ONAN twin cylinder head temperatures

[JackC 616]

How about that. Great input.

Good thing you noticed. Those lights are small.

I like the loud horn idea. There is a wiring diagram out there for the 724-Z that should incorporate a relay and test switch.

The grass in flywheel screen is a real hazard for the 520H tractor and possible for the 416s also.

The grass flies out of the deck and gets sucked right into the flywheel screen and then the engine overheats.

Maybe the flywheel screen needs some kind of shield or the deck extension needs to be kept on. Mine are off.

Maybe SOI can come up with a recommended hook up with a relay so we can all add the loud horns to our twin ONANS 520s and 416s. It would be good if the test switch also tested the horn. 12V boat horns are really loud.

The temperature monitor we are working on can let the operator set the alarm temperature.

[JackC 616]

The temperature sensor that attaches to the ONAN head is no longer available from Toro or ONAN as far as I can tell. A different sensor would need to be used. Not sure what year they started putting them on the 520H. I believe the 1996 and 1997 years had them. Maybe they all did?

[Save Old Iron 1,563]

We just need to find one that has NORMALLY OPEN contacts.

http://www.ebay.com/...1-/250643518500

they are out there

[sorekiwi 761]

Maybe wire an ignition coil to a contact on the seat - that should get your attention!

Couldnt you wire a NORMALLY CLOSED sensor through a relay to trigger a light? We often use relays at work to switch the ground polarity on positive ground cars.

[Brian K WheelHorse 28]

You can run anything you want through a relay with a 12volt coil. Just grab 12volts from the + side somewhere to the switch/sensor and then to the coil. Then run 12volt through a set of normally open contacts on the coli to a light, horn, disco ball...whatever. I think I'm seriously gonna put something on there for an alarm though. Jack is right - the light is too small and it's partially obscured by the steering wheel. Kinda freaked me out when it happened.

[Save Old Iron 1,563]

http://www.ebay.com/...=item53ef2ebde7

110db - very loud

less than 1/4 amp draw - no relay needed

so, with a 170C (340 F) thermostatic button switch and a piezo car alarm, you have a $20 solution.

[JackC 616]

Great find. Looks like an easy add to any 520H with an existing over temperature sensor.

At 110bd, that is about as loud as a car horn. JC Whitney sells a car horn that puts out 125db.

Can't beat the price and it can be tucked behind the dash.

How about a wiring diagram to add it to the later 520hs that already have the sensor and the not so useful light?

It would be good if it can also be test triggered when the test switch is depressed.

[leeave96 487]

I have a question. I looked at my 1988 520-H and 1993 520-H and both have on the dash panel an Engine Temperature warning light. The manuals for both tractors say this light is for cylinder head temperatures.

My question is - has anyone lost a valve seat with the warning light OFF?

I like the idea of an alarm (or warning light), but it appears a warning light already exists on the 520-H tractors in the first place.

Is this engine temperature warning light a reliable/useable feature on the 520-H tractors? If so, we've already got an indicator we should be keeping an eye on during operation.

Just asking.

Thanks!

Bill

[Brian K WheelHorse 28]

I scavenged an alarm that works on variable voltage (6-28). It only draws 4-18mA so it likely uses less power than the dash light, which means no relay needed. This alarm pulsates so I should be able to hear it over the engine. I'll try it out over the weekend. Also - should work in series so it should be easy to wire:

Unrelated but I just found this pic of my modified hitch so I can pull my trailer with the 520H:

[Brian K WheelHorse 28]

I have a question. I looked at my 1988 520-H and 1993 520-H and both have on the dash panel an Engine Temperature warning light. The manuals for both tractors say this light is for cylinder head temperatures.

My question is - has anyone lost a valve seat with the warning light OFF?

I like the idea of an alarm (or warning light), but it appears a warning light already exists on the 520-H tractors in the first place.

Is this engine temperature warning light a reliable/useable feature on the 520-H tractors? If so, we've already got an indicator we should be keeping an eye on during operation.

Just asking.

Thanks!

Bill

I guess that's why this thread really caught my eye Bill. - I barely noticed it yesterday when my engine high temp light came on. It's partially obscured by the steering wheel. What if the idiot light doesn't work? It's a possibility that undetected high temperature conditions have cause some people grief with valve seat issues...

