Onan temp sensor oops

[HD4Mark]

While attempting to replace the coolant temperature sender or sensor the old one disintegrated inside the housing. Now the outside brass from the old one is stuck inside so the new one will not fit in. I have remove the thermostat to try to get at it from the top but the sender housing angles up so the only good that does it to be able to retrieve it if it pushes through.

I am considering trying to make an alternate mounting for the new one possibly inline in the radiator hose then screwing the old one back in the housing with some teflon tape or pipe dope to seal off the old and abandon it. Ideas appreciated.

EDIT: The genny is a quiet diesel 7500 HDJAK

[HD4Mark]

After removing the thermostat and top of it's housing I took a bolt and tried to beat the piece inward. It moved a little so then using a bent rod and some 90° long nose pliers I tapped in out from the inside. Plenty of PB Blaster helped.

Off tomorrow for some antifreeze to fill it back up and trial run. Wish me luck.

[FIRE UP]

HD4Mark,
Welcome to the world of seriously stubborn Onan Temp Sensor removal. Some of us have been in the same boat and others have been a lot more lucky and theirs walked right out without issue. I put so much torque on that little sensor that I tweaked and cracked the lower thermostat housing and didn't know it 'till I started filling the system with anti-freeze and it was running out and I couldn't see from where.

Well, needless to say, I had some work ahead of me to replace that lower T-stat housing. But, that's another story. I'm not sure of where you plan on an alternate location for that little guy but, it needs to be very close t the thermostat so it can send the correct info to the engine ECM. Anyway, good luck with your repair, been there done that.
Scott

[HD4Mark]

Originally Posted by FIRE UP

HD4Mark,
Welcome to the world of seriously stubborn Onan Temp Sensor removal. Some of us have been in the same boat and others have been a lot more lucky and theirs walked right out without issue. I put so much torque on that little sensor that I tweaked and cracked the lower thermostat housing and didn't know it 'till I started filling the system with anti-freeze and it was running out and I couldn't see from where.

Well, needless to say, I had some work ahead of me to replace that lower T-stat housing. But, that's another story. I'm not sure of where you plan on an alternate location for that little guy but, it needs to be very close t the thermostat so it can send the correct info to the engine ECM. Anyway, good luck with your repair, been there done that.
Scott

Thanks Scott,
I am hoping I did not crack the housing We will see tomorrow. The only thing I could think of to relocate it was to cut the radiator hose on the top near the thermostat and put in a piece of pipe with whatever size threaded female bushing either a T or soldered. This idea of course was in between choice swear words after the thing fell apart.

How did you replace the housing? Could you do it by crawling under and working from the rear (actually the right side of the gen) or did you have to remove the whole thing? If mine is cracked I will likely be in the looney bin after having a fit in my driveway.

[FIRE UP]

Originally Posted by HD4Mark

Thanks Scott,
I am hoping I did not crack the housing We will see tomorrow. The only thing I could think of to relocate it was to cut the radiator hose on the top near the thermostat and put in a piece of pipe with whatever size threaded female bushing either a T or soldered. This idea of course was in between choice swear words after the thing fell apart.

How did you replace the housing? Could you do it by crawling under and working from the rear (actually the right side of the gen) or did you have to remove the whole thing? If mine is cracked I will likely be in the looney bin after having a fit in my driveway.

HD4Mark,
Sorry for the late reply. Anyway, knowing what I know about those sensors, and, if I had to do it all over again and, the sensor even closely started to give me trouble in removing it, I'd do EXACTLY what you're thinking of, and that would be to install some tubing, the exact size that the radiator hose would fit and, install a "bung" of what I think is 3/8" pipe threads into that piece of tubing. I'm sending along a picture of a similar situation on the bottom side of our engine (The CAT C-7, not the engine for the generator) in which Freightliner, in its infinite wisdom, "hid" the pet cock for the rear radiator. So, draining it for removal of the radiator was a serious pain in the a$$.

