Onan 7.5 Quiet Diesel Generator Problem

[FIRE UP]

There's been a few on here and other RV forums that have taken the time and effort to remove (drop) the 7.5 units down and out the front of their coaches, to do various services on them. If I recall, it's not all that hard. Since I've not had to do it myself, I really can't comment on what's actually needed to do it and or, what's involved in the fuel lines/plugging etc.

But, it shouldn't be all that difficult unless you don't have a place to work, the tools, a floor jack and a few other odds and ends to make a job like this easier. You've got your 12V cables for starting, the 120VAC output lines (should be a plug), a fuel line, (by the way, I'm pretty sure there's NO return line 'cause there's a fuel pump on the gen and pulls the fuel to it so, there's no pressure in the system that would require the un-used fuel to return to the tank)

That's about it for disconnect stuff. Then, figure out the chassis that needs to be lowered and, it's out. I suspect it's fairly heavy though so, the obvious precautions of "be careful" need to be heeded.

As for "Kubota" placing that sensor where it's at and, making it "inconvenient" for service or replacement, well, that little 14HP Kubota is a widely used diesel engine in a multitude of applications all over the planet and, about 98% of the applications allow for that entire engine to be out in the open so, for those people, it's cake. But, for us "Onan" users, and based on all kinds of parameters etc, for placement, weight distribution, ease of access for oil check/slight maintenance etc., the area for that gen is about the best. But, for the ones who don't have a slide out gen tray as I and a few others do, it makes for one pain in the a$$ when things like that sensor issue pop up.

As for the starting point of that sensor wire, it's been waaaaaaaaay too long since I did the job so, I cannot help you with that. I'm pretty much suspecting it emanates from the ECM.
Scott

[FIRE UP]

Now, didn't someone say that you could change out the whole housing, instead of fighting with getting the sensor out in one piece and possibly not breaking this housing in the process?

Tropical,
The thermostat housing in that little Kubota is a two-piece unit. The upper 1/2 comes off without an issue and exposes the actual thermostat, just like on a regular car engine. But, the lower 1/2, is bolted on with three bolts. One of which is too long to completely remove due to the fact that it hits a part on the front of the engine. It's been too long so I cannot tell you just exactly what it hits but, never the less, it does hit it and, will not come completely out and therefore, will not allow that lower thermostat housing to come completely off, in order to replace it.

But, there's three remedies for this situation.

1. Back that troublesome bolt most of the way out, then cut it with a hack saw. That will allow for the lower part of that thermostat housing to be completely removed. Then, when you go to re-install a new one, you use a shorter bolt.

2. Remove the front of the engine which, involves many items I personally would not want to deal with due to the complexity of many of them.

3. Remove the cylinder head. That's way more easier than one would think. There's three injection tubes that require a 17 mm wrench, a few other odds and ends that are easily accessed and, the head bolts and, it's off.

Without a doubt, the fastest way is of course the cutting of the troublesome bolt. I really don't know why I didn't take that route. I could have very easily but, for some odd reason, I chose to remove the cylinder head. That route to me, was not hard at all. Now that I think back on it, I did realize that I could have cut that bolt. But, again if I recall, I might have thought that, cutting it and replacing it with a shorter one, might not have had enough threads to allow for a good purchase of threads on the head. At least that might have been my reasoning for not cutting it back then. If I had it to do all over again, no doubt about it, CUT THAT BOLT!!

Now, as stated previously, that sensor may, or may not be, a pain in the a$$ to remove. For some, it zips right out without issue. For others, like me and some others, IT'S WAR!! The smartest move I made in that entire operation was to heat the area immediately around that broken left over sensor part with my propane torch. Then, put that torch down and immediately grab a can of "Freeze" and spray that little broken sensor part.

I couldn't believe that, with all the torque that I applied to it prior to this procedure, it wouldn't budge. But, when I sprayed that freeze on it, with the surrounding area still really hot, I grabbed what was left of that sensor with my small micro sized pair of vice grips, that stub spun right out of there, like it was put in about a minute before, with anti-sieze compound!!! Imagine that.

Scott

[tropical36]

Originally Posted by FIRE UP

Now, didn't someone say that you could change out the whole housing, instead of fighting with getting the sensor out in one piece and possibly not breaking this housing in the process?

Tropical,
The thermostat housing in that little Kubota is a two-piece unit. The upper 1/2 comes off without an issue and exposes the actual thermostat, just like on a regular car engine. But, the lower 1/2, is bolted on with three bolts. One of which is too long to completely remove due to the fact that it hits a part on the front of the engine. It's been too long so I cannot tell you just exactly what it hits but, never the less, it does hit it and, will not come completely out and therefore, will not allow that lower thermostat housing to come completely off, in order to replace it.

But, there's three remedies for this situation.

1. Back that troublesome bolt most of the way out, then cut it with a hack saw. That will allow for the lower part of that thermostat housing to be completely removed. Then, when you go to re-install a new one, you use a shorter bolt.

2. Remove the front of the engine which, involves many items I personally would not want to deal with due to the complexity of many of them.