[leeave96 487]

Brian,

When your engine high temp light came on - what kind of work were you doing with your tractor? Were you under a heavy load or do you think something else caused it, dirty/clogged air fins or a bad heat sensor? What did you do about it? Did you park the tractor or unload it (stop working the tractor) and let the engine cool down while running?

I've never paid attention to the lights on the dash of my 520-H as I always have read they are troublesome and not very reliable. Maybe I ought to at least pay attention to the engine temperature light going forward!!!

Thanks,

Bill

[Brian K WheelHorse 28]

Brian,

When your engine high temp light came on - what kind of work were you doing with your tractor? Were you under a heavy load or do you think something else caused it, dirty/clogged air fins or a bad heat sensor? What did you do about it? Did you park the tractor or unload it (stop working the tractor) and let the engine cool down while running?

I've never paid attention to the lights on the dash of my 520-H as I always have read they are troublesome and not very reliable. Maybe I ought to at least pay attention to the engine temperature light going forward!!!

Thanks,

Bill

I was mowing at full speed and the air screen was plugged with leaves. I had cleaned it once before this happened (20 minutes prior) and I was surprised it had clogged again so quickly. I am going to make a fixed attachment so I can easily brush off the debris from the seat. I stropped, lowered the throttle/speed to 2000rpm, and wiped the leaves and debris off. The light went off in about a minute. I was a bit uptight about it because I just decarboned the heads, installed new gaskets and re-torqued everything. I don't think it was on long, but I don't want to add unnecessary stress to the engine, especially after reading about valve seat issues.

[Hydro 130]

Brian,

When your engine high temp light came on - what kind of work were you doing with your tractor? Were you under a heavy load or do you think something else caused it, dirty/clogged air fins or a bad heat sensor? What did you do about it? Did you park the tractor or unload it (stop working the tractor) and let the engine cool down while running?

I've never paid attention to the lights on the dash of my 520-H as I always have read they are troublesome and not very reliable. Maybe I ought to at least pay attention to the engine temperature light going forward!!!

Thanks,

Bill

I was mowing at full speed and the air screen was plugged with leaves. I had cleaned it once before this happened (20 minutes prior) and I was surprised it had clogged again so quickly. I am going to make a fixed attachment so I can easily brush off the debris from the seat. I stropped, lowered the throttle/speed to 2000rpm, and wiped the leaves and debris off. The light went off in about a minute. I was a bit uptight about it because I just decarboned the heads, installed new gaskets and re-torqued everything. I don't think it was on long, but I don't want to add unnecessary stress to the engine, especially after reading about valve seat issues.

....and that is I think how quickley it can happen! Before this investigation into valve seat failure, I never believed for a minute I did anything wrong. Now I think that was an honest statement but....all it takes is for your mind to wonder a bit while on the tractor with the flywheel screen plugged and before you know it, it's too late...the difference between hot and fatally hot,,,who knows exactly what that might be ....but it could happen that quick!

[varosd 1,185]

I too am perplexed as to why the Onan fly wheel screen attracts the leaves yet the Kohler screen is clear. has anyone noticed that if there really is a difference between using a side vs rear discharge deck? I am using my B-80 with the rear discharge and Parker sweeper for leaf duty.

certainly if the screen is covered , temps go up!

I wonder if adding black fine mesh on the outside of the screen would at least make it easy to scrap the leaves off while operating?

"Honey, do you have any old black pantyhose?" :D

[leeave96 487]

The Kohler Magnum 14 hp on my 314-8 catches a lot of grass, same as my 520-H. However, I have changed the flywheel side over to have a manual rope start pulley on it - the kind where you take a rope with a knot in the end of it, wind around the pulley and give it a yank (it has come in handy on a few occasions too). With the kit from Kohler for that pulley came a smaller screen with holes in it the same style as the K-series engines and I get a lot of grass sucked onto the screen. Before I changed over to the rope start, the Magnum engine had a plastic screen with huge holes in it. I was concerned with that screen that grass could get past it and lodge in the cooling fins.

One thing I saw a few weeks or months ago was a Gravely 4 wheel tractor - the type that have the engine mounted behind the rear wheels. It looked like that engine had a brush of some sort across the screen to keep grass build-up off of it. Anyone ever heard of one of these? Perhaps one could be adapted for the Onans.

