8N Overheating - Spitting coolant out and steam coming out

MOmilkman

Member
I have a 8N. I think 48. Not sure of the year.

Symptom: Spitting steam and coolant out from under the cap only when under a load. In my case PTO is engaged and using a finishing mower.

Before this started I recently removed the front mount distributor and thoroughly examined it. Rear brass bushing had small amount of play so I sent it out to a machine shop and had it replaced. Installed a new Dist shaft, set timing on the bench and put it back on. Don't know if this is in any way related but I thought it worth mentioning.

So far to try to rectify the steaming issue I have put a new thermostat in (never had one)(put the pointed end toward the radiator).
Sprayed the debris out of the radiator fins (spraying from the fan side toward the front.
Drained the radiator and back flushed it from the lower hose out the top hose.
Ive kept the level of the fluid just above the core.

All of this has done little to nothing for me and it has a noticeable loss in power than before. It idles and runs fine, but less power.

Kinda at a loss. Been working on it all summer and my little Craftsman lawn garden tractor is gonna puke on me sooner or later. its been doing the bulk of the 5 acres all summer.

Any suggestions, Im all ears. I'll try anything.

p.s. I changed the cap to a ornamental one a while back but I cant remember why. I think because at that time I was filling it too full and thought the cap needed replacement when in fact I was just filling it up to much.

Thanks
 
Head gasket.

If you can make it do it by loading up the engine
(like with the rotary mower or up a steep hill) you
are getting exhaust gasses/cylinder pressure in the
radiator. Been there done that about 35 years ago.
 
(quoted from post at 20:17:07 08/21/16) Head gasket.

If you can make it do it by loading up the engine
(like with the rotary mower or up a steep hill) you
are getting exhaust gasses/cylinder pressure in the
radiator. Been there done that about 35 years ago.

Interesting take notjustair. Not one that I wanted to hear but none the less useful info. Thank you
 
Fill the radiator clear to the VERY top and crank up the engine. If bubbles appear you have a failed head gasket or crack in the head
or cylinder wall.
 
(quoted from post at 06:43:01 08/22/16) Fill the radiator clear to the VERY top and crank up the engine. If bubbles appear you have a failed head gasket or crack in the head
or cylinder wall.

I've heard of doing that before but had forgot about that. Good idea. However, it would be hard to diagnose in that manner considering I just filled the radiator back up last night after back flushing it. So I'm going to pockets of air escaping for a while. I'll have to run it for a bit to get the pockets of air out then try it I suppose.
 

If you suspect sediment and Scale are the cause of the over-heating, I sure would knock out a couple "Freeze-Plugs" at the lower part of the engine Block and flush and Prod around to be SURE it is clean...

No telling how much could be piled up in the Block...
 
Easiest engine in the world to do a head
gasket, no valves, pushrods etc to play
with just unbolt clean and replace. Can
be done in an afternoon
 
I'd do that before I'd troubleshoot a head gasket problem.

You can also look for a "clean" plug (as in steam cleaned) or white smoke in the exhaust. Sometimes a compression test will detect a head gasket problem if it's bad enough. And, usually, a head gasket will cause performance problems.

You can run all of these tests or just do a leak down test & cut to the chase.
75 Tips
 

I thought about a leak down test before but haven't done it yet. I went and bought a infrared thermometer today. Gonna check the radiator and block and see what the temps show.
 

A leak down test my not show a leaking head gasket and a compression test may not either. He needs to pressurize the cylinders @ 100 PSI to find a borderline leaking head gasket.

http://forums.yesterdaystractors.com/viewtopic.php?t=1191074&highlight=black

A combustion gas leak test more than likely will show it up but he would have to buy a tool to do it.

https://www.napaonline.com/napa/en/p/BK_7001006/

https://www.youtube.com/watch?v=B4FoUc6fRNs

https://www.youtube.com/watch?v=uVn-IDi7da8
 
MOmilkman,If it is a 48 engine check your timing with a timing light at the flywheel timing hole, 4? BTDC Initial Timing @ 500 rpm.Advance @ 2000 RPM 18? points set @.015.If the timing is off it can cause your engine to over heat.
 

I believe mine to be a 48 but not sure. It is a front mount distributior. Do you have any way of taking a picture and showing me where the timing hole is?
 
No it did not. I have been told by several people that having the timing off does not affect overheating. I don't know what to believe.
 
