Blower housing removal

[Dad520H 0]

You're right lynnmor, there is really no good way to install or remove without a filter socket. I've been using a WIX 51348 filter, but honestly I am really confused which filter to use. Soooooo many posts about many different filters. Not all of those filters mentioned have those "notches" on them for a socket.

Yes, I do have the shroud gasket. What is the purpose of this? To maximize cooling?

Thanks for any filter recommendations. 

[Dad520H 0]

I may never know why the leak occurred. I will use those filter numbers and come up with the correct filter. I haven't applied grease to the gasket in the past, but that is a good idea.  I'm just happy the problem appears to be solved. Now, that may be a different story once I install the blower housing. I hope not. Thanks for all help gentlemen!

Edited November 20, 2019 by Dad520H

[lynnmor 6,777]

I believe that all oil filter manufacturers say to put oil on the filter gasket.  That has been the advice I used for the past half century.

[troutbum70 857]

Every one has their method, I was mentored by my elders to smear a little grease on filter seals. 

[N875ED 98]

One other suggestion....pre-fill the filter (on your bench) about half full prior to installing on the engine. (More than half and it will run out since the filter is in a horizontal configuration when installed.) This will give a "head start" to the oil pump at filling the filter at first start after the oil change. The engine gets no lubrication until after the filter is filled.

[Dad520H 0]

Yes, I have done this practice for at least 40 years. It's a very good idea!

   I did not remove the flywheel to remove the blower housing,  but I may have to so I can get the blower housing back on. I sure wish  this tractor had a good ole Kohler on it 😪.

[Mudrig150 298]

Is...that a Deere logo on the hood?

Scandalous.

I like it.

[lynnmor 6,777]

35 minutes ago, Dad520H said:

Yes, I have done this practice for at least 40 years. It's a very good idea!

   I did not remove the flywheel to remove the blower housing,  but I may have to so I can get the blower housing back on. I sure wish  this tractor had a good ole Kohler on it 😪.

You really need to trade for a Kohler.  There is no need to remove the flywheel to remove or replace the blower housing on an Onan.

[Dad520H 0]

Ha! You caught that huh? Yep, I sold all of my Deere stuff and went back to old faithful. I grew up on Wheel Horse's, that's all my dad ever had. I had this Deere hood emblem.....as you can imagine, it makes some look twice!

[Dad520H 0]

As far as putting that blower housing back on, I just need to hold my tongue right I guess. 

[Mudrig150 298]

If you ever have trouble with the onan, and you want a nice opposed twin alternative, give a Magnum a try. They have a ton of standardized parts, were used in a lot of models, and are the cheapest opposed twins for rebuilding, mainly on account of the removable jugs (like a motorcycle).

If you don't care about any of that, go for a command.

[Dad520H 0]

Everything put back together, used Wix 51762 filter. I suspect my small oil leak over the summer was due to the wrong filter when I changed oil in the spring. My fault and I will admit it!

Thank you everyone for any and all input. I really do appreciate the help that comes from forums!

[Lee1977 6,217]

There isn't a way to change the filter on a 20 HP  Onan with out getting a little oil in the half round filter housing below the filter. That may be what you though was a leak. It need to be wiped out each time before installing a new filter. All the fins around the rear cylinder were caked full of oily dirt when I bought my 520-H last spring.  

[Dad520H 0]

Yes, a little oil will spill. I did have a small drip. I just never saw it because the dirt and grass clippings absorbed it. When I ran the engine with the blower housing off, I watched the oil drip. Most likely coming from the filter gasket.  I just mulched my big yard, took about an hour.  Not a drop anywhere. It's all in the correct filter. 

[Handy Don 10,596]

Resurrecting this thread after a year.

Another "new to Onan" (P218) guy with a lot of time on B&S and some Kohler with a "thank you" to @lynnmor. 

The notes here on getting the blower housing off and on the oil filter have been very helpful--I realized that my unit is missing the oil filter gasket at the blower housing so I'll have to get (or make?) one of those.

I was in disbelief that it took so many fasteners, disconnecting the throttle and governor connections, plus removing the air cleaner housing, and more to get that blasted housing off all while being careful not to screw up the nearby wiring.  You were right. Not fun at all.

Still, had to do it. A PO had broken off both "in" tubes on the fuel pump and tried to cheat the connection from the tank--it was sucking air. Got a new pump but there wasn't enough slack in the pulse hose to make the switch outside the housing. (I knew if I tried it the hose would slip loose, I'd mutter a lot of expletives, and then have to get in there anyway!) 

