Bent Push rods on Z445 Zero Turn Lawnmower

[retired duckhunter]

I have a JD Z445 Zero Turn 48in mower with a Briggs& Stratton 27 hp engine that bent two pushrods in one cylinder(pushrods in other cylinder OK)while under warranty at 271 hours.

The dealership told me this was caused by carbon buildup from the gasoline we are forced to use.

I could be wrong, but it's my opinion this could be a timing problem. Both pushrods shined with some discolor on one, the other had no discolor. Can't remember a pushrod bending due to carbon buildup. I've seem valve guides worn due to sludge from not changing the oil but no bending of the pushrods.

I use the same gasoline that is used in my other vehicles/equipment and the oil is changed per the maintenance schedule.

Just wondering if others have had this problem. I'm just attempting to get this engine in good shape before the warranty expires soon.

 

[ILENGINE]

I can't think of a single time that I can claim carbon for bent push rods. Most of the time it is due to overheading of the head causing the valve guides to move outward, preventing the valves from fully opening. On some engines one of the push rods is aluminum which could explain the color difference.

 

[mechanic mark]

https://www.briggsandstratton.com/us/en/shop/parts-and-accessories/fuel-additives

 

[retired duckhunter]

Thanks ILENGINE.

Yes, the pushrod with no discolor is aluminum.

Just got the mower back today after another week at the service dept. with a severe oil leak coming from the crank case gasket.

Seems this mower spends more time at the dealership than at home.

It has had problems with the hydraulics and parking brake.

I think I have a lemon.

 

[Fish]

What have they charged you for the engine so far?

 

[motoman]

Duckhunter, Sounds like you have the Intek which I have. IL Eng is right, pushed guides could do it , but my "first" pushed guide on one cyl very slowly ground down the cam to a circle, but did not cause a bent pushrod. Perhaps the explanation your dealer should have suggested with carbon is this, heard on other forums. Engine runs too hot by nature and at shutdown the "sudden" cold (compared with the 325F it was running at) causes oil to "coke" (form carbon deposits) the inside of the guide. When the next cam cycle occurs (lift phase) the pushrod is still momentarily "frozen" in a closed position and cannot move with the cam so the pushrod bends . Sometimes the pushrod will drop out and be found laying loose. Before replacing the head containing the pushed guide I reinstalled the pushed guide (this is a no-no) . The engine ran for a while and then did what IL Eng said, bent the pushrod. As a special treat the pushrod was launced down thru the oil return passage into the sump and chewed on by the timing gear , requiring a second teardown. (See pictures this forum)

The Intek has run well since watching the oil temp carefully. I suggest running the Intek at fast idle for at least five minutes after a hot hard day to reduce the oil temp. Better yet is an oil cooler. Still better is liquid cooling if you got the scratch.

The sump bolts will loosen by vibration . Most of mine fell out and I found them sitting on their heads. Then crankcase pressure will blow out parts of the gasketing . I have limped along by chasing any looseness and suffereing oil weeping to avoid yet another teardown.

My Intek is in a Craftsman dyt 4000. I have noticed the fancier terms and badge engineering B&S is using on the V motor now, and have repeatedly asked what the design improvements are with no answer. So it's still just an Intek.

 

[retired duckhunter]

More "good news" about my Z445.

Got it back from the repair on the crankcase oil leak, ran great for approx. 30 minutes then the clutch came loose and almost fell off.

Back to the dealer. Seems the bolt that holds the clutch on the crankshaft had fallen out. Found it in the field later.

Told the dealership I had had it with this mower. It was almost 4 years old and approx. 20 hrs. from end of warranty but they gave me almost what I paid for it as a trade in.

I now have a new Z445 with a Kawasaki engine. Hopefully it will stand up better than the Briggs and Stratton Intek.


Fish,

The mower was still under warranty so no charge for the "repairs". Just time and gasoline back and forth to the dealer(60 miles round trip), which wasn't fun to say the least.


Thanks to all for all the input. This is a great forum.