Onan 7500QD Gremlins

smlranger wrote:
If you decide to get inside the generator to R/R the temp sensor, just heat it a little bit with a propane torch, then spray it with some good penetrating spray (I used Deep Creep) and it will come out easily.

Also, at 3,000 hours, if you already have it apart, I would replace the belt, coolant hoses, the T stat, adjust the valves, and get the radiator cleaned and checked.

Hey SML,
Ha! yeah sure that little sensor will "come out easily". As you can see in the pics, mine was fighting me 'till the last thread. I used everything in the book to get it out. And, as you can see, it broke off in the efforts. And yes, that was with heat and penetrating oil, (several brands)too. The straw that broke the camels back was, a little trick I thought up but, was skeptical.

I purchased a can of "Freeze" from a place called "Marshalls" on Miramar road in San Diego. It's like a smaller sized Home Depot, lowes, ACE Hardware, and Tractor Supply, all rolled up into one store but, only on a smaller platform. They had this stuff called Freeze.

I bought some, buzzed home and, heated the area around the stub that was left from me using Gorilla efforts to get that sensor out and, when it was thoroughly heated, I sprayed this "Freeze" right on the left-over stubble. I then grabbed it with my smaller pair of Vice grips and, out it came. Whew!!!!!! That was one tough little bugger.

But, you can see why it was so tough. It was completely corroded all the way around those threads which, locked that sensor into position and, was not going to let it go.

I failed to mention earlier that, in the onset of my gorilla efforts, I put so much torque onto that little sensor that, I cracked the lower T-stat housing and, didn't know it. So, I got it out, cleaned up the threads with a tap, installed the new sensor, replaced each and every part of that generator with the exception of the outer panels and, started filling it with antifreeze.

DRIP, DRIP, DRIP, DRIP, DRIP....... What the he..... is this? I checked and re-checked all my brand new clamps, hose ends and everything else that had anything to do with the cooling system and, NOTHING. But the drips, actually a small, steady stream of Antifreeze was dripping out the bottom of the unit.

So, in comes my mirror on a stick. Whaaaaaaaaaaaaaaat is this? Low and behold, it's a CRACK in the lower T-stat housing that's impossible to see, without the use of a mirror.

So, on the phone to Cummins/Onan and, ordered up some parts, including a head gasket 'cause the only way to replace that little, lower T-stat was to remove the head!!!!!!!!!! Oh well, all in a days work.
Scott

P.S. Below is a pic of that lower T-stat housing. You can see the crack in the lower section of it.