Engine died and leaking from...

[TurboDZL]

I posted this over on SC but I need answers/suggestions quick so here goes....


My 4.6 was on it's 8th tank when it shut down. I had already ran 3 tanks through it up and down the street today, I pulled up to a curb, blipped the throttle and get high centered, I blip it again and it dies.

Here's where it gets wierd. I go over to re-start and it and it has no compression, I notice fuel dripping from the exhaust and from under the truck. When I take a closer look to see where this other dripping is coming from I find it dripping from behind the flywheel. knowing something is not right I pack up and head back to the house for a better look. I get it home and give it another pull and now it has compression I pulled the plug out and the piston is moving (what a relief). I didn't try to re-start it because of the leak I saw behind the flywheel still had me spooked....What just happened and what should I do to troubleshoot?

BTW...temp outside was 39 deg / highest engine temp was 221 and still running rich with a nice size blue smoke trail at all RPM's.

 

[FastEddy]

Please excuse my ignorance but what is a 4.6?

 

[AC48]

He is talking about the HPI K4.6 engine, its a .28. Stock engine in the HPI Savage SS 4.6 kit.

I think your crank bearing might need replacing. The loss of compression sounds like your engine overheated to me. When the engines are very hot they have less compression usually.

 

[FastEddy]

He is talking about the HPI K4.6 engine, its a .28. Stock engine in the HPI Savage SS 4.6 kit.

Thanks,
I'm only half as ignorant as I was 5 minutes ago.

 

[TurboDZL]

I was real careful not to get the motor to hot. Like I said before, the hottest I seen it was 221, I was checking the temp every other trip up and down the road and everything seemed to be going well until I tried to hop the curb from a stand still. What would cause a crank bearing to go south...provided my engine temps were in check the whole time?

 

[FastEddy]

Mechanical parts do fail. If its spewing fuel from the front of the crank. its either a bad bearing or a cracked case. If it has compression now its most likely a bad bearing. Take it apart and look. Its not that big of a job.

 

[FastEddy]

Before I sat its not that big of a job, have you ever torn a mill apart?

 

[TurboDZL]

Nope, this is my first RC and only the second day I had it out. I've already pulled the motor out preparing for the inevitable (tearin-r-down). No visable cracks in the case so I guess, for now anyways, that rules that out.

I have one of those RC magazines that had an article on how to rebuild a motor so I guess I can use that as a guide... and with a little help from here of course.

 

[jon2]

Have you inspected the engine crank case?

 

[TurboDZL]

No visable cracks in the case so I guess, for now anyways, that rules that out.

Everything looks ok from the outside. I did notice however, there is a little (ever so slightly) in and out play on the crank shaft, no side to side movement though. I didn't notice and didn't check this when it was new so I don't know if that's normal or not.

The bearing was still slightly wet when I initially pulled the motor out and after wiping it dry the bearing appears to be in good order. Is the bearing shot regardless? I'd like nothing more than to just replace it but before I go tearing into the motor I want to hear what HPI suggests.