I'll replace the pulse hose and leave a bit extra, taking care that it doesn't go where it doesn't belong-like near those spinning fly wheel teeth! Also, once its open I can make sure everything else under the housing is clean and in order before putting it back together. Heck, I may even go ahead and re-seal the intake manifold as described in other threads while I have so much of this thing apart!

So simple fuel pump replace will take hours instead of minutes.

Any other suggestions while I'm in here? Check the pistons, maybe? See if the ohms are jammed up? 

[lynnmor 6,777]

The pulse hose can't be made much longer or it will buckle.  What I do is make it one inch longer and then cut off most of that inch when I attach the pump, that keeps it from falling back inside.

 

While you are tearing into this in a semi-major way, here are my suggestions to make it reliable for years to come:

 

Glass bead the exhaust and paint it with Rustoleum High Temperature paint.

 

Paint heat shields and other sheetmetal as needed with Duplicolor Engine Paint.

 

There is a place where a heat shield eats into the intake manifold, cut a bit of clearance.

 

Split and reseal the intake manifold only if you see evidence of leakage.

 

Adjust the valves, see last line below.

 

Clean and paint the valve covers, they collect debris and rust.

 

Clean under the engine so cooling air can cool the oil pan.

 

Replace the vacuum hose(s), if any.

 

Use all new genuine Onan intake, exhaust, head and carburetor gaskets, the Chinese ones will fail.

 

Use a torque wrench on the fasteners, over-tightening needs to be avoided.

 

Depending on how the engine was run and maintained, it might be time to pull the heads to decarbon and check the valve seats.  If you found the valve clearances off by more than a few thousandths, it might be a good idea to grind the valves and re-cut the seats.  Install new intake valve seals if you pull the valves.

[Rich16 32]

This post made me feel sane again - I just had the exact same problem and have the answer others have suggested - and beware about oil filter cross-references or what you think you're ordering (or getting). Always get the main ones recommended by others here.

 

Ebay offered up a 400hr 520h with a 60" deck for the steal price of $650 - and just 3.5 hours away - how could I refuse?

 

There was excess oil caked around the usual 'loose' oil drain pipe and beyond in the tins - more than made sense - but it ran fine getting it on the trailer and home though it wasn't well cared for and needed a lot of cleaning.

 

Lifted the engine up and tightened the drain with teflon tape - carefully by hand - and also ordered aluminum (light) replacements from McMaster-Carr for $28 incl. shipping to replace and try. Know some don't like teflon tape.

 

The engine oil was black & hadn't been changed in a long while so I changed - but forgot to change the filter. And here's where it started. The exact same problem where this thread began.

 

Oil filter felt like it was going on fine but impossible to really see. Hand turning with another 1/3 turn with the wrench - typical.

 

Cranked it up and - shocked - oil poured out the bottom with the oil light flickering. Huh? Like all of it. Some choice words as it was on the driveway and the pan wasn't situated right. Stopped it immediately.

 

A few bolts were missing where the back shroud meets the front & I didn't think much about it - but seemed someone was there before maybe with the same issue? Lots of excess oil caking.

 

Repeated everything, tight, did it all again - and all the oil poured out on the driveway - twice now. Why? Didn't do it the day before so what's going on?

 

So I pulled the engine today to figure this out and clean everything up - my friend from the Tuul crib in Nashville sold me a spare engine a few years ago that runs fine so why not just replace for now?

 

Was prepared for the worst and read of possible nasty rear leak causes here - but was having trouble getting the PTO completely off to transpose and decided to investigate the problem & just fix if possible.

 

Lots of oil soaked grass in the shrouds and along the back of the engine but nothing's loose & it's not coming from the crank area. Whatever is leaking was obviously coming from the oil filter area & spraying around it long before I owned it.

 

It WAS the oil filter - I'd gotten a case of 'em (supposedly the NN1043 compatible) from a reputable seller who sent the Stens 120-345 - scrolling way down it has the Onan p220 listed but it's not a good fit (and is the NN10147).

 

I swear I ordered the Toro 10143 'compatible' - maybe someone saw the Onan listed and thought it'd be OK? I wasn't paying attention.

 

Screwing the filter in looking right at it and it'd screw on two different ways - a wrong way and a right way but both 'felt' OK. Male engine threads looked fine & not cross threaded - weird. Filter threads look fine.

