Found the oil leak from h2O pump, but how can oil be coming from here?

Turbo DV8

Turbo DV8

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Mar 2, 2016
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Silicon Valley
Last night I cleaned the entire area with degreaser. This morning I sprayed the entire area with foot powder spray and ran the engine up to temperature. The oil is leaking from between the water pump cover and body, about 3/4" to the left of the rear-most pump cover bolt. As far as I can tell, there shouldn't even be oil behind there. There is NO oil coming from the weep hole. Shining a light into the weep hole shows a dry pump shaft; no oil residue. So the oil seal in the pump should be good. There is no oil in the coolant reserve tank, or radiator. There is no water in the oil. There is no oil coming from the pump O-ring between pump and crankcase. The water pump cover bolts are secure. How in the Sam Hill can oil be coming from the mating surface of pump cover and body? There is no oil behind there as far as I can tell.
 
Looking at the schematics for the water pump. The only thing I can see that might be the cause is a O-ring. Go on hondapartsnation.com part number 90670-GHB-610. #9 on the drawing. It appears to me to be a housing seal not a shaft seal. If it leaks the oil might be running on the outside of the water pump and coming out where you said. Just a thought. I am not a MC mechanic.
 
The drive snout of the water pump is tapered and it fits into a tapered hole in the crankcase. It is sealed by a large diameter, thin O-ring. There is no oil pressure here but with the bike upright, the bottom half of the O-ring is in crankcase oil. If that O-ring is leaking, running the engine with the bike on the sidestand can cause more of an oil leak because much more of the O-ring is submersed in oil.

I've made this repair on several Honda V-twins and the only way to be sure is to have the bike on a lift with the engine running at normal operating temp. After I cleaned that area with brake cleaner, I stuffed small pieces of a clean paper towel into the bottom of the tapered opening and when they came out soaked in oil, the location of the leak was verified. :)
 
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This is why I don't understand it. I degreased the entire area and coated it with spray powder, then warmed the engine on the center stand. No oil stained the area all around that O-ring, even on top, and no oil came out the weep hole. It just started a pin head-sized drop from the cover, just to the left of that rear bolt. There was a tiny bit of bubbling from the bottom of the oil cooler junction as the engine warmed, but it didn't turn into a leak. It looked like just remnants of oil from the leak ahead of it which ends up spraying on the oil cooler. Guess I'll clean it again and try again.
 
To access the O-ring that I think DirtFlier is referring to you have to remove the water pump. It is the large O-ring at #9 not the small one at #7
Sorry the attachment is so small. If you need a better view go to hondapartsnation.com and look up the NT700V water pump.
 

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Yes. One must remove the water pump to replace it, but one can see the junction between crank case and water pump, and no oil is coming from that point.
 
Short answer (because I have to go to work) is porous/fractured engine case internally where the four o'clock water pump bolt goes into the engine. I'll post more some other day with pictures. Honda's solution would be: remove engine, crack it open and replace the left half case. My solution: TBD
 
Does the water pump have a scar on dent on its bottom edge to show that you hit something at one time? I've never heard of the crankcase cracking at that point but anything is possible.

ps. Unless I'm mistaken, the crankcase halves are only sold as a set (2).
 
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The oil was leaking from between the mating surfaces of pump body and cover.

View attachment 11691


When I removed the bolts and cover, the bolt removed from the 4 o' clock position was covered in oil, and oil dripped out of the hole. There was no evidence of oil in the mump body proper, where the water flows, and no oil coming from the weep hole, so the oil seal in the pump body is fine.


View attachment 11692



I had cleaned the area and sprayed talcum foot spray to reveal any source of oil. Once the pump was removed, there was no evidence of oil having come from any point above this threaded boss.


View attachment 11693



From this angle, you can see the cylindrical boss which is threaded to accept the bolt. The hole is tapped to a depth which ends right about where the surface of the crankcase is.


View attachment 11694


Inside the engine, looking through the hole where the pump was removed from, you can see the upper portion of the cylindrical casting extends in to the case. Using a dental mirror, you can faintly see the fracture. Tough to get a picture while wearing a headlamp and holding the camera in one hand and the dental mirror in the other.


View attachment 11695




The fracture runs across the boss, then makes a right angle turn as it travels towards where the threads begin near the surface of the crankcase. Here, right in the corner, the texture of aluminum changes. I am thinking perhaps this is porosity, but I don't know. Not a great picture. I tried many times to get a good shot. This was the best worst picture.



View attachment 11696



The fracture must end where the threads begin in the rear of the boss, then the oil just works it's way past the threads, and out the mating surface between pump cover and body. There was no evidence of leakage at the mating surface between the end of threaded boss and pump body. It must be a very good mating surface. So as the oil warms, the oil just follows the bolt until it find a point of least resistance to exit, which happens to be between the pump cover and body mating surface.

The bike has 4,000 miles on it. One would think that it's a safe bet to buy a five year old bike with only 2,500 miles. Not always, it would seem. If I had bought this bike new, I would have put 4,000 miles on it within a few months, and this would have come to light within warranty period.

Since the oil is only coming from the threaded bolt hole, and it is not under pressure other than gravity, I am going to try just degreasing the threads really well with aerosol carb cleaner, and sealing the threaded boss and bolt with HondaBond or similar semi-hardening sealant. I may also counter sink the surface of the boss just enough to accept a tiny O-ring around the bolt, which will compress and seal between the pump body, boss surface, and bolt. Any thoughts?
 
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All I can see is "Invalid attachment" when I click on the attachment link.

Has anyone looked into this problem as it seems to be occurring more frequently.

As far as a fix goes I would simply put a non-hardening sealer on the thread (as you suggested) and see if that fixes the problem (I suspect it will)

Thanks Seagrass
 
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I couldn't open your attachments. I am skeptical about the cracked casing. I have seen many times what looks like a crack in an aluminum casting is just a casting mark. Hope your cheap fix works.

Mike
 
I am also unable to see the attachments.
I would be very reluctant to replace the half-case without exploring ALL alternatives.
I suggest that you seek professional advice on this one.
There are ways of solving such problems. Talk to an experienced engine rebuilder for a practical solution.
Liquid metal is one possibility.

Macka
 
It was purchased from a dealership with 2500 miles. The leak didn't start until a couple weeks ago at 4000 miles. The only place the oil could be coming from is past the threads, and the only way for it to get there is through a porous or cracked case. I'm sure there is an easy fix. It's just the uncertainty of whether it will pop up again on a long trip to South Padre Island I have planned starting after Labor Day. I have used JB Weld on a seriously cracked case under the clutch basket on my CX500. I went over a rock outside Grand Canyon and created a gusher. Drained the oil, back flushed the crack with carb cleaner with a paper towel on the other side to absorb the cleaner, then patched it up with JBW. It held for over 100,000 miles until I swapped out the engine.
 
My memories of working on Honda V-twin water pumps are not the clearest but perhaps one of those tapped holes goes all the way into the crankcase and isn't a blind hole?

I seem to recall that I had to use thread sealant on one of the bolts, perhaps the one at 4 O'clock position?
 
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It is a blind hole, but when peering through the water pump opening in the case with a dental mirror and light, I could see a crack along the slightly raised area where the threads would be located inside.
 
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