50 8N overheating

[SlowCredit]

Have fired the parts cannon and am stuck.

Ran great last two years - this year overheats after running only 5-10 minutes - load makes no difference.

Have installed new water pump, hoses, belt, radiator and felpro head gasket. No love - still boils over after 5-10 min.

Definitely overheating - pulled thermostat to be sure. Water/coolant only to top of coils. Hoses not collapsing - running
it off a bottle - have hood off (after removing/installing about a dozen times...). No shroud, but it's never had one.

Changed oil after gasket - oil looks fine - no coolant.

Cylinder heads didn't look particularlly steam cleaned - old gasket was worn out, but no obvious failure points.

If I start it without cap, I do see some bubbling after a few minutes - then eventually overflow after 5-10.


Warped/cracked head? Not thinking cracked block, as oil is fine - Maybe timing, but runs great and nothing changed from
past 2 seasons. . .

Need to mow. Any/all help appreciated!

Thanks!

Slow

 

[Bruce (VA)]

The most common reason for an N to over heat is over filling the radiator. Only add enough fluid to cover the core. (check out tip # 24, below as well as tips 25 & 35) It is not actually over heating; it is just spewing out the excess water.

If the radiator is not overfilled, check for low coolant, a loose fan belt, debris in the radiator fins or a stuck thermostat. A bad water pump will usually squeak or leak. (If you ever have a water pump start leaking or making noise, replace it immediately. A N water pump will come apart & launch the fan into the radiator.) And, unless you have a new/rebuilt water pump from a reputable source, it could have impeller erosion. The pump will turn, it wont leak, but it isnt circulating water.

In order to have a stuck thermostat, you need to have one installed. Squeeze the top hose; if it has a t-stat, you can feel it. Sometimes (rarely) the t-stat can migrate in the hose & get stuck closed. Or, in an attempt to keep that from happening, some owners will put a third clamp on the hose & tighten it too much resulting in a stuck t-stat. The OEM top hose came w/ a non-adjustable ban to keep the t-stat in place.

The fan belt should have 1/2 of flex at the mid-point; no more, no less.

Unless you have a pusher fan, blowing out the radiator from the engine side is always a good idea.

If none of that works, you may need to flush the radiator & block.

Get a can/bottle of cleaner from the parts store.

Remove the t-stat from the top hose. Reconnect the hose.

Pour the cleaner in the radiator & run the tractor to operating temp.

Then, remove the bottom hose from the radiator, stuff a rag in the bottom radiator hose connection, & stick your garden hose in the top of the radiator. Turn the water on (reverse flush) & the water will flow into the radiator, then the block & out of the disconnected lower hose. Let it run until the water is clear. Then, check the radiator flow. Stick the hose in the top of the radiator; the water should flow out of the bottom w/o backing up in the filler neck. It should flow at 19.5 gallons a minute. Dont forget to put the t-stat back in correctly!

Use 50/50 anti-freeze & distilled water as your coolant. The anti-freeze contains rust inhibitors, pump lubricant & raises the boiling point of the coolant.

If you do need to get the radiator re-cored, make sure you get the flat fin industrial core. Automotive style cores will clog up w/ debris very quickly.
75 Tips

 

[Papillon]

If it were me, I would get this: Lisle 75500 Combustion Leak Detector.

I think you are getting combustion gases injected into the coolant.

 

[Jim L WA]

Hi SlowCredit, welcome. Bruce (VA) is one of our top advisors on here, but it doesn't look like he read your post very thoroughly. I would go with what Papillon suggested.
You might be able to rent one of those testers at an auto supply store.
You may be right about the head.

 

[jimtrs]

With what you said, especially this:

[b:3c545555a8][i:3c545555a8][u:3c545555a8]Need to mow[/u:3c545555a8][/i:3c545555a8][/b:3c545555a8]. Any/all help appreciated

Check that your radiator fins are clear. Using an air hose and blow gun, blow through all of your radiator in the opposite direction that your fan is trying to push air through.

 

[Den N Ms]

SlowCredit , You didn't say,But what about the fan belt is it the right 5/8"width.Generator/alternator pulley 5/8"width and the belt tight.A lot of them are run loose,fan slipping and causing to over heat.Grab the fan blade and see if it will turn the engine over with out slipping.Check it out and be sure.
A lot of N Fords have a narrow pulley automotive alternator just slapped on and use a narrow 1/2" or 3/8" fan belt that will just slip on the fan/water pump pulley causing over heating.

This post was edited by Den N Ms on 05/10/2022 at 11:27 am.

 

[Bruce (VA)]

No, I read it.

Just gave him the 100% coverage of every possibility.

I'm looking forward to seeing the resolution of this; cylinders leaking into the water jacket would be at the bottom of my probability list. A clogged water
jacket of radiator seems most likely. But checking everything is always a good idea.
75 Tips

 

[SlowCredit]

First off - thanks again for any/all replies.

Long time consumer of 75 tips and this forum..

Den n MS - may be onto something - it's definitly an old 12v car alt. Got a new fan belt when I put on the water pump and it wouldnt fit the narrower pulley on the alt. Old belt is tight to 1/2 deflection, but could be slipping - fan seems to be spinning along. Will pull the alt in the am and see if i can fit a differnt pulley.

My best guess is still combustion gasses mixing with coolant. How to test if head, cylinder sleeves, block, ????.

Thanks!

 

[SlowCredit]

First off - thanks again for any/all replies.

Long time consumer of 75 tips and this forum..

Den n MS - may be onto something - it's definitly an old 12v car alt. Got a new fan belt when I put on the water pump and it wouldnt fit the narrower pulley on the alt. Old belt is tight to 1/2 deflection, but could be slipping - fan seems to be spinning along. Will pull the alt in the am and see if i can fit a differnt pulley.

My best guess is still combustion gasses mixing with coolant. How to test if head, cylinder sleeves, block, ????.

Thanks!

 

[old]

If you can turn the engine over by grabbing the fan then the belt is tight enough. As for testing rent a cylinder compression unit. It will put pressure to a cylinder and then you can see if you have bobbles in the coolant

 

[Eman85]

https://www.harborfreight.com/combustion-leak-detector-64814.html
This will test for combustion gasses in the coolant. Should be available at NAPA and most any parts store also.