3. Remove the cylinder head. That's way more easier than one would think. There's three injection tubes that require a 17 mm wrench, a few other odds and ends that are easily accessed and, the head bolts and, it's off.

Without a doubt, the fastest way is of course the cutting of the troublesome bolt. I really don't know why I didn't take that route. I could have very easily but, for some odd reason, I chose to remove the cylinder head. That route to me, was not hard at all. Now that I think back on it, I did realize that I could have cut that bolt. But, again if I recall, I might have thought that, cutting it and replacing it with a shorter one, might not have had enough threads to allow for a good purchase of threads on the head. At least that might have been my reasoning for not cutting it back then. If I had it to do all over again, no doubt about it, CUT THAT BOLT!!

Now, as stated previously, that sensor may, or may not be, a pain in the a$$ to remove. For some, it zips right out without issue. For others, like me and some others, IT'S WAR!! The smartest move I made in that entire operation was to heat the area immediately around that broken left over sensor part with my propane torch. Then, put that torch down and immediately grab a can of "Freeze" and spray that little broken sensor part.

I couldn't believe that, with all the torque that I applied to it prior to this procedure, it wouldn't budge. But, when I sprayed that freeze on it, with the surrounding area still really hot, I grabbed what was left of that sensor with my small micro sized pair of vice grips, that stub spun right out of there, like it was put in about a minute before, with anti-sieze compound!!! Imagine that.

Scott

Very enlightening and can now see what I'm up against if and when I attack.
Still would like to know where the other end of that wire is and where the ECM is as well.
Just reviewed my onboard manuals and of all things, it physically shows 3 thermocouples installed, including one on the end of the dip stick...geeezzzzhhhh! One of the three is placed in the our discussed area, but again, it's called a thermocouple. No mention or physical location of the ECM, unless we're talking about the control panel in the cabin overhead cabinet. No wiring schematics or diagrams to speak of, either, except for a point to point block diagram involving this panel.

[rlgosse]

I used a pallet jack and two small hydraulic jacks to get the gen down. Put some blocking on the pallet jack and used the two small jacks to lift it slightly, remove the supports and slowly lowered it on to the pallet jack. No worry about it tipping as it is surrounded by the frame on both sides. Was cautious cause wasn't sure how the weight was distributed. Saw a neat little RV jack at Canadian tire for $170 bucks but it looked a little short so I went with what I had. Didn't seem to be much weight on the inside support bracket. Lots of extra fuel line coiled up so just cut the at clamps, inserted a piece of wood dowling in each and tightened the clamps to keep from leaking fuel. There is a return fuel line. Disconnected the batteries and shore power then disconnected 12volt and 120volt lines at generator.

Still can't get the sensor out so may have to run it in to cummins. Don't feel like tackling the head removal with out a manual, and possibly screw something else in the process.

Thanks guys for the support

[tropical36]

Originally Posted by rlgosse

I used a pallet jack and two small hydraulic jacks to get the gen down. Put some blocking on the pallet jack and used the two small jacks to lift it slightly, remove the supports and slowly lowered it on to the pallet jack. No worry about it tipping as it is surrounded by the frame on both sides. Was cautious cause wasn't sure how the weight was distributed. Saw a neat little RV jack at Canadian tire for $170 bucks but it looked a little short so I went with what I had. Didn't seem to be much weight on the inside support bracket. Lots of extra fuel line coiled up so just cut the at clamps, inserted a piece of wood dowling in each and tightened the clamps to keep from leaking fuel. There is a return fuel line. Disconnected the batteries and shore power then disconnected 12volt and 120volt lines at generator.

Still can't get the sensor out so may have to run it in to cummins. Don't feel like tackling the head removal with out a manual, and possibly screw something else in the process.

Thanks guys for the support

Sounds close to what I had in mind and do have a platform built that allows my floor jack to go in and out from under it. I used it to remove the Generac in my gas coach once. This thing weighs over 400lbs, so I wouldn't want any balance or weight distribution mistakes.
Now, could you possibly trace the wire from the sensor and tell me where it goes to and maybe give some details as to how one might get to the other end of this wire from below and without removing the genset?
Also, have you tried the heat/freeze method mentioned for removing the sensor and I assume by now it's been soaked with WD40 or other?
Keep us posted and if it ends up at Cummins, I'd be interested in knowing of the damage.

[rlgosse]

I tried heat from the propane torch and squirted movit all around with no luck. Might try one more time with the freeze trick before taking it in to cummins.

Didn't trace the sensor wire but would suspect it terminates in the multi plug disconnect. Several posts about taping a sensor to the rad hose which may be ok for very temp but as several others posted, sensor serves other functions and should be installed in the block side of the thermostat to satisfy all the functions.
Pretty easy to round off the wrench shoulders as they are brass and devider gets in the way. Using a 3/4 - 6 sided socket which seems a tad loose. 18mm is to small so I've ordered a 23/32nds. Pulling wrenches not my "long suit".

Drained antifreeze to work on unit. Will it hurt the cylinder walls to leave it dry for a week or so. Worried about corrosion starting.

[tropical36]

Originally Posted by rlgosse

I tried heat from the propane torch and squirted movit all around with no luck. Might try one more time with the freeze trick before taking it in to cummins.

