[joe baring]

Hello I have a case 448 with a onan pc18g engine. It runs fine with it brand new nikki carb, but there is a noticable ticking noise in the engine. I know its not a knock as it is quiet but noticable. There is no lose of power or engine problems at all. In fact if you were wearing headphones you would not know the ticking existed. The engine tick is very rythmic and when you rev up the engine the ticking rate speeds up as well. I changed the oil with 1 quart of sae10w30 and the dipstick reads perfectly full. All help is very appriciated. Thanks guys for supporting this great forum and have a great rest of your day! I can send pictures if wanted of the 448 later.

 

[k0jdd]

Could be that the valve lash needs adjustment.

How many hours on the engine? Have the heads ever been de-carboned?

It could be that it is just time for some regular maintenance.

 

[Ray_McAvoy]

Welcome Joe!

The oil capacity of the P-series engines with the low profile oil base (that fits these tractors) is listed as 1.8 quarts with filter in the operator's manual. If you only have 1 quart in there now, it's low.

The Onan engines have a tendency for the oil to level to show higher than normal on the dipstick if you simply pull it out and look at it. To get a true reading, you have to pull it out, wipe it off, re-insert it, and pull it out again. If it still shows full with only 1 quart when following that checking procedure, you might have a mis-matched dipstick & tube. There were a couple designs for the P-series with one placing the cap farther outboard than the other and that resulted in a couple different dipstick lengths.

As for the ticking noise, it could simply be due to the engine being low on oil. But things like the valve lash & carbon build-up that k0jdd listed could definitely be the cause. Also check for exhaust leaks as those can sometimes make a ticking noise as well.

 

[Georgia SS]

Welcome Joe!

The oil capacity of the P-series engines with the low profile oil base (that fits these tractors) is listed as 1.8 quarts with filter in the operator's manual. If you only have 1 quart in there now, it's low.

The Onan engines have a tendency for the oil to level to show higher than normal on the dipstick if you simply pull it out and look at it. To get a true reading, you have to pull it out, wipe it off, re-insert it, and pull it out again. If it still shows full with only 1 quart when following that checking procedure, you might have a mis-matched dipstick & tube. There were a couple designs for the P-series with one placing the cap farther outboard than the other and that resulted in a couple different dipstick lengths.

As for the ticking noise, it could simply be due to the engine being low on oil. But things like the valve lash & carbon build-up that k0jdd listed could definitely be the cause. Also check for exhaust leaks as those can sometimes make a ticking noise as well.

I would assume if we are talking about an ONAN P engine, no mention of oil filter chg. probably if the engine has been run with only 1 qt.of oil at low RPM the piston pins are not getting oiled too well, so some wear on the rod small end will make a nice tap, get that 10w30 out and put in 2 Qt. diesel 15w40 and a half bottle of good old STP in blue bottle, been there, keep some RPM's up a bit and go on with work.

 

[Bob MacGregor]

Some info about Onan twins:
The static (engine not running) engine oil level is above the bottom of the dip stick tube. As the engine cools, the air above the oil in the dipstick tube contracts drawing oil up into the tube. This is particularly on Onan P series engines but not limited to them. Onan P series engines, 16, 18, and 20 HP models with the standard oil base will take 3 pints of engine oil in an oil change where the oil filter is not replaced and more if the filter is changed.
The lubrication system on aluminum block Onan twins provides oil under pressure to both crankshaft bearings, both connecting rod bearings and the front camshaft bearing. The rear camshaft bearing and the tappets are lubricated by splashing oil when the engine is running. Running these engines at low engine oil levels causes less or no oil to get splashed onto the rear camshaft bearing and tappets. In time the rear camshaft bearing wears into an oval shape. As this bearing continues to wear, the camshaft moves from side to side as the engine is running and makes a ticking noise. As the camshaft turns, it is moved from side to side by the force of the valve springs.
If during a valve adjustment, it is noted that the adjustment in not repeatable, then the rear camshaft bearing is worn excessively. Onan has an upgraded bearing replacement for this bearing, however replacing it is involves a major tear down of the engine during which other areas of the engine may also need to be addressed.

 

[joe baring]

Thank you everyone for your help! I have only run this engine low on oil for probably less than an hour. Do you think much wear has been caused on the bearings? If I put the correct amount of oil in it (1.75 quarts)now will the ticking stop or has damage already occurred. Can I feel with my hand if there is play in the rear baring or is it so small that I wont be able to. Also different topic to adjust the valve clearances do just take of the 2 covers underneath the intake manifold and use a feeler gauge to adjust it or is it more difficult to reach than that. Thanks everyone for your help you have been extremely helpful! Here are some pictures of the 448.

 

[Ray_McAvoy]

Hi Joe,

Topping up the oil level may or may not eliminate the ticking noise ... all depends on what's causing it. Having run it low on oil for less than an hour probably wouldn't be enough to have caused any significant wear or damage (especially if it wasn't run under a heavy load), but I can't say for sure.

Yes, to adjust the valve clearance you need to remove the 2 covers underneath the intake manifold and use feeler gauges to check. I have always removed the intake manifold first for easier access and I think that might even be required to get those covers off. Once you have the covers off, rotate the engine to top dead center (timing marks are on the flywheel & front gear cover) on the compression stroke (both valves closed) of the cylinder you want to check / adjust. If adjustment is needed, use a 1/2" (or maybe 9/16" ... I can't remember for sure) open end wrench to hold the tappet from rotating and a 7/16" open end wrench to turn the adjuster screw. Unless the clearance was way off, it typically only takes a small fraction of a turn. Rotate the crankshaft one complete revolution to bring the other cylinder up to TDC on it's compression stroke and do that side.

