Some of you have been following and commenting on my "Code 33" thread for my Onan 7.5 Quiet Diesel gen problem. Well, as many of you know, there's many possible remedies for that code. I checked all the obvious ones, like clogged air intake, low coolant, low oil, obstructions in any portion of the air flow/radiator cleanliness and much more. It's all perfect inside that big green box.
I have a kink in the hose from the overflow tank to the bottom of the radiator but, have un-kinked it at different intervals and it makes no difference at all. So, I figured, if I have to get into it mechanically, I'll start with the temp sensor. That apparently has been an issue of at least some of these models.
Well, as you can see by the pics, the temp sensor is installed just below the thermostat, in the lower half of the thermostat's two housings. It has somewhat, close proximity to the shroud (called bulkhead in tech terms in the manual) so, getting a good bite on it from a wrench or any form of socket was almost impossible. I've had that situation so many times where you can see a nut or bolt as clear as day but, can't get a tool on it or, can't get your fingers on it.
So, I broke out the stubby 3/4" combo wrench and got it to fit on that sensor with just enough swing left to break it loose before the wrench OR MY KNUCKLES would hit something immovable. Well, the wrench started to move but, the sensor wasn't. I took another bite just to make sure it was aligned up just right on the sensor. The wrench moved until it hit the shroud.
As I removed the wrench, I could see the rounded points of the sensor so, a wrench and or socket, from this point on, is useless. So, out came the venerable "Vice Grips". I could barely get them on that sensor due to the tight quarters. Guess what, they started slipping too. Huh??? Well, it's time for the gorilla grip on the vice grips. I took hold of that sensor, tightened the adjustment on the vice grips and squeezed the heck out of them to clamp them onto the sensor.
This ought to do it. SNAP! Off came the sensor head! GREAT! Now what have I done?? So, a few choice words, and I just about had to retrieve the vice grips stuck in the fence, and go at it again. All it's doing is slipping. MAN, this thing is in there tight. So, the next step is the "PIPE WRENCH". Well I managed to get it on what was left of the sensor and guess what, it slipped just like it was lubed up with grease.
Apparently, the two metals, brass and aluminum have basically seized and fused together. Well, as you can see in the pics, I don't really have a lot of options here.
Option 1. (preferred) Get out the dremel (with small saw rotary saw blade attached, and cut that shroud (bulk head) in such a manner that it will allow clearance for me to flush cut the remaining portion of the sensor and then, start the procedure for drilling and tapping for a new sensor. Even with this approach, I'm limited in space due to the mufflers being just behind that shroud. So, I've got to calculate whether or not I can even get the drill, tap etc. in there to do the job.
The lower portion of the thermostat housing IS removeable. That, would be a serious blessing. BUT, AND IT'S A HUGE BUT!!!!!,,, There's one bolt that cannot be removed and or re-installed until at least some of the frontal engine components are removed. Nice move Kubota!!
And, you can't get to the front of the engine unless, yep, you guessed it, the entire generator has to be removed and all the sides, sheet metal has to be removed and who knows what else???
So, as usual for me, a job that should take, oh say, around 20 minutes to a half hour, (includes break time for a nap while draining the anti-freeze) is now going to take a few days. If any of you reading this thread have also read the "Code 33" thread, you'll know I've got Three issues with this gen. One, the issue just described, two, one of the eight rotor portions (magnets) has disintegrated into a bunch of smaller magnetic pieces that were stuck to multiple metal surfaces all around the inside of that gen area. So, I need a rotor too.
And three, the gen in cold weather, cranks before the glow plugs are allowed to warm up. There is a chart that says how long the start button should be held while the glow plugs are warming up BEFORE, the engine is allowed to crank. Mine just cranks right off the bat, even when it's real cold outside and the gen hasn't been started in a long while.
So, sorry for the novel here, I just wanted to let folks know, that if they EVER intend on replacing that sensor, A SIMPLE JOB, just be prepared for what I encountered.
Called Cummins-Onan for part numbers and costs:
Lower thermostat housing (in case I can't drill and tap the old one) is $52.00
Gaskets for the removed parts $2.93 and $3.50
Rotor, are you sitting down, $467.00
So, for a grand total of around $543.00 (not including tax and any other broken parts that WILL happen when I disassemble this thing to do the repairs) I have my work cut out for me. Again, sorry for the long length but, just showing what a small project can turn into.
Sorry to see the troubles your going through, last summer my onan 7500 had sort of the same troubles. my idle would hunt a little before it stalled. I was close to a cummins power shop and went in to get it fixed. It cost me over 2500.00 when I went on my way to complete my vacation, only problem was it did the same thing the next day. In our return trip home i stopped back in and they worked another day on it and said they still weren't sure the exact problem. I had to get back to work and could not remain over a thousand miles away from home while they fixed it so we worked out how much they reinbursed me and I went home.
When I returned to the farm I pulled it into the shop and dug into it, What it turned out to be was the hard fuel lines leading to the generator had rusted and craked a very little and were sucking air. A very simple fix and cost next to nothing.
I didn't know that you were going to remove the sensor, otherwise I would've said:
What I did was to carefully figure out the exact location for a hole that I drilled in the plastic baffle/shield that's between the mufflers and the engine, such that I could use a six-point socket with a long extension and 1/2" impact wrench. This, AFTER I had applied Liquid Wrench(overnight) and had also applied a few light hammer blows on the outside of the threads(backed up with another hammer on the other side of the threaded boss). But, as you can see I had better access, as I was able to remove the sheet metal panel on the water pump side of the engine.
I was able to unscrew the brass body of the sensor, BUT it broke internally. And, I had to figure out the exact size of drill bit to drill out the broken piece(without messing up the housing).
Also, as you can see I tapped pipe threads in that access hole, and plugged it with a plastic pipe plug.
Willie & Betty Sue
Miko & Sparky
2003 41 ft Dutch Star Diesel Pusher/Spartan
Blazer toad & Ranger bassboat
Just get the whole thing out first. Use heat to get it loose. A little propane torch would probably do. It's cast so be careful about cooling it too fast. Be sure and replace the thermostat, which could have been the whole problem anyway. If the thermostat sticks in the open position the engine will get hot because the water flows through the radiator too fast to cool.