I removed the shot thermostat from my D2 5U engine and noticed it looked an awful lot like the ones I took from a D7 3T engine. Neither has any part number that matches either the 3T book or the 5U book.

Thermostat on the left is from the 3T. It is stamped C640 and 353.

One on the right is from the 5U and is stamped MoToRsTaT, patent numbers from the 20's, Mfgr name and numbers 7 and 48.

Neither indicates an opening temperature. The D7 thermostat fits just fine.

Question: Is the opening temp on the D7 thermostat close enough for the D2 engine?

These suckers have enough brass in them to cast a buffalo. I sure don't want to fork over for a new one if one of these will work.

Thanks,

Jack

The one on the left is a Cat thermostat and the one on the right looks like an aftermarket one.It,s been so long since I checked the opening temp. on them but it comes to mind they opened in the lower to middle 170s but not sure.It seems all the later ones opened fully at 180 degrees if I recall.That D7 thermo. should work just fine in it as most all the Cats used that same one (type) back then.Wouldn,t hurt just to put it in some water and heat it and check the temp. and when it opens just to make sure it,s good yet. This isn,t prertaining tothe tractors but over the years I found for cars and pickups or gas engines that the Robertshaw thermostats were the very best in my opinion. They were always available at the NAPA Automotive Stores and presume they are yet but I haven,t bought any for quite awhile now.

The early D2's, 4's, 6's, & 7's all used the same 6F9467 regulator.
Operating range 166-170 deg. F. Fully open at 183 deg. F.
(Early being the "U" models and the 3T plus others, not the very early units)

Attached instructions to dismantle and clean.

Thanks to both. Next step--boil some water and see what it does. Both units look good and close off. (they also look expensive!)

Jack

I may not have it right but I seem to recall about $90.

Nothing wrong with using automotive type thermostats....a whole lot cheaper but you will have to machine up an adapter ring......and if you do that go for an arrangement that doesn't use that pressed in collar.

The thermostat for a D-2 " U " series is old part #4F7059... now changed to new part #6F9467..... the last one I bought from Cat was in 2007 and cost $ 39.34. It was also availible at NAPA for a little more money.

Thanks Wayne,
Now that you've jogged my memory, I was thinking "pair" for the D6:)
Pricing anything these days is pretty scary.

Yes, that brass collar was a bear to get loose. i hammered out a little slide hammer puller that got them loose after a lot of tap-tap-tap and a lot of PowerLube. I got to pull three of them this morning.

I'm thinking of machining about 0.003" off that ring and holding the ring down with the dome, since I have to fabricate a special dome for my application anyway, all part of the co-generation system I'm building. At the very least it will get a good coating of anti-sieze.

Cat had a special puller to pull that ring out and we had one at the dealer so was real easy to pull it out. They had the two puller legs on it and a bolt in each leg to get it out so was easy with it to pull the ring. I never tried to pry the ring out but I am sure it was a little problem to do it that way but I guess not impossible. A slide hammer would be better than a pry bar.

Jack,

When I took mine out for replacement it was a bear to get out, even after I made a puller. The ring got distored to the point I wasn't sure how it was going to work. The new CAT thermostat had a thicker flange than the one I took out, so I machined the ring true to accomodate the thicker flange. I tested the old one I took out and it was partially stuck open. A little cleaning and it worked OK, now have a spare. Sound like your making progress.