Mahindra 5555 engine over-revved & DIED!!!

Tx Jim · Oct 4, 2020

My neighbor told me yesterday the engine on his 5555 with 2000 hrs that he purchased new had the engine uncontrollably over-rev & die then wouldn't restart. Mahindra dealer stated tractor will require a NEW engine.

RickB · Oct 4, 2020

Surely that is not the first runaway you ever heard of?
Maybe it needs a new engine, maybe the dealer does not want to risk repairing an engine that may only need fuel system repairs. Maybe the dealer knows his techs are not capable of an engine rebuild that he wants to stand behind.

Tx Jim · Oct 4, 2020

Rick
No it's not the 1st diesel engine I've heard of that's exceeded recommended rpm's BUT it's seems odd to me for this 2000 hr engine to overspeed with an untouched fuel system. I suppose this engine has an incorporated governor that possibly could have failed. I'm aware IP governor drive rings in rotary type IP's can deteriate but it took longer than 2000 hrs of use.

the old grind · Oct 4, 2020

Turbo bearings can fail/leak and add lube oil to the intake stream. When it happens in a car engine it can run but smoke like a fogger until dealt with. (seen it with 2x GM 3800 V-6 turbo Park Avenues with high mileage and few if any cool-downs AKA spin-downs at idle by inexperienced 2nd owners.)

IMO any turbos need a more diligent, longer cool-down before shutoff than NA engines to reduce cooking bearing seals. No to suggest that as the cause or criticize the maker or operator, just a possibility, and parts don't let us choose when they'll die short of expected lifespan.

Hate to hear of this happening. What's done is done. The neighbor is lucky to have Jim close by to help him analyze, and we're lucky to have him here to keep us up on where this goes.

Tinhack · Oct 4, 2020

I'm betting it's an IP problem also. A pump is a lot cheaper than an engine.

The fact it's cranking is a good sign. More diagnostics are required.

ruffdog · Oct 4, 2020

Tx Jim said:
Rick
No it's not the 1st diesel engine I've heard of that's exceeded recommended rpm's BUT it's seems odd to me for this 2000 hr engine to overspeed with an untouched fuel system. I suppose this engine has an incorporated governor that possibly could have failed. I'm aware IP governor drive rings in rotary type IP's can deteriate but it took longer than 2000 hrs of use.

A runaway is much more than just "exceeding recommended rpm's". Diesels do not have a throttle plate to govern engine speed. Instead, they vary the amount of fuel from the pump that is governed to get the desired rpm. A unintended fuel source like crankcase oil past a blown seal will allow the engine to runaway. When this happens, the injection pump and governor have lost the ability to control rpm.