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Causes Of Loose Cylinder Head Bolts


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#1 kiddpitt OFFLINE  

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Posted October 22, 2013 - 06:57 AM

Hello all, I need some help from people more knowledgeable than myself about small engines.

 

Over the weekend I was plowing some dirt with my '72 LGT 100 and noticed I was losing oil; about 4 oz a day.  I usually lose that much between oil changes, not between uses, but the tractor was running fine and I noticed no loss of power or performance.

 

I looked everything over and noticed oil on the top 2 cooling fins on the front of the engine.  I also noticed the crankcase breather was covered in muck, which I cleaned.

 

Thinking I have head gasket issues, I began disassembly.  Before removing the head, I noted that only 2 or 3 of the cylinder head bolts were still tight enough.  Most need another 5-7 ft lbs of torque.  I didn't have time to pull the head off. 

 

I also pulled the spark plug and it was dry, sooty black. I had just checked the plug a couple weeks ago and it was grey, so something happened recently.

 

What could have caused the bolts to loosen?  Time/age?  Carbon buildup & warpage?

 

I "think" the head bolts have been loose for some time and that the clogged breather pushed the oil through this convenient place.  I also think this looseness plus the pressure from the clogged breather caused low compression, which caused the carbon in the last couple weeks.  I always run Chevron Techron in my gas and check the spark plug during the season.  Carbon buildup has never been a concern. 

 

I have no reason to suspect that I overheated.  No pinging, knocking, smoking, etc.  I'm tempted to just tighten the cylinder head in sequence and see if the oil leak goes away, but I don't know if that's prudent.  I take good care of this thing and don't want to shotgun a repair; if the head should come off, it will come off.


Edited by kiddpitt, October 22, 2013 - 07:23 AM.

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#2 MH81 ONLINE  

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Posted October 22, 2013 - 07:07 AM

When was the head last off? If its been a long time and those bolts haven't been out... Hmmm. IDK why they would... Not an aluminum jug, is it?

As for what to do now, I would probably take the head off and clean up the oil and decarbon. The stuff in there. Check valves and all that. You might get it to stop leaking, but there will always be oil on there to help the next leak occur. And Murphy says it'll be at an inconvenient time.
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#3 Gtractor OFFLINE  

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Posted October 22, 2013 - 07:13 AM

I agree, take the head off and clean everything inside.  Not sure if you have washers under the head of the bolts but make sure the washers on the head bolts have a "cup" to them.  The tension of the cup being compressed is what holds the bolts tight - working like a lock washer. 


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#4 kiddpitt OFFLINE  

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Posted October 22, 2013 - 07:29 AM

When was the head last off? If its been a long time and those bolts haven't been out... Hmmm. IDK why they would... Not an aluminum jug, is it?

Not sure what you mean by aluminum jug, but it's an aluminum head on a cast iron block. 

 

I have never had the head off.  The previous owner said it was used for a few years in the 70's, but was pretty much unworked between then and me.  I bought it 3 years ago and it has tilled, mowed, plowed and pulled with no trouble. 

 

 


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#5 skyrydr2 OFFLINE  

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Posted October 22, 2013 - 07:34 AM

Remove the head , inspect and clean, check valves for leakage too , You can even check the guides at this point. Be sure you make sure the head is perfectly flat and true before re-assembly, if not glue a new sheet of 100-150 grit sandpaper to a flat surface and sand the gaskeet surface of the head flat. Re-assemble and run it for a while to get it hot. Let it cool down and re-torque the head bolts one more time.


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#6 boyscout862 ONLINE  

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Posted October 22, 2013 - 07:43 AM

I think the big culprit is the breather. It probably pushed oil into the carb. Do the head work and use a new head gasket. Before you reassemble, take the breather off and clean and check it. At this point, lapping the valves and adjusting the valve gap would make sense. Our Manuals Section has excellant manuals that you can download for the engine and tractor. Three free per day. Good Luck, Rick

Take some pics before during and after the work. We like to see pics and they will help your memory for reassembly.

Edited by boyscout862, October 22, 2013 - 08:29 AM.

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#7 kiddpitt OFFLINE  

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Posted October 22, 2013 - 08:27 AM

Thank you all.  I have all the manuals for the tractor, including the service manual that I printed. 