Bill

Edit #1: I looked up a 16 hp K341 engine on Parts Tree for a Gravely tractor and they show item number 236847-S as a "Deflector" and it fastens to the engine shroud and spans the flywheel screen like a thin brush I guess to knock off debris that might get sucked onto the flywheel screen. Maybe this could be adapted to the Onan engines.

Edit #2: I noticed this engine temperature thread as labeled "Hot" as a topic... :laughing-rofl:

[Brian K WheelHorse 28]

Brian,

When your engine high temp light came on - what kind of work were you doing with your tractor? Were you under a heavy load or do you think something else caused it, dirty/clogged air fins or a bad heat sensor? What did you do about it? Did you park the tractor or unload it (stop working the tractor) and let the engine cool down while running?

I've never paid attention to the lights on the dash of my 520-H as I always have read they are troublesome and not very reliable. Maybe I ought to at least pay attention to the engine temperature light going forward!!!

Thanks,

Bill

I was mowing at full speed and the air screen was plugged with leaves. I had cleaned it once before this happened (20 minutes prior) and I was surprised it had clogged again so quickly. I am going to make a fixed attachment so I can easily brush off the debris from the seat. I stropped, lowered the throttle/speed to 2000rpm, and wiped the leaves and debris off. The light went off in about a minute. I was a bit uptight about it because I just decarboned the heads, installed new gaskets and re-torqued everything. I don't think it was on long, but I don't want to add unnecessary stress to the engine, especially after reading about valve seat issues.

....and that is I think how quickley it can happen! Before this investigation into valve seat failure, I never believed for a minute I did anything wrong. Now I think that was an honest statement but....all it takes is for your mind to wonder a bit while on the tractor with the flywheel screen plugged and before you know it, it's too late...the difference between hot and fatally hot,,,who knows exactly what that might be ....but it could happen that quick!

Totally agree. I am often so busy trying to keep my mow lines straight I don't pay attention to anything else - lol.

[Hydro 130]

I think a lot of us like the seat time because it is a no brainer when we are mowing. I don't believe there was a temp warning light on the 416.

[sorekiwi 761]

Not all 520's had the engine temperature light. My 1991 doesnt.

The "Test" switch is supposed to light up all the warning lamps so you can see if they are working.

I have mowed my property with both Kohler singles and the Onan, I believe the Onan does pick up more debri than the Kohlers, but it is a problem on both. Even when mowing grass I have to clear the screen every "lap" about every 4 minutes I'm guessing? (which is why I disabled my seat switch so I can lean forward and sweep off the debri with my hand without stopping. Dont do this on a Kohler - the screen on the Kohler is spinning with the flywheel!!)

There was a thread a few years ago about someone who had made another screen that sat a couple of inches in front of the Onan screen. It would get clogged reasonably quickly, but air could still enter the Onan through the 2" gap between the screens. I thought the thread was on here but I havent been able to find it since. Maybe it was elsewhere, maybe MTF?

[boovuc 1,090]

Very good thread!

My 520-H and 416-8 Speed pick up a lot of leaves this time of year. I "mulch" all my leaves with the tractors and just blow the bits around in the yard. I have 10 plus 50 foot + White Oaks and some Hickory so I have plenty of leaves. I find myself cleaning the screens on the Onans up to twenty times while I am mulching. Those engines suck much more air through them than any single or twin Kohler I ever owned. I can measure the volume through the Onans verses the Kohlers with a vanometer. Ours on the fume hoods at work are mechanical but are calibrated. Let me know if there is any interest in this.

Now here is the deal, I also have a 310-8, (single) and a C-175 8 speed with a KT-17 Kohler Twin. When mulching with these tractors in the same conditions, the Kohlers do not suck leaves in nor does the flywheel screen plug. It seldom gets one leaf against it.

Casual observation.............the Onans require a tremendous amount of air through their tins to keep them at running temps verses what appears to be a better design of the Kohlers.

Be advised that we are also looking at Onan aluminum blocks verses Kohler's cast iron. The Onan needs better cooling and less extreme temps to avoid warping. A cast iron engine can just plain take more extremes than an alluminum block engine.

I would love to design a coweling that would attach to a P series Onan that would allow the engine to draw air above the hood at maybe the operator's chest level. (Just for mulching season). Any Onan powered tractor and leaves in your lawn increase the chance of over heating. I am always cleaning the screen while I'm moving and sometimes it requires cleaning in dry high grass.

