AC model C - coolant in oil

Hi all,

I noticed a little antifreeze in the oil when
doing an oil change last weekend; Dad told me I
had better get it fixed before mowing any more
(it's his tractor). I searched around this site
for a while and read up on some common causes
(frost plugs in the head and sleeve seals) I
removed the rocker arm cover today and immediately
noticed all three frost plugs had antifreeze
sitting in them. To prove to myself that this was
indeed the source of the leak I went ahead and
shop-vacked up the antifreeze/oil mixture out of
the frost plug "cups" and then pressurized the
radiator to about 4 psi. Antifreeze leaked out of
the radiator in several spots but none seemed to
seep through the frost plugs. Next I pressurized
the system to about 7 psi ; still no leaks from
any of the frost plugs, just from the leaky
radiator which caused the pressure to drop off
real fast. The frost plugs appear to be in good
shape (not too rusty) sooo is my coolant leak most
likely from elsewhere and not the frost plugs (ie
the sleeve seals) or is the leak so small through
the frost plugs that I can't detect it. I guess
I'd like to know if I should bother replacing the
frost plugs or if I need to keep searching for a
more severe leak. It's probably worth mentioning
that the amount of antifreeze in the drained oil
was not all that significant - but rather just
enough to notice that it was there (some dark
green liquid mixed in). Thanks for any help you
guys might be able to offer!
 
Could be that when the motor warms up and the metal starts contracting and expanding it causes the plugs to leak where pressure alone won't do it? Just a thought.
 
If you saw anti-freeze in the freeze plugs, they need to be replaced. Anti-freeze couldn"t get there from any other source. Like Lonnie said, It probably leaks when it gets hot. LOL Bob
 
You will have antifreeze anywhere that oil goes so don't count on freeze plugs. However they are only $5.50 each. Keep searching, other possibilities are head gasket (not too expensive)or "O" rings on cylinder liners which is a major job. To check cylinder liners take off oil pan and look for antifreeze leaking around liners with pressure. I just did this on a C and it was readily apparent mine was a freeze plug (had a hole in it).
 
I'd pull the freeze plugs, as others have said, no other way for AF to get there, and $16.50 won't break you. Keep your eye on the oil pan, though, by loosening the drain plug, if there is AF leaking internally, it will migrate through the plug threads, with the plug still in loose. Oil needs a bigger gap, to leak through. Do the drain plug test on a cold motor.
 
change out the freeze plugs, then go to Auto Zone and get a bottle or BARS copper head gasket sealer. Pour about half (5-6 oz) of the stuff in the radiator with the antifreeze and go for a 20 minute ride. YOu will be suprised at the results.
 
If you diden't have the engine running when you pressured the system you could very well have an air pocket in the top of the head water jacket. You would need to put oil in the core plug pocket and look for bubbles to be sure.
If the engine is running with antifreeze leaking on the bottom side the oil would become milky and you would not see a color in the core plug pocket.
 
Thanks for all the tips guys - really appreciate it! I think I'll go ahead and drop the oil pan this afternoon and re-pressurize the system; fingers crossed this isn't the source of the leak as I have very limited engine experience. Also sounds like it wouldn't do any harm to just go ahead and replace those frost plugs since they're cheap enough - do you seal them with permatex then? I'll let you know what I find as I'm sure I'll have more questions as I go. Thanks again
 
Hi Noah I,m painting a C and fixing oil leaks. Cleaned out the block of all the rust and wanted to check liners for water leaks. Filled with water and pressurized system with pan off found water leaking from the front cover thats bolts between waterpunp. Will have to front cover You may want to check that out if a gasket is bad
good luck

Rod in MN
 
Dick L-

I did not have the engine running when pressure testing. Per your suggestion, this morning I filled the three core plug pockets with oil and re-pressurized to 7 psi - still no air bubbles or coolant leak. I then proceeded to drain all the new oil I had just filled it with and then drop the oil pan. I would estimate at least two cups of water/antifreeze poured out the drain plug before uncontaminated oil started to flow. Next, I again pressurized the radiator and looked up into the engine to check for leaks around the cylinder sleeves - still nothing. Now I am thoroughly confused! - how can it be that after changing the oil, driving it back into the shed, and then doing various pressure tests that I could accumulate two cups of water in the oil pan and now when I pressurize the system with no oil pan attached that I see no coolant flowing down into the open cavity where the oil pan would be? Please forgive my ignorance as I'm a novice at engine work, but I thought that regardless of the leaks location I would see antifreeze drain back to the oil pan. Any advice? Do I need to pull the head next and inspect the head gasket? Thanks again for any advice!
 
It could well be a heat related type of leak and those can be hard to find at times. A head gasket or sleeve o-ring either one can leak when warm/hot but not leak when cool
 
Noah, if time and money are tight, im serious about putting a cup of Bars copper head gasket sealer in the motor. Whave have you got to loose? $10. and you will be happy for now. IF and when you want to overhaul the motor, you do need to pull the liners, replace the old o-rings and reseal... in addition to the new head gasket.
 
Steve -
I appreciate the suggestion; seems time is tighter than money but neither are "loose" (wife, baby, & broken down tractors to support) so I suppose no, I don"t have much to lose. But...I don"t have any dire need for the tractor as of right now so I"m not entirely afraid of a tear down; I already stripped the electrical components off so I could power wash 30 years of accumulated gunk off and the brakes are broken as well so I anticipate an over-winter project as is. I guess I am thinking I will use the bars leak as a radiator fix if possible but I would like to pursue a more permanent fix for the oil contamination problem. Seems that if I accumulated 2 cups or so of coolant in the oil pan in a few minutes of run time and pressure testing combined that the leak may be too severe for a bars leak type fix? Again, I"m new to this tractor fixing business...Thanks for the advice!
Regards
 
Today I replaced the third freeze plug, wasn't leaking but after two leaking ones , I wanted to be safe. It would have gone sometime as it was very thin.
 
Sounds like a pretty big leak. I would drop the oil pan, and do the leak down test again. You might just have a cracked cylinder sleeve o ring. Might be able, to just replace the leaky one, if you can ID it. Whatever you do, don't let the AF get into the oiling system, it eats up the bearings.
 
We have a machine shop and recondition many heads and blocks. I would no recommend using any type stop leak in the cooling system. Working on the interior of these engines is about like repairing a tire that has slime put in it.
 
old-
I'm starting to think this may be the case (leaks when hot but not cold). I pulled the head tonight and inspected the gasket. I didn't see any obvious blow-outs or staining (of course this is the first head gasket I've ever seen - what other clues on the gasket/mating surfaces should I be looking for?). I checked the head and block mating surfaces with a straight edge and they seemed as true/flat as a framing square can indicate...now on to the possibly interesting part...I took another look up into the engine tonight from where the oil pan would be and noticed some black crud hanging from the outside surface of a couple of the cylinder sleeves where they interface with the block. I reached up in and grabbed a chunk with a needle nose - it appears to be the dried up remnant of an oring?! could this be the case? Could it be that they are so rotten and hardened that they've made their way down the sleeve and exposed themselves? I plan on pulling this sleeve tomorrow night if time allows to further inspect. Please let me know your thoughts - Thanks again all - your advice thus far has been a great help
 
Could be part of an o-ring but not real likely because if it was the sleeve would most likely leak all the time. As for the head gasket it seals the top of the sleeves and can be easy to leak there if the sleeves do in stick up just a very little bit. The sleeves should sit up just enough that if you run your finger nail over them you should catch you nail on the sleeves. If not then that could be your problem BTDT and had once where the block was planned with the sleeves in and that in turn cause the sleeves to leak
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top