I've done the head gasket & relapped the valves on the 145 I have, so there's no reason for me not to fix it right the first time.

 

Hopefully, seeing what's under the head helps me figure out why this happened.  I can fix these problems, but I really want to find the cause so this doesn't happen again.

 

Is 100-150 grit sandpaper really fine enough for flattening the head, or should I start there and finish with a finer grit?

What's the best way to clean the carbon from the piston and valves?  I know the manual calls for a putty knife, but that seems like a good way to get carbon flakes/dust between the piston and cylinder.


Edited by kiddpitt, October 22, 2013 - 08:36 AM.

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#8 LilysDad ONLINE  

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Posted October 22, 2013 - 08:42 AM

A putty knife is a good way to scratch the piston. Permatex Gasket Remover will desolve it in minutes. Some folks use those scratch pad thingees on a diegrinder.


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#9 kiddpitt OFFLINE  

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Posted October 22, 2013 - 08:53 AM

A putty knife is a good way to scratch the piston. Permatex Gasket Remover will desolve it in minutes. Some folks use those scratch pad thingees on a diegrinder.

 

 

I actually read about using the Permatex Gasket Remover during my research.  Do you relube the cylinder walls after using it to decarbonize?


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#10 skyrydr2 OFFLINE  

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Posted October 22, 2013 - 10:00 AM

 Too fine a paper will only clog up and give you a false truing . You can also see if the piston/ rings are bad , but only if they are really bad. Check for cylinder wall wear too . I'm with the others on the breather , it needs to function correctly.


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#11 JDBrian OFFLINE  

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Posted October 22, 2013 - 10:53 AM

I had a K321 with a bad HG and spitting oil out the breather. After removing all the carbon and replacing the HG the breather problem went away. It could be that the head bolts were never evenly tightened. a difference of 5-7 lbs is not that much but could have lead to premature gasket failure. The K series service manual gives a detailed procedure for doing the HG including the order to tighten the bolts.


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#12 kiddpitt OFFLINE  

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Posted October 22, 2013 - 11:18 AM

IIt could be that the head bolts were never evenly tightened. a difference of 5-7 lbs is not that much but could have lead to premature gasket failure.

 

I agree, 5-7 lbs isn't much, but it's a large percentage of the 25-30 ft/lbs that are called for.  Some of my bolts were still tightening with the torque wrench set at 20 ft/lbs. 

 

I also agree, I need to get the head off and see what's actually happened in there.  I think the fear of piston or cylinder damage is why I hoped to avoid that step, but if there's any damage like that, I need to know.  If there's not, I can button it back up knowing everything is good.

 

I haven't posted on this forum in about 2 years, it's nice to see how willing to help you all have been.


Edited by kiddpitt, October 22, 2013 - 11:25 AM.

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#13 LilysDad ONLINE  

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Posted October 22, 2013 - 01:03 PM

 

 

I haven't posted on this forum in about 2 years, it's nice to see how willing to help you all have been.

Well . . .   I wasn't going to mention it. But, since you brought it up . . .

 

 

 

 

 

 

We still love you. :big_hug:


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#14 EricFromPa OFFLINE  

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Posted October 22, 2013 - 07:36 PM

Some head gaskets will deteriorate over time causing the head bolts to become rather loose,heating up and cooling down over the years will cause the studs to stretch just like in a car with High mileage engine.

 

It's always good to re-torque your head bolts every couple years on all older machinery.


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#15 kiddpitt OFFLINE  

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Posted October 23, 2013 - 05:46 AM

I took the head off last night & boy!  I'm glad I did!

 

I didn't check the head yet to see if it's warped, but there's no signs it overheated & the gasket isn't blown.  There is quite a bit of chunky, crusty carbon.  I'm glad I didn't just tighten everything back up & try to Seafoam this junk out.

 

This evening, I'll clean the crust off and check the cylinder for damage.  I got it to TDC before taking the head off & I want to clean everything before I check the cylinder wall.  Hopefully none of this crust got down there.

 

I took pictures and I'll take more tonight. 

 

Is anyone using a billet breather cover from Kirk Engines?  It's nice looking and looks like it may have prevented my breather from clogging up in the muck.     


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