Head gasket

[kenv52]

I have a Husquvarna tractor. 18.5hp. Can anyone tell me why I have gone thru 4 head gaskets? This one being the 4th. Blows out right across from the plug. There is no way I screwed up 3 headgaskets. Getting a little tired of this crap. Are these engines junk? I can change a hot cylinder in a 2500hp EMD but can't keep this running. Should sell everything and buy a diesel....

I have a zero turn with a Briggs intek 18.5. I also have a friend that worked for a country clipper distributor for years. I’ve put two on mine so far. He said that engine is known for blowing head gaskets and that a lot of dealers would refuse shipment if it had that engine. It runs fine other than that. He even told me where it blows at and sure enough he was right. It did it two times. It then leaks compression into the block and blows oil out the vent/breather thing on the side of the motor. It’s important to re torque the head bolts after a mow or two after installation. I’ve been thinking about just buying another head gasket kit and having it on hand

 

[Gord Baker]

Certain belt sanders have wide adhesive backed grit. Attach a long length to a FLAT piece of Steel and sand ead, rotating it often. Check with light and straight edge.
Ditto with flat piece of steel to Block. Are you using OEM gaskets. Torque and sequence are very important.
Perhaps try with copper anti-seize applied sparingly to both sides of gasket. Good luck. Check Crank for partially sheared key. Incorrect timing could cause excessive temps and pressure perhaps.

 

[Moparjoe499]

I have a Husquvarna tractor. 18.5hp. Can anyone tell me why I have gone thru 4 head gaskets? This one being the 4th. Blows out right across from the plug. There is no way I screwed up 3 headgaskets. Getting a little tired of this crap. Are these engines junk? I can change a hot cylinder in a 2500hp EMD but can't keep this running. Should sell everything and buy a diesel....

Get a concrete block, lay the block down and take the head and rub it on the concrete block a couple times. Look at it and you will see where the low spot is. Keep rubbing it until the low spot disappears. I have done this before and it works.

 

[Piros1]

Sounds as you are skilled at engine repair but I will throw something out I did not see mentioned. Did you clean both head and block surfaces and check with a good straight edge to be sure they are flat and not damaged or pitted?

 

[Bushbunnie]

sounds like a flaw in the head

 

[Roy405]

I have a Husquvarna tractor. 18.5hp. Can anyone tell me why I have gone thru 4 head gaskets? This one being the 4th. Blows out right across from the plug. There is no way I screwed up 3 headgaskets. Getting a little tired of this crap. Are these engines junk? I can change a hot cylinder in a 2500hp EMD but can't keep this running. Should sell everything and buy a diesel....

I'd have to think something is not flat.

 

[Curtisun]

This is only true for CAST IRON engine blocks where the head bolts are done up to 100 ftlbs of torque or there abouts .
If you think 20 ftlbs into alloy is going to cause any structural change to a bolt, even a grade 3 bolt then you must have been asleep during your science classes at high school or gone to a school that teaches creationism and languages with no science at all .
When torquing down into alloy you damage the hole not the steel bolt which is why quality alloy engines use inserts , to protect the block.

On bolts
Higher tensile bolts have deeper cut threads so there is more surface area of metal to metal contact to create more friction between the bolt & the hole which is why the bolt stays in there and why using a grade 9 bolt seems to hold better, nothing to do with the tensile strength of the steel.

Please try not to conflate automative technology with mower technology where there is almost none .

Then I ask why it specifically says to replace head bolts in manuals for aluminum block and heads.
I had a 4-wheeler with aluminum block, 650 cc that keep blowing head gaskets after a few hours of running. I made sure there was no cracks or warpage. Come to find out after I finally found a manual on it and after 5 head gasket replacements it stated, "Head bolts must be replaced when head is removed for any reason". It did not give a reason. I purchase all new head bolts and it has been running for about a year now with no problems.

 

[Joed756]

If you have done all of this already, try using two head gaskets. Often that will make up for any head deformities.

 

[lofty66]

Almost certainly a warped head, but some of the methods being suggested here to flatten it are a good way to ruin a perfectly good head. Do not use sand paper or concrete both are far to coarse and inaccurate. The best way is to use fine valve grinding paste on a piece of glass, preferably 1/4" or thicker as that's flatter. Do not use a scrap double glazed panel as they're often slightly concave. oil the glass, then smear on some fine valve grinding paste. Place the head on it and move in a figure of eight motion, every dozen or so figures of eight stop, turn the head through 90 degrees and continue. Every so often lift up the head and check the lapped surface, low spots will be obvious. Continue, adding more grinding paste as necessary, until the whole surface is an even mat colour. Wash off, then refit using a new head gasket and torque down gradually, ie bring the bolts up together, do not torque down one fully then the next and so on. If the order is not known tightening diagonally is a good rule of thumb.
One other thing to check is to make sure the bolts (or one possibly) aren't bottoming out too early. Without the head try fitting them, and make sure when fully inserted the gaps between the block and the head of the bolt are all less than the thickness of the head. If they are bottoming out, even when torqued down they won't be squeezing the gasket correctly.

 

[G5200]

Had this problem with a 21 HP B&S about 15 years ago. The key that positions the flywheel (and magneto) relative to the crank (times the spark) had partially sheared, causing the spark plug to fire too early. Preignition - overpressurized the cylinder and kept blowing out head gaskets. Check your TDC vs when the cams move the valves.