So, the cross tube, that travels right under the front section of the oil pan is steel. I drilled a hole, brazed in a bung, and installed a pet cock for the next time I need to drain the cooling system. Why Freightliner could not do something like that, I'll never know.

Anyway, you asked about the removal of the lower T-Stat housing if, you should break it or, it will not house the sensor due to destroyed threads or any other reason for non-continued use. Well Partner, you've got two choices.

Because Kubota, in IT'S INFINTE WISDOM, placed that lower thermostat housing on the engine in such a manor that the bolts on it cannot be removed completely without extensive work, here's your choices.

1. Remove the entire front of the engine (fan belt end) and all related hardware and equipment that's needed to be removed to gain access to that T-Stat housing.

2. (to me, a lot easier) Remove the CYLINDER HEAD of that little Kubota. In all reality, from the time I put my first tool on the engine to remove the head, 'till the time that little head was on my work bench, was right at 45 minutes. And I'm no speed mechanic, I take lots of breaks. But, in reality, it's way easier to remove that head than the front of the engine.

All that's needed to re-install it was a head gasket. No big deal. I But, it sure made removing that lower T-Stat housing very easy. By the way, Onan does not refer to it as T-stat housing. They call it a water pump bracket, huh?? Oh well, it was about $52.00 from Cummins/Onan, the head gasket was $46.00 and the sensor, about $17.00.

Anyway, hope this info helps some. If not, PM me and I'd be glad to help with your situation from this end.
Scott

[HD4Mark]

Good news Scott, After fighting with it and getting the rest of the sender out I topped up the antifreeze, crossed my fingers and (pun intended) fired it up. No leaks, no shut down and no error codes. Ran it for 1/2 hour or so with the a/c on no problems. Hours later tried it again, still OK.

I am starting to think that every year or two the sender should be removed and if not replaced just broken loose to make sure we don't have this problem.

[FIRE UP]

Originally Posted by HD4Mark

Good news Scott, After fighting with it and getting the rest of the sender out I topped up the antifreeze, crossed my fingers and (pun intended) fired it up. No leaks, no shut down and no error codes. Ran it for 1/2 hour or so with the a/c on no problems. Hours later tried it again, still OK.

I am starting to think that every year or two the sender should be removed and if not replaced just broken loose to make sure we don't have this problem.

Mark,
Roger that Sir, a "periodic" R&R of that sensor just might keep it from developing the "locked up" scenario that you, me and many others have had to deal with. So, glad you did it right and, it's working as should.
Scott

[teddyu]

A good addition to the fixes is the use of never-seize on the threads. Acts similar to pipe dope and, I think, is better than teflon tape. Proper torquing is also a must. JM2¢...

[HD4Mark]

Originally Posted by teddyu

A good addition to the fixes is the use of never-seize on the threads. Acts similar to pipe dope and, I think, is better than teflon tape. Proper torquing is also a must. JM2¢...

Ouch! Too late already used teflon tape. I figured it would be better than pipe dope that I would normally use. Torque wise I'm sure my service manual has specs but I just cranked it lightly, tight but no gorilla.

The good side to this genny is it can tell you what is ailing it. The bad side is you seem to need that too often

[Greg2]

I know not of the specific generator giving problems, but after looking at the pictures, is not the brass fitting it screws into available? If it is and also reasonable priced, I would think that after a certain number of swear words if it were mine, I would get a new fitting, screw the new sensor in it and replace it in the gen.
Certainly would be better that spending a lot of unproductive time trying to get the old sensor out. YMMV.

[FIRE UP]

Originally Posted by Greg2

I know not of the specific generator giving problems, but after looking at the pictures, is not the brass fitting it screws into available? If it is and also reasonable priced, I would think that after a certain number of swear words if it were mine, I would get a new fitting, screw the new sensor in it and replace it in the gen.
Certainly would be better that spending a lot of unproductive time trying to get the old sensor out. YMMV.

