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  #1   IP: 76.172.41.141
Old 08-23-2011, 04:09 PM
Bruce A Bruce A is offline
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Leaking MMI Water Pump

Hi All,

I have just completed a valve job and water jacket plate overhaul (which originally started out as just a head gasket replacement). The engine now runs fine as we just completed about 8 hours of motoring with no problems and power is now restored due to the valve job. The water jacket plate bolts were very hard to seal but, after replacing one with a stud and re-seating three others with Permatex #2, instead of "Aviation Permatex", I have got the leaking somewhat under control but I guess I will never stop it completely.

The above paragraph is just for historical reference as the main reason for this thread is to explore a leaking water pump that is dripping water from the weep hole underneath. The pump is an MMI flange pump which I bought new from Moyer and have accumulated 80 hours on the pump. I don't know how long it has been leaking but from the corrosion on the pump and the mess below I guess it has been leaking for some time. I noticed the corrosion and mess on the lower block/oil pan while doing the valve job. Note that the pump is in a RWC seawater environment in So. California. I have spent so much money on this project that I am reluctance to drop another $50 on seals and shipping in order to rebuild the MMI pump. I have several questions regarding my situation as follows:

1. Is it reasonable to expect the MMI pump to last only 80 hours before requiring a rebuild?

2. I recently acquired a rebuilt unused Oberdorfer pump that I could swap for the MMI pump---is this pump as good as the MMI?

3. The rebuilt Oberdorfer pump referenced in the question above has a Zerk grease fitting instead of the grease cup commonly installed on these pumps. So my question--how do you handle greasing the pump with a Zerk fitting as access is limited--maybe some sort of remote but permanent flexible hose??

4. I have several grease cup fittings that I could use instead of the installed Zerk fittings but which system is better--the Zerk setup or the grease cup?

5. How often will I have to attend to the grease cup or Zerk arrangement in order to keep the Oberdorfer pump properly greased? The MMI pump does not require greasing but maybe that is why it failed so soon?


Any help/comments would be greatly appreciated.

Thanks.

Bruce

Last edited by Bruce A; 08-23-2011 at 05:03 PM. Reason: typo
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  #2   IP: 12.166.158.242
Old 08-23-2011, 06:23 PM
Kurt Kurt is offline
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I have to respond to this as I just may have some of the most experience around rebuilding MMI pumps (well, except for the MMI folks themselves). I had an unfortunate set of circumstances that required multiple rebuilds of MMI pumps - I used two on a fresh water cooling set-up. The unfortunate circumstances resulting in premature seal failure and water (and oil) leaks were: (1) bad assessory drive bearings resulting in pump shaft wobble and premature seal failure - I didn't figure out that I had a bad assessory drive until 3 pump rebuilds later and at my wits end (2) an early version of the MMI pump that, according to Don Moyer, had seals that were subsequently redesigned - mine had the first version of the seals and they apparently were prone to premature failure. You might want to e-mail or call Moyer Marine to discuss your pump if you have not owned it for long. When I talked to Don and Ken, they indicated that they had almost no experience dealing with customers who had rebuilt their pumps as they were so new (this was about two years ago). They had not even figured out the recommended preventative seal replacement interval on those pumps yet. That being said, the seals should last much longer than 80 hours. In fact, even on an Oberdorfer you shouldn't have to replace the seals more than every 3 or 5 years - depending on how much motoring you do.
(1) So, maybe talk to Moyer first.
(2) If you want to use the Oberdorfer, they are fine pumps (although I prefer the MMI pumps) and you can directly swap it with the MMI pump. Low maintenance, fairly robust pump, with the exception of having to 'keep it greased' and them being a pain to rebuild (but you don't have to do it often as I mentioned above).
(3) I'm not sure about the Zerk fitting. Doesn't really sound like a very good set up if you don't have decent access, but I'm not sure. The grease cup is easy to use. When I had my Oberdorfer, I just turned it clockwise about a quarter turn every few hours of engine operation (5 to 10 hours - whenever I thought of it). Once every three months I would take the grease cup off to make sure there was grease still in there and, if need be, added more. Now, that may not be the recommended interval for greasing this pump, but I converted to the MMI pump after having the Oberdorfer for only about a year so I didn't get to caught up with the maintenance of it. I always figured a little too much grease is better than none at all!
(4) The MMI pump does not require greasing because the shaft runs through pre-greased, packless ball bearings. This set-up eliminates some of the issues with the Oberdorfer, but I have found that once the water seal fails and starts leaking, it will fairly quickly result in failed ball bearings on the MMI set-up due to water intrusion into the ball bearings. Sometimes this will manifest itself with some grease (does NOT look like engine oil - much thicker) appearing around the weep hole. If this happens, your bearings are now shot as well and leaking grease and in need of replacement. Water intrusion into the bearings also tends to rust them out and result in them not spinning so freely, resuling in the cascading effect of both seals failing (water and oil).