Bob brought up a good point about the rear cam bearing. I don't think this is something you'd be able to easily feel by hand because of the valve springs pushing on the cam. But like Bob said, it would show up when checking / adjusting the valve clearance. So after you have made the initial check / adjustment, rotate the crankshaft through a few revolutions and then bring each piston back up to TDC on it's compression stroke and re-check the valve clearance. If it stays consistent, the the cam bearings are likely okay.

 

[joe baring]

Ok so first off thank you very very much Ray McAvoy for your help! You went above and beyond with explaining how to adjust the valves. Thank you also to everyone else who contributed. Ok I put the correct amount of oil in and additional .8 quarts and I have not ran it yet, but the dipstick shows very overfull. I left it over night then pulled it out and it was still overfull I reinserted the dipstick and pulled it back out 10 sec later it still reads overfull. Is this common for onan engines to read overfull, but they are actually fine? Again thank you guys so much for the help and have a great day!

 

[curtisfox]

Take a file and make a new mark on the dipstick. LOL...........Curt

 

[Ray_McAvoy]

You're welcome Joe!

As Bob and I mentioned earlier, these engines do have a tendency for the oil level to read too high on the dipstick if you just pull it out and check it, but reading it like you did this last time should have it showing correctly.

Onan had several different dipsticks for the various tube & oil base combinations. I can see from your pictures that your engine has the "inner" style dipstick tube which is correct for these tractors (the "outer" style runs into interference with the hood). However, it might not have the correct dipstick. There should be a part number stamped into the metal part of the dipstick. And if I'm reading the parts manual correctly, it looks like the "inner" style tube and the low profile / standard capacity oil base should take a part number 123-1637-01 dipstick. The "-01" part might not actually be stamped into the dipstick itself though.

 

[Bob MacGregor]

Hi joe baring,
Your pic of the engine data plate is missing the most important part which is the 5 digit spec number beginning with 109, if it is an I/10936G, then it is an Onan P218 setup as a replacement for the B48M that was originally in the 448. A potential problem that I see in your pics is the aftermarket oil filter, some of which can leak down and cause incorrect oil level readings.

 

[joe baring]

Ok so I went back today and got some pictures on the dipstick. The number is correct for the dipstick. Bob MacGregor what do you mean by some of the aftermarket filters can leak down and cause oil reading. Can you explain that further? Also in that parts manual does it mention the amount of oil it is supposed to take with and without a filter change. I Put in 1.7 quarts. I read somewhere that sometimes the valves get loose and make noise and you can just tighten/readjust them. Could that be my noise problem. My Kohler M20 is starting to do the same thing and I always put the right amount of oil in. Thank you all for your help thanks!

 

[Ray_McAvoy]

Hi Joe,

That's good to know that the dipstick # is correct ... takes that variable out of the equation.

Good eye on the oil filter Bob! You're right, that could be causing the incorrect oil level reading.

Joe, I believe what Bob is talking about is the anti-drain back valve in the oil filter ... not all filters have them. That valve is supposed to keep the filter full of oil (once it has initially filled). If the particular filter you're using doesn't have that valve (or it is defective), it can allow oil from the filter to leak back into the oil pan, resulting in a higher than normal reading on the dipstick.

Yes, if the valve clearance is excessive, it can result in a ticking noise. As I described earlier, the checking / adjusting procedure is fairly straight forward for these Onan engines. I'm not as familiar with the Kohler twins (such as your M20), but I believe the checking procedure is very similar. However, I don't think those engines have adjustable tappets so the adjustment procedure is a bit more involved ... you have to remove the valves and carefully grind the tips of the valve stems if you need to add clearance or replace the valves if you need to reduce the clearance.

 

[joe baring]

I will get a new oil filter. The oil filter on it is defenetly the wrong one it sticks out of the engine much farther than other 448s. Also it has no tag or number that I can see on it so it could easily not have the valve. Although that would not be very good as from what I have read it keeps oil ready for when you start the engine and since it looks very old it may have already caused engine damage. I am hoping not. The guy I got it from was not very mechanically inclined so he may have never changed the filter. He used it to mow his huge rural property. So If that big oil filter where too leak all that oil back out it would make sense that the oil filter would read much higher. Am I thinking about this right or are there other factors. Also I heard that it could be a head gasket leak. Is that a possibility or would the ticking be much quieter. Thank you all and have a great day!

 

[joe baring]

Ok I went ahead and ran it again. I think I figured out my oil problem. The air filter says for changing oil with filter it is 1.75q, but when you don´t change the filter it is 1.25 quarts so I actually did overfill it because I put in 1.75q without changing the filter. (I will change it before I put it to work or run it much.) I ran it for a while and once it warmed up the ticking started again. This time a listened closely and it was coming from the left side. I am kinda stumped because I took a small metal rod and touched it to the engine and listened to the other end. I touched it to the valve cover and head and side panels and I can´t find the ticking. I can here the valves clicking, but nothing out of the ordinary. I still can´t figure where the sound is coming from. I am going to take the engine panels off and adjust the valves and do a deep check of where the ticking might be coming from. Thank you all very much for you guys help and support. I have learned a lot about these Case tractors from you guys. I could not have done any of this without your guys help! Thank you guys for your amazing help and I will be posting again in the near future. Have a great rest of your day!!