After mowing and with the engine cooled down, I stick the gas leaf blower through it. I also have a vented belt guard as well.

You can't be too careful with them.

[sorekiwi 761]

I can measure the volume through the Onans verses the Kohlers with a vanometer. Ours on the fume hoods at work are mechanical but are calibrated. Let me know if there is any interest in this.

I'd be interested in the results of this test - maybe measured at the same rpm for both motors (an Onan and a Kohler single). Also it would be interesting to wave the vanometer around a bit and see where the Onan is still sucking strong. It seems that the Onan manages to suck up a lot of stuff from down around ground level as well as directly into the fan. Actually thinking about this now I could probably just move a cigarette around and watch where the smoke goes...

[coldone 35]

Reletively cheap data logger, available with 2 thermocouple inputs.

http://www.supco.com/LOGiT%20Data%20Loggers.htm

Everthing thermocouple.I mean everything!

http://www.omega.com/toc_asp/sectionSC.asp?section=A&book=temperature

A quick cal check for thermocouple (TC) is to place them in a cup of ice water. The temp should read excatly 32F or 0C.

Dont trust the T1-T2 functions on dual channel Meters, they can be off a few degrees.

You can actually solder the thermocouple tip onto the piece that you want to measure temp on without effecting the measurement.

[Save Old Iron 1,563]

I can measure the volume through the Onans verses the Kohlers with a vanometer. Ours on the fume hoods at work are mechanical but are calibrated. Let me know if there is any interest in this.

One way of detecting air flow thru a conduit is with a manometer (Google it or look in the K series service manual ). Instead of a long plastic tube. a metal tube inserted into the airstream thru the engine could either be positioned to measure a slight vacuum or slight pressure relative to the air outside the shroud. When the airflow thru the engine decreases, the outside of the shroud and inside of the shroud pressures will equalize and trigger an alarm. This same principle is already used to detect a clogged air filter on the 520's.

Another mechanical version would be to hang a small "pie plate" off an arm on a microswitch in the path of the airflow. The airflow would lift the tin flap as air rushed past. When the airflow decreased, the tin would lower and trigger the microswitch attached.

[JackC 616]

The ONAN Performer series engines apparently need significant air flow to keep the engine temperature in a safe range.

The significant air flow also attracts significant grass and leaves onto the flywheel screen which apparently can lead to reduced air flow, overheating, and engine failure.

I do not believe the 416H has any over temperature alarm and I have heard of many 416H engine failures. I even bought one with a broken rod. The machine was used for mowing only and was not used for snow removal.

Some of the later 520H tractors have an over temperature sensor and light. The light is a "Micky Mouse" solution at best. The light is one of the little indicators in the column of lights on the left side of the dash. The over temperature light can be hard to see due to its position relative to the steering column and steering wheel. The zero turn 724-Z (I believe it was designed by Dixie Chopper for Wheel Horse and Toro) has a horn that will jolt you out of your seat when it goes off. The 520H should have had a similar alarm.

Lets face it, how important is it when your expensive ONAN twin is overheating, and by the way they don't make them any more, parts are getting harder to find, and shops that will work on them are even harder to find?

I believe we need to come up with a temperature monitoring device for our engines that allows the operator to monitor engine temperature, to set the alarm points, and also provides a "GRAB YOUR ATTENTION" alarm light or horn or both.

We may also need devices (shields or brushes) that allows the air to get to the engine without clogging up the air screen like it does.

The temperature monitor is a must.

[Save Old Iron 1,563]

I scavenged an alarm that works on variable voltage (6-28). It only draws 4-18mA so it likely uses less power than the dash light, which means no relay needed.

Brian, the Sonalert style beepers are certainly the noise maker of choice. The concern is if you can't find one in a surplus store, the device is over $40 to buy outright. A little pricey but if it saves a $1000 rebuild, then worth every penny. I have some 12 volt units from the 1970's still fully functional and are loud enough to be heard over a running engine.

[Save Old Iron 1,563]

These will work as sensors. They are not thermocouples and do not require $$$ of amp circuits to trigger a warning at 300F+.

I'll grab a couple and see how they perform.

http://www.ebay.com/...=item337d13d3f3

I should have looked at the specs more carefully. These are very high quality units but very delicate. The leads are not even insulated. I can certainly make these work, but for the average user, these may be too small and delicate to be installed without damage.

Continuing the search . . . . . . . .