(quoted from post at 17:29:57 08/24/16) No it did not. I have been told by several people that having the timing off does not affect overheating. I don't know what to believe.
ront mount distributor engines do not have the timing hole . I guarantee you that retarded enough timing will cause overheating!
 
" I have been told by several people that having the timing off does not affect overheating."

They're wrong.

Pull the distributor. The first thing you need to check is bushing wear. If the shaft has any sideways movement AT ALL, the bushings must be replaced. (see below)

Look at the old points; are they burned, pitted or misaligned? Check the point gap, .015 on all four lobes. Make sure the blade is at a perfect right angle to the points. You want to feel just the slightest bit of drag when you pull the blade through the points. Set the points on the high side of the cam and ensure they align correctly. Make sure you have the star washers under the screws on the points. If you need to replace the 8-32 X .19 fillister head screws, ensure that the new screws do not interfere with the advance weights. Dress the points by running a piece of card stock or a brown paper bag through them. New points sometimes have an anti-corrosive dielectric coating on them & old points can corrode or pick up grease from a dirty feeler gauge or excessive cam lubricant. And, don?t forget to lube the rubbing block w/ cam lube; not Vaseline, not bearing grease, but cam lube (** see below).

If you are using quality points and cannot get the gap to open to .015, chances are you need to replace the bushings.

Now, set the timing. Get a meter or test light, a 21/64? drill bit (*** see below) & a metal straight edge. Put the distributor face down w/ the condenser on the left & the timing plate lock screw on the bottom. Look at the end of the shaft: it has a narrow side & a wide side. Make sure you can tell the difference. Now, place the drill bit in the bottom mounting hole (this will be your reference point for measuring). Next, place a straight edge on the wide side of the tang on the shaft as shown in fig. FO83 in the picture. Rotate the shaft CCW (as viewed from rotor side OR CW as viewed from back/tang side) until the straight edge is ?" beyond the outside edge of the drill bit you stuck in the distributor mounting hole. At this distance, the distributor points should start to open (get your meter/light out now & check). If not, loosen the timing plate lock screw and turn to advance or retard the timing (move the plate down to advance timing, up to retard). Remember, each one of those little hash marks represents about 4? of timing. Keep adjusting until you get the proper ?" setting. (if the plate won?t move, you might need to remove the big C clip to loosen it a bit) As you?re adjusting, eliminate backlash by turning the shaft backwards (CW as viewed from the front) and bring the shaft forward (CCW as viewed from the front) to measure your setting. This ?" setting will get you static timing at top dead center.


* NAPA part numbers:

?Points: FD-6769X
?Condenser: FD-71
?Rotor: FD-104
?Cap: FD-126

** Distributor cam lube:

http://www.napaonline.com/Catalog/Result.aspx?Ntt=ECH+ML1&Ntk=Keyword&Nty=1&Dn=0&D=ECH+ML1&Dk=1&Dp=3&N=0

** Distributor cam lube
http://www.carquest.com/webapp/wcs/stores/servlet/subcategory__10151_-1_10651_11340


*** Rather than the drill bit, a jig made by Dan Allen (The Old Hokie) will make this task quicker & more accurate
75 Tips
 

So based on that information I'm about 99% sure that my tractor is over heating solely because my timing is off or something related to the distributior because it started the day I put the distributior back on. Thanks for your help.
 

Bruce,
The first thing I CAN tell you is that my bushings are fine. When I replaced the shaft I checked those and the rear one was a touch loose so I had it replaced. The front is fine.

I'm not so sure about the points or the timing. I sincerely appreciate the info and am going to go though everything again when I get time. I'll just have to revisit this thread over and over until I've covered everything and if all that fails I'll come back for more possible guidance.

Thanks guys.
 
Since you problem recently raised its ugly head, this is not likely the cause or solution, but may help someone. On an N that I have worked on over several year period, one thing or another, it would overheat. Cleaned radiator, replaced water pump, added shroud, flushed many times and a few with vinegar (insanity=trying same thing over & over expecting different result), rodded radiator, verified temperature gauge, flushed block & radiator separately, and finally examined radiator cap. It was wrong one! See sketch. The spring & lower seal was too short to reach & seal at the lower seal point in radiator neck, so it was running unpressurized. Personally, my 8N works fine unpressurized, but apparently all do not (guess some need that extra 12 degrees that come with 4PSI), as this one now has about 10 hours on it with out overheat/ boil-over when mowing at over 90 outdoor temp. Will this be a permanent solution, only time will tell. Hope so, because owner & myself are really very tired messing with it! All radiator caps may look alike but there are not.
 

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