Small bubbles around head bolt.

Fri Jan 25, 2013 9:48 pm

Doing some tin work on the Cub and have the hood/tank off. Have a pony tank on it and went to try and start it today. Was not successful until this eve as its been super cold here in Pa. Like Single digits. As I was trying to get it to start, I noticed tiny water bubbles coming from around the bottom of a head bolt. The bolt is the one between the number 1 and number 2 cylinder, the one in the center of the head. Do I have a problem here? Do I pull this bolt out and put sealant on the threads and torque back down? Thanks

Re: Small bubbles around head bolt.

Fri Jan 25, 2013 10:08 pm

Evidently you did not get it started so the compression is the source of the bubbles. I can't see any safe way around taking the head off and replacing the head gasket. You don't want to take the chance that water is leaking into a cylinder and will stay there a while and do much damage.

Re: Small bubbles around head bolt.

Fri Jan 25, 2013 10:12 pm

Slightly different opinion.

Did you coat each head bolt with some sort of sealant to keep coolant from seeping up the bolt threads? If not, I would drain the cooling system. Remove one bolt at a time, add sealant to threads, and retorque.

Re: Small bubbles around head bolt.

Fri Jan 25, 2013 10:13 pm

If you do replace the head gasket, apply some Indian Head brand gasket sealer to the head bolt threads during reassembly as a back-up precaution. If you find any of the threads on the head bolts to be deteriorated from rust when you remove them---be sure to replace them.

Re: Small bubbles around head bolt.

Fri Jan 25, 2013 11:09 pm

For a short term fix, I've drained the cooling system, pulled the bolt, cleaned the threads, applied thread sealer, installed the bolt, torqued it down, and re-torqued after one heat cycle. Worked fine until I had time to pull the head and resurfaced it prior to re-installing it. Resurfacing was probably overkill but I wanted to be sure that I hadn't messed something up with my quick fix.

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 6:11 am

I did get the engine started later in the day when it got near 15 degrees and it ran fine and smooth as always. This might have been going on for a long time but never noticed with the hood on. Will pull the bolt and apply Indian head. Sure hope bolt comes out and doesn't break or the head will come off. Am I better off trying the bolt removal with a hot or cold engine or doesn't it matter? Do know to work it back and forth like a tap as I break it free.

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 6:56 am

Dan Stuckey wrote;
Am I better off trying the bolt removal with a hot or cold engine or doesn't it matter?

Always try to remove all engine head bolts with the engine at shop temperature. If the head bolt doesn’t come out easy try moving it back and forth until you get the head of the bolt off the engine head than try applying some rust break down the bolt hole.

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 7:09 am

I have had good luck with an impact wrench on the head bolts, seems less likely to break that way.

When I was going over the 77 I found a small amount of coolant on the top of the head, tiny crack in the head. The crack seems to seal itself when the engine got up to temp. I went to use the head off the spare Cub and it had a crack in the exact same place. When I put the new one on I used Hylomar for a thread sealant, sort of a non-hardening RTV. haven't run it long enough to say how well it works.

Image

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 8:24 am

Dan Stuckey wrote:Will pull the bolt and apply Indian head. Sure hope bolt comes out and doesn't break or the head will come off


Dan, if the bolt is stubborn backing out, tap the head of the bolt with a hammer a few times, then use your impact wrench as you mentioned, but turn down the torque to a lower setting first, then advance it up higher.

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 8:29 am

I've got one, and I suspect quite a few others as well, have the same hairline crack as Buzzard Wing. The coolant would pool around the head bolt. The crack is now residing under a liberal application of JBWeld and hasn't been heard from since. I just left the pretty grey looking like a bandaid. If it ever gets painted then the head will be properly repaired or replaced.
It sounds more like yours is the bolt leaking but the crack is worth looking for just in case.

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 9:07 am

That is where there will be a crack if it freezes , was the week spot
Boss

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 9:12 am

Between 2 and 3 cyl.

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 10:52 am

Dan, remeber, that when you pull that head bolt you will get an antifreeze fountain if you do not drain enough antifreeze before you remove it. Since it was bubbling before the engine started, yo may have a coolant leak that the thread compound will help, but you also have a compression leak the the thread sealer will not help. It will stop the fluid from coming up, but if you put a little water or soapy bubbles around the bolt you will still see the leak. The compression leak will be a head gasket most likely.

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 2:18 pm

If you do the temporary fix, keep the radiator filler cap loose so the cooling system does not pressurize. This will also help to reduce the amount of leakage through any head cracks.

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 3:24 pm

Most of the time the crack is long ways, B Wing, That may have been a crack caused by something under the head when it was tightened down