Didn't trace the sensor wire but would suspect it terminates in the multi plug disconnect. Several posts about taping a sensor to the rad hose which may be ok for very temp but as several others posted, sensor serves other functions and should be installed in the block side of the thermostat to satisfy all the functions.
Pretty easy to round off the wrench shoulders as they are brass and devider gets in the way. Using a 3/4 - 6 sided socket which seems a tad loose. 18mm is to small so I've ordered a 23/32nds. Pulling wrenches not my "long suit".

Drained antifreeze to work on unit. Will it hurt the cylinder walls to leave it dry for a week or so. Worried about corrosion starting.

Can't answer the corrosion question, but would think that something like that would take awhile and especially since it didn't have just water in it.
I guess I can find this multi-plug connector for whatever it might be worth and too bad finding good electrical diagrams and schematics is like pulling hens teeth on this thing.
So, what color is the wire, if it's not too much trouble for taking a look?
With your present dilemma, I would think that replacing the whole housing would be less trouble and expense, than taking it to Cummins and can already feel sticker shock waves. Having said that, I might just end up there, with the whole coach and do need to settle down some, at this age. Might just wait until I'm traveling again and for stopping at one of the Central Camping locations.

[rlgosse]

Well guys, yaba Daba doo, thanks to the great pictures, I finally got the little beggar out.
Dropped the gen, pulled the top and thermostat, drilled a 15/16 hole in the plastic decvider used a little heat from the propane torch and a few squirts of Freeze off and out it come, minus the lower section. Heavied up on the Freeze up, punched it inside and fished it out.
Followed some of your suggestions and it worked out. Heck of a job cleaning the corrosion out of there. Had plugged the bottom of the hole but may have gotten some debris down there. Will use the vacuum tomorrow to suck it out. Anyone know if it is an open chamber throughout or should I be concerned with orfices that could get plugged. Have to flush anyway. Would you squirt a drop of electrical connection cleaner in there to clean the corrosion off the wall.

Thanks for all the helpful instructions
Bob

[rlgosse]

Well guys, yaba Daba doo, thanks to the great pictures, I finally got the little beggar out.
Dropped the gen, pulled the top and thermostat, drilled a 15/16 hole in the plastic decvider used a little heat from the propane torch and a few squirts of Freeze off and out it come, minus the lower section. Heavied up on the Freeze up, punched it inside and fished it out.
Followed some of your suggestions and it worked out. Heck of a job cleaning the corrosion out of there. Had plugged the bottom of the hole but may have gotten some debris down there. Will use the vacuum tomorrow to suck it out. Anyone know if it is an open chamber throughout or should I be concerned with orfices that could get plugged. Have to flush anyway. Would you squirt a drop of electrical connection cleaner in there to clean the corrosion off the wall.

Thanks for all the helpful instructions
Bob

[tropical36]

Originally Posted by rlgosse

Well guys, yaba Daba doo, thanks to the great pictures, I finally got the little beggar out.
Dropped the gen, pulled the top and thermostat, drilled a 15/16 hole in the plastic decvider used a little heat from the propane torch and a few squirts of Freeze off and out it come, minus the lower section. Heavied up on the Freeze up, punched it inside and fished it out.
Followed some of your suggestions and it worked out. Heck of a job cleaning the corrosion out of there. Had plugged the bottom of the hole but may have gotten some debris down there. Will use the vacuum tomorrow to suck it out. Anyone know if it is an open chamber throughout or should I be concerned with orfices that could get plugged. Have to flush anyway. Would you squirt a drop of electrical connection cleaner in there to clean the corrosion off the wall.

Thanks for all the helpful instructions
Bob

Good for you!
Again, could you tell me what color the wire is on top of the sensor, so that I might find the other end and experiment some with it?

[rlgosse]

Sorry I missed that. I think it is a white wire. Can't remember if it had a tracer on it or not. I'll check tomorrow and see if I can see where it goes.

[Carhauler]

I did Genset complete service recently, took coach to Cummins shop paid 600.00 for them to remove and replace I performed service. Replaced all hoses,pump,clamps,t stat,pump belt. By time I finished total cost was around 1100.00. Parts was around500.

[tropical36]

Originally Posted by rlgosse

Sorry I missed that. I think it is a white wire. Can't remember if it had a tracer on it or not. I'll check tomorrow and see if I can see where it goes.

Thanks and have since seen that in some videos.
Also appears that it's in the bundle with a connector on the firewall and going up to the control center in the cockpit.
Please confirm if you can.
Still with all this info, it looks like I'll still be going the regular route of having to pull the genset and will do so, once my help becomes available.

[rlgosse]

So the 7.5 is all back together and remounted in the 05 Expedition.
Replaced the temp sensor, belt, thermostat, rad cap flushed and refilled with Fleetguard 50/50. Cost about $250 Canadian.

Many many thanks to all for the helpful posts eapecially to Fireup for the great pictures and Tripical36. The heat and Freeze up trick was especially appreciated.
Could probable do it in 1/4 of the time now. Wouldn't take a lot of thought to out do a bunch of that engineering.

Happy Motoring
Bob