 

No doubt though - the filter threaded opening had just enough slop to go on wrong and feel like it was tightening normally - but wasn't and missed seating the gasket by 1/4". Problem solved.

 

With the filter lifted up a bit it'd screw in properly and seat OK (and probably work OK).

 

The excess oil everywhere had to be due to others not tightening or putting it in correctly and leaking.

 

Oh, well - it needed a thorough cleaning anyway and I learned about the shroud over the oil filter neither of mine have - going to fix!

 

And comments about oiling the rubber seal - yes! A wise old school mechanic some 50 years ago told me to prevent seizing the next time you take it off always rub some oil on it first - always have and never had any issues getting one off.

 

 

 

 

 

 

[lynnmor 6,777]

Sounds like you have it under control.  I will comment on the Teflon tape.  The issue is keeping the drain pipe from moving and the tape will only serve to make it easier to move.  All of my Onans have been repaired by tapping the engine threads just enough to get new and clean threads, followed by a thorough cleaning.  Then I screw the pipe nipple in using red threadlocker, yes red, if I ever need to remove and can't get it to move, heat will loosen it.

[Rich16 32]

14 hours ago, lynnmor said:

Sounds like you have it under control.  I will comment on the Teflon tape.  The issue is keeping the drain pipe from moving and the tape will only serve to make it easier to move.  All of my Onans have been repaired by tapping the engine threads just enough to get new and clean threads, followed by a thorough cleaning.  Then I screw the pipe nipple in using red threadlocker, yes red, if I ever need to remove and can't get it to move, heat will loosen it.

Lynnmor - thanks much and for all the help in the past.

 

I've read yours and other comments about the red threadlock and am just a bit skittish using it - I've had good luck with teflon tape on my other and if it doesn't work will go with the threadlock.

 

Another querie - I decided to get aluminum fittings since the 4" iron pipe with cap hanging off the nipple is too heavy and the weight is in the 'unscrew' direction and why this problem even exists. Any opinions about it? I assume no galvanic activity since it's aluminum in aluminum and the total aluminum piping is almost weightless - and why I figured teflon tape might be OK. And figured less chance of a weight related unscrewing. Maybe. and being oily anyway less chance of aluminum corrosion.

 

Haven't seen anyone doing this but it seems to make sense and less ??? chance damaging engine threads with aluminum pipe.

 

I did notice the teflon tape doesn't go around aluminum like iron - wants to slip and you have to hold the first turn down to wrap flat - it does go in fine though.

[lynnmor 6,777]

As long as you have the Teflon the aluminum threads will not gall.  If you want to do an upgrade, install a drain valve with a short piece of tubing. 

[Rich16 32]

20 hours ago, lynnmor said:

As long as you have the Teflon the aluminum threads will not gall.  If you want to do an upgrade, install a drain valve with a short piece of tubing. 

Lynnmor - really appreciate your and Cleat's help - always spot on & thanks for responding.

 

I've used my trusty 416-8 Kohler bought new in '85 without incident (as have many). Thought getting a 48" deck was a major upgrade.

 

My first Onan experience was only two years ago thinking the hydraulics would be easier with my bad arthritis & I'd read the pros and cons here. - but absolutely love it and when I get on my 416 it now feels pretty rough.

 

The main (520 lethal) forum issue over and over (aside extra maintenance) is the rear valve seat/rear cylinder overheating and I almost didn't get one because of it - and I'm always paranoid about it.

 

I'd joined the forum to find out more about this before purchasing & made the seller of my first one play a video to listen to it and be sure it sounded OK before even considering buying it.

 

Despite this latest glitch I'm a 520 major fan - I mowed 20 acres on our farm post bushhogging with my 48" deck - the guy who bushhogged said it was too thick to finish mow and thought I was nuts using my 'lawn tractor' - loved the look on his face a week later when he saw the place  & he wanted a closer look at the 520. Took about 4 half days to do. Many compliments.

 

So the rear cylinder issues - I took the belt guard off this latest acquisition to assess rear cylinder being clean & saw the oil caked issues - started it up and was astounded at the air velocity coming off the rear cylinder. I know others have posted about cutting slots and such but this is THE cause of all of this and the belt guard must be modified & should never be put on stock if you're going to use it for work - I'll never run my first one ever again with the stock one on. Amazing I haven't already screwed it up. Has this been brought up more and I missed it?

