706

[shade tree operator]

Last year my neighbor's 706 gas(263)started running hot while mowing with a 5'rear mower. I put in a new thermostat, but no fix. Next, the radiator was taken to a shop , boiled out and pressure -checked, but still overheated. Put an after-market temp. gage to see if the factory was accurate. The factory gage showed much hotter so I left the after-market one on, but the engine still ran hot. Checked the rad. cap , but changed it anyway. Still would overheat enough to blow coolant out of the over-flow on rad. This past winter, I took the head off and expected to find a cracked or warped head. Took the head to a machine shop where it was cleaned, magna-fluxed and machined level again(took 14 thousands off to clean it up). Took the water pump apart to make sure the impeller was tight on the shaft, and it was.(Saw one get loose on a small-block chev. years ago). Put the head and water pump back on and ran 5 gal. of gas through it mostly at high idle, and it never got much over 190 degrees, so I thought the thing was fixed. Wrong. Neighbor got back from wintering in Texas, drove his tractor three miles home and it overheated again. Tried another new thermostat,no good.Took off lower rad. hose and flushed with garden hose(clean),knocked out front and rear freeze plugs and water jacket was clean as well. Since this has all started, I have looked for coolant in the oil several times but have found none. Can someone please tell what I am missing?

 

[pete 23]

I would pressure test each cylinder for comb leak. Exact top dead center on each cyl on comp stroke and hook up cyl leak down tester. Or, quick and easy test, fill radiator as full as it will go, remove belt from water pump, start engine, rev it up and down to put max combustion pressures in cyl and coolant should not move in radiator. If it does in the first 30 seconds or so you have comb leak. Not unusual to leak where head gasket crosses the sleeve flange if sleeve flange is a little too high.

 

[the tractor vet]

First off put a timing light on it and set the timeing at 23 degrees BTDC at full throttle check and make sure the centricial advance is working . Next change the gas and move up to 93 octane . If that does not help a ton then i will have to thing on it a little more.

 

[pete 23]

Some times I get a little ahead of myself and jump to more complex solutions. I would indeed check the timing like the Vet says. So many guys time these tractors at low idle speed which is rather unimportant. It is the high idle timing that counts as that is where you are going to be loading them at. If you run at throttled back part way that is when the advance curve and condition of the advance mechanism becomes even more important. IH used to include a new distributor with the original sleeve and piston updating packages on these engines as they changed the total advance and curve . Originally they had a 25 degree advance but you were still supposed to set timing at 22 degrees btdc at full throttle, then they went to a 22 degree shaft with corresponding springs to match.