[DallanC]

I cant figure this out, I have a 400ex that is leaking oil at the oil cooler lines. I've replaced the o-rings, still leaks. This machine had stripped threads from a previous owner that I repaired with a heli-coil kit... I can torque it to specification just fine now. So, proper OEM o-rings and lines properly torqued. Still leaks.

You can clearly see the area is oily enough for dunes sand to stick, but you can also see where its dripping fast enough to wash away sand below the line junction. Really strange. I dont see any damage to either the case or line surfaces that could allow oil to leak past.


I'm not sure what to do next.. try a slightly oversized o-ring? Very slight film of black RTV on both surfaces before installing new o-rings? (I dislike rtv but sometimes its useful)

/boggle. I hate oil leaks.

-DallanC

 

[Here 2 help]

Two things...........

If the bolt holes were stripped; when you Helicoil'ed them, did you drill all the way through the case or stop at the bottom of the original hole leaving a blind hole in the case? If you drilled all the way through the blind holes, you migh be experiencing leakage past the bolt threads.

Since the bolts were stripped, it indicates over tightening possibly from the use of oversized o-rings; did you check the ear of the line connector to assure it was not bent slightly?

An oversize o-ring may solve the problem or it may make it worse. Is the hollow dowel in place? RTV may stop it for awhile, but not being oil and gas resistant, it will soften and push out over time. Use Hondabond or ThreeBond 1184 as a better alternative to RTV.

 

[DallanC]

All good points.

The hollow dowel, I don't recall seeing them. In fact after making the original post, I was looking over the parts diagram for new o-ring #'s and I noticed them on the chart, and added 2 to my order with the 2 new o-rings. So they're already on the way. That might be the cause right there, as the o-ring compresses against that surface as well.

I don't believe the ear is bent, I think I looked it over when I replaced the older o-rings in the initial leak. When the new parts get here I'll give it a very close inspection.

Good to know about Hondabond, I'll look into that.

As far as repairing the stripped threads, I stick with whatever the factory did. If there isn't a hole, I don't make a new one. In this case it was a blind hole repair. I actually bought a tap just for that repair.

Thanks for your time!

-DallanC

 

[DallanC]

PS: What pressure do the oil lines run at? One thing I just thought of is if I had some form of blockage in the oil cooler, it could put increased pressure on the lines causing a leak that might not occur under normal conditions.

I'll try carefully putting some air pressure through the oil cooler and see if any flow is restricted.

-DallanC

 

[Here 2 help]

Dallan - the dowels keep the lines centered and from moving as they heat and cool. Not having the dowels means relying 100% on the o-ring. The rod has a roller bearing on the crankshaft and oil pressure is low (maybe 12 to 20 psi at 5000 rpm) - the engine depends more on flow than pressure. The oil pump is a dual gear-rotor pump - the 'pump in' side is high pressure low flow and the 'pump out' side is low pressure high flow. Honda does not publish the oil pressure in any of it's service literature.

 

[DallanC]

Follow up:

New parts arrived: OEM o-rings and dowels. I finally got time to pull the line fittings. I expected more oil to drain out but it was minimal so good to know (it has fresh oil in it currently).

The line fittings did NOT have dowels. Along with what you said about the dowels keeping the fittings from "moving", they also hold alignment with the case. The ears looked good... I'm confident the lack of dowels allowing the lines to vibrate, rotate... move etc, is indeed the cause of the oil leaks. I did buy some Honda Bond, but decided to not use it at this time. I'd rather not use it if possible.

I cleaned the entire area thoroughly with brake cleaner and dried it so it will be easy to spot if any new leaks take place.

Thank you again for the help and sharing your knowledge.

-DallanC

 

[Here 2 help]

You're welcome - I hope it was the simple solution