker o-ring on the later pump and it will not seal properly if used on a later pump cap. Similarly the steel part is slightly wider on the revised it and has a larger relief machined into the backside for the o-ring, whereas the original does not have an opening for this necessary o-ring.

Original on the left in both photos, revised on the right.

I also wanted to include the full instruction sheet from the revised kit, as these instructions are not found in any Unimatic service manual that I've found so far.

 

[swestoyz]

So, does this mean the original pump is junk, or a ticking time bomb?

For us, it's neither. The chances of the cap blowing out the spring on the original style cap is slim, so much that if it hasn't blown out at this point it more than likely will be fine.

The original oil pump also produces enough of a supply of oil to the upper spin bearing that the mechanism will provide years of trouble free service. It just means that if you are going to use your Unimatic make sure to let it run for several seconds on pulsation BEFORE letting it rip into spin if the machine has sat for any given period of time. The revised pump will provide enough oil immediately to satisfy the lubrication needs of the spin bearing from a cold start.

So, if you are reoperating a mechanism and do not have an oil pump kit for a mechanism with an original style oil pump, have no fear. Replace the o-rings and you'll be fine.

And, I'll end this with an obligatory Unimatic action shot! These were taken this past weekend, a year since the original restoration occurred.

Enjoy any future reoperations, and happy Unimatic-ing!

Ben

 

[combo52]

Unimatic Oil Pumps

Hi Ben, Do we know how long the Unimatic mechanism was in production after 1958 for commercial washers and dry-cleaners ?

 

I suspect that FD improved the oil pump when lots of these mechanisms were being used in commercial service, GM-FD really started stressing quality and longevity in the 1961 and on time period in their laundry appliances.

 

John L.

 

[swestoyz]

Commercial Unimatics

From the literature Robert's posted in AE as well as comments he's made over the years, I believe the Unimatic was phased out of commercial use around 1964. With enough of those machines installed in commercial settings between 1958-1964 I imagine the bean counters got fed up with the warranty claims they were paying out to force the engineers to address the issue.

I'd love to get my hands on the Service Tips/Tech Talk that would have discussed this change.

Both commercial service manuals he has posted on AE (1959 and 1961) show the original style pump, so I'm not sure if the last 1964 mechanisms would have had the revised pump, or not.

Ben

 

[gansky1]

Well done!

This is a wonderful resource for future restorations, Ben, thank you for the thread and time it takes to put these informative posts up.  I have a couple of mechanisms around here that need re-operation this winter so I'll get my o-rings ordered.  

 

[Unimatic1140]

Hi Ben, I checked the Tech-Talks, it seems the new oil pump was introduced in 1962 and probably only used for the 1962-1964 line of Unimatic coin-ops. By '65 the Super-Duty (souped-up Multimatic) coin ops were introduced.

This is from the 1962 commercial washer tech-talk, I'll get it scanned sometime soon and get it into the library.

 

[swestoyz]

We have a winner! 1962

Robert, thank you! For me anyway, this helps clear up the timing of the revised pump as well as the production use within the commercial line when the Unimatic was the source of motivation. I'll look forward to seeing this added to AE.

Ben

 

[jetcone]

Yes

the redesign was made due to the pump finger springs' fatigue and snapping in half inside the oil pump. I have seen two units with snapped pump finger springs. I had read and I think Robert has found it in that piece of Doctrine that it was for the heavily used commercial machines but the two units I reworked were residential. Always nice to upgrade a home machine though. Eddies machine had such low use I am not rebuilding the pump at this time as I have one new kit left and will keep that for the Blackstone B-250 machine. 

What interest me is Ben's idea that the motor splines get lubricated. Must ponder that.

 

[jetcone]

Ben

Good point about never spinning a dry mechanism, that oil is designed to flow down and out so after being stopped a day I would always agitate the unit before ever attempting a dry spin !!  I see Robert slapping in the spin dial and wafting away all the time- "oo look its doing 1140"! BAD BAD BAD !

 

 

 

[Unimatic1140]

I see Robert slapping in the spin dial and wafting away all the time- "oo look its doing 1140"! BAD BAD BAD !

AM I hmmmmph! Never had that issue, and I use my WO-65 for extraction only all the time when I want fast drying if I've washed them in poor extraction machine (like Kenmore, Bendix, Horton, etc). I think it's more important to do that if the machine has sat for a very long time without use, the oil film doesn't evaporate off the bearing and would stay greasy for some time.

 

[combo52]

Starting A FD UM Directly Into Spin

I agree with Robert, the only thing that is going to harm the top bearing in the mechanism is water leaking in from a bad seal above, besides by the time the tub reaches 1140 the oil pump is pumping oil into the bearing.

 

John L.

 

[joelippard]

Nice Reading, thanks for all the work Ben!

 

[jetcone]

Ummm

thats an interesting question John, we will test that theory when I get the mechanism all together again. My gut tells me oil does not reach the upper mechanism in spin because part of the pumping is due to the agitate shaft and trunnion pumping during wash. The oil pump is not powerful enough to cause flow to the upper mechanism it needs that oscillation but we can put this to the test in a few weeks !!! I will video the mechanism in spin and wash.