Do I have a leaky head gasket?

[jonrick]

Hi Everyone,

I recently acquired a Cub Cadet 1450. It doesn't seem to smoke at all and apart from being a bit cold natured it seems to run pretty well. However, today I discovered that there is a small amount oil on the cooling fins after running it for a bit. Here are some pictures:

Thanks for reading and any insight you might have!

 

[mgonitzke]

Either that or a crank seal on the flywheel end. If you don't know the maintenance history, may as well just do both.

 

[jonrick]

Either that or a crank seal on the flywheel end. If you don't know the maintenance history, may as well just do both.

It was sort of a gamble purchase. The original owner bought it for parts but found it was way too nice to pull apart. He has no idea what was done to it before. I went through with the purchase because it seemed to run pretty well.

 

[HKCooper44]

Check-tighten all the head bolts first. I think they torque to 26/30 ft. lbs. That's an odd place to have an oil stain on cylinder fins, and seems to be about 3 fins down from the cylinder head parting line. Try positioning the piston at bottom dead center, then installing an adapter in the spark plug hole, then pump shop air into the cylinder. Squirt the cylinder fins with soap water or Windex and look for bubbles. If you see bubbles between the fins where the stain is, you might have a cracked engine block casting. Never saw this on a Kohler before, but I did find this once on several cylinder barrels of a Continental TSIO-520 aircraft engine!

 

[jonrick]

Check-tighten all the head bolts first. I think they torque to 26/30 ft. lbs. That's an odd place to have an oil stain on cylinder fins, and seems to be about 3 fins down from the cylinder head parting line. Try positioning the piston at bottom dead center, then installing an adapter in the spark plug hole, then pump shop air into the cylinder. Squirt the cylinder fins with soap water or Windex and look for bubbles. If you see bubbles between the fins where the stain is, you might have a cracked engine block casting. Never saw this on a Kohler before, but I did find this once on several cylinder barrels of a Continental TSIO-520 aircraft engine!

I was worried someone might say it could be a crack. I'll try re-torquing all the bolts. Unfortunately I don't have access to an air compressor where the cub is located. Do you think just squirting some soapy water in that area and turning the engine over a few times would reveal a possible crack? Also, are there any other signs I can look for that would indicate a crack?

Thank you for the insight!

 

[jonrick]

I'm hoping I'll get a clearer idea of where it might be coming from once I pull the engine cover/shield off.

 

[HKCooper44]

I was worried someone might say it could be a crack. I'll try re-torquing all the bolts. Unfortunately I don't have access to an air compressor where the cub is located. Do you thinking just squirting some soapy water in that area and turning the engine over a few times would reveal a possible crack? Also, are there any other signs I can look for that would indicate a crack?

Thank you for the insight!

 

[HKCooper44]

Unless your cylinder block has a BIG crack, it'll be next to impossible to visually check it from the outside, as the cylinder casting is very rough. Also, if the crack was large enough to see, the engine wouldn't run well, as you say it does. You might soak the area with the engine cold using soapy water then run the engine to see if bubbles appear. You'll have to be quick, as the soap solution will quickly evaporate as the cylinder heats up. If results are inconclusive, try cleaning the oil off the visible area with carb cleaner, then run the engine for some time to see if it returns.
See if a friend has a portable air tank you can borrow and try the pressure test, as I described prior.

 

[kharvey]

Why not just pull the head and inspect things. Install a new head gasket and let'er rip.

 

[jonrick]

Why not just pull the head and inspect things. Install a new head gasket and let'er rip.

Probably a good place to start. I'll order one this evening.

 

[-CӞ]

Not having witnessed the machine’s maintenance before acquiring it, I would start by cleaning off the errant oil.
If it doesn’t reappear after running the engine a while, it could be that it was merely a sloppy pour during a past oil change.
That said, torque-spec-ing the head bolts sure can’t hurt either!

 

[dsarow]

Head gasket and torque specifications are always a good maintenance item to keep up on .Lets hope your problem isn't a costly one

 

[jonrick]

I have an update, I'm fairy sure that it's the head at this point. I was working in the evening and happened to check under the hood with a head lamp on. When I rev'd the engine I saw a puff of smoke/vapor come out from what appears to be the seam. I wasn't able to see it in the day time. I see some re-manned heads on ebay and am thinking of going for one of those.
One question I have is; would a leaky gasket cause the engine to stumble a little when reving?
Thanks for everyone's input!

 

[HKCooper44]

Hold on! New heads are expensive, not to mention hard to find! Try this: pull the plug wire off and have someone crank the engine while you look and listen right at the head. Do you hear a "pfft, pfft"? Try to tighten the head bolts, especially the ones forward on the head. A bit loose? There you go! Remove the head. Keep track of what bolt came from what hole. Dust the mating surface with a bit of Krylon, then run the head back and forth on some medium sandpaper on a flat surface (like a kitchen counter when the wife's not around). This may take some time and elbow grease! Keep at it until all the paint is gone. Now, blow out all the bolt holes in the block with compressed air. Run a tap in the holes, if you have one. Put the head with a new gasket on the block. Wire brush the bolt threads and install each bolt dry with a plain washer (like an AN 960) and an internal star washer under the bolt heads (like an AN 936A). Torque the bolts in a star pattern to about 28 - 30 ft. lbs. This should fix the issue!

 

[mgonitzke]

Don't buy a new head. There is likely nothing wrong with the one you have that can't be fixed.

No sense in trying to tighten the head bolts without doing anything else. The gasket is already blown, so retorquing it is not going to help. No sense in keeping track of which bolts came from which holes other than where the studs for the lift point came from, and any different length ones. It will make no difference as long as the correct length/style fastener ends up back where it was. Also no need to paint the head before wet sanding it flat...it will be obvious when it is time to stop. Wet sand with 220 grit sandpaper on a sheet of glass until the sandpaper has touched the entire gasket mating surface.

Get a Kohler gasket, not aftermarket, oil the bolts and install them (NOT dry...this is per the service manual), torque to 25-30 ft-lbs in the pattern specified in the service manual (The service manual is a free download from Kohler's website). Use the original washers. If the are damaged or missing, the thick Grade 8 washers hardware stores sell are closer to the original ones than what HKCooper44 is suggesting above. Do not add lock washers of any kind.

 

[HKCooper44]

The Kohler service manual shows ways, which are not the only ways, to effect engine services.

 

[mgonitzke]

The Kohler service manual shows ways, which are not the only ways, to effect engine services.

It's generally a good idea to follow the manual when working on something...particularly in this instance here, the bolt torque spec is for oiled threads. Installing them dry will result in them all being under-torqued.

 

[dsarow]

Hoping that the advice on flattening the head and new gasket works for you.This is my thought,I would use a thread restorer and not a tap as they cut to aggressively. A thread restorer just reforms and moves the thread without removing metal.I use my kit on my old girl often,

 

[rfunk]

I'm agreeing with HKCooper. A head rarely cracks near the gasket. I had a cracked head - blowing gas out a very visible crack an inch away from the spark plug. I got lucky, my neighbour GAVE me a parts engine to steal the head from. I also sanded the replacement head before installing it, and, WOW, did the new head ever make a difference in starting. Any leak, gasket or crack, will steal vacuum, so you get less air-fuel mix in, and more plain air, so way too lean, even with full choke.

 

[jonrick]

It's generally a good idea to follow the manual when working on something...particularly in this instance here, the bolt torque spec is for oiled threads. Installing them dry will result in them all being under-torqued.

Please excuse my ignorance if this is a stupid question: Would some regular engine oil suffice or would something like WD-40 be better?