 

Have ordered two extra guards from AZ tractor and intend to cut rectangular slots where the rear cylinder it - and cover inside with wire mesh. Saw the slots post for cooling but it still would block significant air flow. Seems there's more about fixing problems posted on the site than fixing why they occur? Just wanted your opinion. It wouldn't surprise me if many of the other Onan 'problems' with valve adjustments, etc. etc. aren't related to chronic overheating that's too easy to fix? When I took the rear head off was surprised it's way better than expected with 400+ hrs. of abuse. Know there are other old non-Wheel Horse Onan machines with the engine mounted transversely with drive shaft forward - maybe because of the cooling issues?

 

I suspect doing this will cure 90+% of the more serious Onan engine related problems - what do you think?

 

 

 

[lynnmor 6,777]

I have 4 tractors with the 20HP Onans, non of them with modified sheet metal.  I bought a spare Onan that had a loose valve seat, turned our the cooling fins on the rear cylinder was totally blocked with a mud dauber wasp nest.  Was lucky in that I found it just in time and a .010” oversize seat was the fix.

 

My opinion is that the blower forces plenty of air and it simply takes a turn at the belt cover.  The modifications to the belt cover is mainly a feel good thing IMO.  If I were to modify anything it would be the bracket that is right at the engine.  I ran my Onans hard with 44” snowblower and 60” decks.

[Rich16 32]

1 hour ago, lynnmor said:

I have 4 tractors with the 20HP Onans, non of them with modified sheet metal.  I bought a spare Onan that had a loose valve seat, turned our the cooling fins on the rear cylinder was totally blocked with a mud dauber wasp nest.  Was lucky in that I found it just in time and a .010” oversize seat was the fix.

 

My opinion is that the blower forces plenty of air and it simply takes a turn at the belt cover.  The modifications to the belt cover is mainly a feel good thing IMO.  If I were to modify anything it would be the bracket that is right at the engine.  I ran my Onans hard with 44” snowblower and 60” decks.

Many thanks again lynnmor - makes me feel more comfortable about running 'em harder - especially now with the 60" deck after reading many negatives about it on the forum.

 

I really really like it & it's a beast compared to the 48's.

 

Deck had one bad bearing Cleat gave me the courage to take apart and fix - surprisingly easy & decided to spend $$$ and replace all the gauge wheels & de-rust/paint the bottom.

 

It gets pretty warm in summers here in West Tn - probably going to go ahead and modify a spare drive cover just to feel better - won't deface the original - I know keeping grass off the intake is the biggest reduced cooling issue when the engine heat light suddenly popped on & I realized the intake was covered. Ouch. Lucky lucky. Won't happen again.

 

Also noticed the rear head wasn't torqued correctly and some blowby around gasket next to valves - could you help me with the correct torque & sequence? Can't seem to find.

 

Really appreciate the helpful comments

 

 

[lynnmor 6,777]

Page 4-1 and 10-17 of the Onan Service Manual, be sure to download it.  I have 900 to 1600 hours on my Onans with few problems.  These engines were primarily designed for generator service and many were governed at 1,800 RPM.  They could run all day at WOT with the big flywheel/fan keeping it cool at half the speed we run.  That air movement is what sucks the grass and leaves and needs to be constantly cleaned.  I never tried it, but some have built a fender for over the left front wheel which is the source of much of the debris.

[Rich16 32]

Lynnmor - thanks for saving the day again - that service manual is invaluable and I don't know how I missed it.

 

The greatest problem with internet searching/forums is that they favor the bad - bad reviews, bad outcomes, disgruntled.... and it's easy to get distracted from the vast majority of people (like you) who maintain their equipment and don't have any problems - I confess to being much relieved hearing all this.

 

The guy I bought the latest 520 from (responding to this thread) also had a 416h he said he liked the best but blew the rear valve seat - of course - which further enhanced by worries. I bought the entire 416h off him too and am thinking of putting my 'spare' p220g on it - would be great if the wire harness would plug and play but seems I've read here that won't work & I'll have to rejigger some connections - will probably transpose the blown seat engine's connectors to the 20hp.

 

I'm probably one of the few left to have been introduced to Onans working summers at a foam rubber plant in maintenance during college in the 70's - they uses towmotors everywhere in the plant that all had Onans and I'd help the mechanics work on them - all ran on propane and all were run hard with few issues.