Greg2,
Well Sir, I think you might be mis-interpreting the pictures. The sensor is brass but, the housing where it lives is aluminum. There "NO" brass fitting that the sensor screws into and then, is inserted into the housing. And spending "unproductive" time is what's required in many of the sensor removals in these particular generators. As stated earlier, some of them "walk" right out right out without issue. But, some, as you seen in mine and the OPs, fought us for the entire amount of the removal process.

A metallurgist and or a chemist may be able to defend why that sensor sort of "seizes" up in some of them, but not all. My anti-freeze in that gen was absolutely flawless, green and clear as it could be. And, the every inch of the interior cooling jackets that I could get my eyes on, looks spotless with the exception of the surrounding area of that little sensor. As you can see, it looked like that cooling system was decades and thousands and thousands of hours old and, had never been maintenanced.

At the time those pictures were taken and, I was having the "Code 33" issue(s) that 7.5QD Onan only had "105" hours on it. So, after coaching many folks through a repair, just like the OP has done, there is no rhyme or reason as to when and why, these model gens develop that issue.
Scott

[HD4Mark]

Originally Posted by Greg2

I know not of the specific generator giving problems, but after looking at the pictures, is not the brass fitting it screws into available? If it is and also reasonable priced, I would think that after a certain number of swear words if it were mine, I would get a new fitting, screw the new sensor in it and replace it in the gen.
Certainly would be better that spending a lot of unproductive time trying to get the old sensor out. YMMV.

The sender is a one piece, looks like brass to me, part that screws into a tapped 45° hole in the thermostat housing that appears to be aluminum. Dissimilar metals. It fell apart while trying to get it out. By looking I would guess that the reason they are so hard to remove is due to corrosion building up around the end of the sender not so much on the threads.

Now that it is running I plan a flush and fill of the system to try to prevent some of the corrosion.

EDIT: Scott snuck that in while I was typing so this is a little redundant.

[FIRE UP]

UOTE=HD4Mark;1757836]The sender is a one piece, looks like brass to me, part that screws into a tapped 45° hole in the thermostat housing that appears to be aluminum. Dissimilar metals. It fell apart while trying to get it out. By looking I would guess that the reason they are so hard to remove is due to corrosion building up around the end of the sender not so much on the threads.

Now that it is running I plan a flush and fill of the system to try to prevent some of the corrosion.

EDIT: Scott snuck that in while I was typing so this is a little redundant.[/QUOTE]

That happens to me too Mark, I'm answering someone and another poster many times, puts in the same or, close to the same answer I was typing in. Oh well, no biggie. But, what I was going to tell you Mark is, flushing most likely will not do any good. The reason is, if you studied that sender, the new one not the old one since it was disintegrated, and looked carefully at the actual probe on the end, then, looking at the actual bore in the thermostat housing that it resides in, you'd notice that there's vary little clearance between the two components even when both are new.

Well, being positioned where the two are, in the cooling system, and coupled with the fact that there's very close tolerance in between the two, what happens is, there's very little VELOCITY of coolant flow in and around that probe. So, the potential for the build up of corrosion for that tiny clearance area is high. Now, I'm not saying that flushing won't do any good at all. In fact, I hope it does. How are we to tell, the only way is to painstakingly remove that sensor, about once a year, plus or minus to see what kind of progress the corrosion has or, if any at all.

Not many are willing to do that. Especially the ones that don't have their gen on a sliding tray, like ours. So, give your maintenance its best shot and hope for the best.
Scott

[donwat91]

HD4MARK, if only mine was put on a slide I could have saved me a lot of money. I just got mine out of the shop about 2 weeks ago for the same reason. Fault code 33., Failed temp. Sensor. Cummins/Onan did the work at the cost of $2112.62. The only thing different was the radiator was stopped up and instead of waiting for them to send it out to be repaired I had them put a new one in. Thats the only difference. The labor was $1569.00 . Most of that labor was taking it out and putting it back in. If only they had be it on a slide !!!!! Thanks for listening to my cry. Lol
Donald"Dr.Don"Watkins
MSgt USAF Ret