This is just based on my experience. I would really like to see a recommended preventative maintenance schedule for the MMI pumps. The seals on these pumps are very easy to replace, but you really don't want to wait to replace seals until you see water leaking from the weep hole because by then you really are best served to replace the bearings as well as both seals. If you don't, one or both bearings are likely to not be functioning properly and will result in more premature seal failure.

PS: your water jacket side plate bolts should not leak at all. You really should solve that situation as you will eventually regret not doing so with all of the rust that will start appearing on your block. You didn't provide enough information for us to figure out what the solution is, but there are various things you can do such as use Moyer's water jacket side plate stud kit. I must say, when I took mine off for a cleaning I just used a little permatex and a new water jacket side plate gasket and experienced no leaks at all.

Sorry for the long reply, but I just had to give you some benefit from my MMI pump experience!

Last edited by Kurt; 08-23-2011 at 06:33 PM.
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Old 08-23-2011, 08:19 PM
Bruce A Bruce A is offline
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Kurt,

Thanks for the reply. That was very good information about the accessory drive. How does one determine that there is wobble in the accessory drive shaft?

Also, can the accessory drive be removed with the engine in the boat, I presume it can be removed (if you are a contortionist) but then maybe not. Did you replace your drive in the boat?

Thanks,

Bruce
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  #4   IP: 148.170.241.1
Old 08-24-2011, 10:45 AM
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ILikeRust ILikeRust is offline
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Yes, the accessory drive can be removed without taking the engine out.

I would first remove the alternator for better access - you have to take the belt off anyway, and the support arm will be in your way. So you need to take that off.

There are two bolts facing the rear end of the engine, which are on either side of the water pump, and which pass through the casting into the accessory drive to hold it on. All you need to do is remove those two bolts and pull the accessory drive straight forward.
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Old 08-24-2011, 12:03 PM
Kurt Kurt is offline
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No problem, Bruce - just wanted to share my experience as it was a real head scratcher! That being said, my situation was a bit unique in that my assessory didn't strongly manifest typical failing assessory drive symptoms such as a very noticeable "grinding" or "clacking" sound during engine operation. It did make some noise, but not much. There is information on the forum about how to check the integrity of your assessory drive. Basically, the bearings should not have play. You can take a piece of 2X4 or something similar and, with the engine running, apply some side pressure to the drive spool (where the alternator belt attaches to the drive) and see if there is a change in noise - meaning, if there suddenly is no noise or less noise from the assessory drive, you probably have play in your bearings and you need a rebuilt drive unit - available from Moyer. Very easy to replace the assessory drive. The most difficult part, depending on your comfort level timing the engine, is the fact that you have to remove the distributor and then need to reinstall it and get the engine timed properly. Easy for some folks, a mystery for others, but there is plenty of information about this topic on the forum. Good luck with this! Remember, a bad assessory drive causing MMI water pumps to fail is not a well documented A4 issue, but this could be because there are not a ton of MMI pumps out there in the fleet. Don Moyer actually told me he had never see a bad assessory drive cause water pump seal failure, but this could just be because no one has made this connection before. At any rate - changing out the assessory drive fixed the problem for me and I didn't have to continue rebuilding water pumps! I did become pretty good at it along the way though! Keep us posted.
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Old 08-24-2011, 12:25 PM
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ILikeRust ILikeRust is offline
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Ah yes, I see I neglected to mention removing the distributor.

But still, you can remove the accessory drive without yanking the engine out of the boat.
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