Snapped timing belt?

[Falcon_LS]

Vehicle in question is my '00 Montero with a 3.0L V6. I was driving home this evening, and had to merge with fast traffic on the highway. I floored the gas pedal and whilst the engine was at 5,000 rpm there was a loud bang, almost as though the muffler burst. Following this, the engine rpm dropped momentarily to 1,500 and then down to 0. I safely pulled to the side, and tried restarting the engine...it turns over but does not start? Any ideas as to what this could be?

For some reason, I'm thinking timing belt...but I religiously change it at the 80,000 km (50,000 mile) mark.

Thank you.

 

[JTK]

If it's the same 3.0L V6 as used in the US version of the Montero Sport, it's a valve crasher. Can you pull the oil fill cap and see valvetrain moving while someone cranks over the engine?

Joel

 

[Drew99GT]

When you turn it over, does it sound different then before, like there's hardly any compression in a some of the cylinders?

That does sound like a timing belt failure.

You could also pull the distributor cap and crank it, as most distributors are driven by the cam/cams. If it ain't turning, then you'll know.

 

[Falcon_LS]

Thank you for the response. I believe the 3.0L V6 in the US version is a 24-valve engine. Mine is a 12-valve, and the oil fill cap is connected to the valve cover with a hose. So unfortunately, there isn't much to see.

 

[Falcon_LS]

Originally Posted By: Drew99GT
When you turn it over, does it sound different then before, like there's hardly any compression in a some of the cylinders?

That does sound like a timing belt failure.

You could also pull the distributor cap and crank it, as most distributors are driven by the cam/cams. If it ain't turning, then you'll know.


It doesn't sound different at all, not faster or slower either. It just cranks as normal. I will remove the distributor car and see if it spins, thank you for mentioning that.

 

[Drew99GT]

Originally Posted By: Falcon_LS
Originally Posted By: Drew99GT
When you turn it over, does it sound different then before, like there's hardly any compression in a some of the cylinders?

That does sound like a timing belt failure.

You could also pull the distributor cap and crank it, as most distributors are driven by the cam/cams. If it ain't turning, then you'll know.


It doesn't sound different at all, not faster or slower either. It just cranks as normal. I will remove the distributor car and see if it spins, thank you for mentioning that.


Checking the rotor will only work if it's driven by the camshaft, which it is most times with an OHC engine design.

 

[BuickGN]

It's not the belt.

It would not have momentarily gone down to 1,500rpm before shutting off. It would turn over super fast with the loss of compression.

We had a chain failure in one of our cars and there was a subtle pop back through the intake and it was dead.

 

[Drew99GT]

Prehaps the belt slipped?

 

[Falcon_LS]

The rotor inside the distributor is spinning. I suppose that ticks off the timing belt. Anything else that would cause such a problem?

 

[mechtech2]

REALLY check the belt first. This is your basis. A compression check is in order.
It could have slipped timing and bent a valve, but still turn things.
There is more than one way to have a faulty timing belt system.

 

[duaneb9729]

Before tearing anything apart, i would check for spark and fuel, cover all the basic stuff first

you could take out one spark plug or use an old used one that you have laying around and plug it in to the spark plug wire or coil wire let the part with the threads touch a grounded surface such as the engine and have a buddy turn the key, then watch for spark

 

[labman]

+1

 

[Falcon_LS]

I'm actually beginning to think it's the fuel pump, but I will check everything to make sure before hand - especially with it costing $370.

 

[Falcon_LS]

As silly as this will sound, the high tension cable came off the ignition coil. Replaced it, and she fired right up. Unfortunately, the battery wasn't charging though, and it turned out the alternator's time had come. After a $120 charge to rebuild it, I was sorted.

 

[duaneb9729]

glad you got it fixed falcon! good job!

 

[Tosh]

So what do you suppose made the loud bang?

 

[Falcon_LS]

I suppose the bang was the cable coming off the ignition coil.

 

[meep]

so--- is your TB overdue?? I've never heard of one failing early... and since you thought it could be the TB.... ???

 

[Falcon_LS]

The timing belt is at it's "half life" so to speak. I change it every 50,000 miles, and it's currently at the 25,000 mark.

That said, there is one thing I noticed after I sorted this problem out. When the engine is cold, and you give it some gas, the rpm drops and then goes up. It's as if the engine died, and came back to life with a higher rpm. Could these be spark plugs by any chance?

My distributor rotor, cap and ignition cables have 32,000 km (20,000 miles) on them and the spark plugs (NGK BPR6E-11) have 19,000 km (12,000 miles) on them.

 

[Rooy]

Originally Posted By: Falcon_LS
I suppose the bang was the cable coming off the ignition coil.


I had this happen once. Driving along, loud bang (like a firecracker), engine dies.

The coil wire had blown out of the distributor cap. Also burned part of the cap.

My best guess as to what happened in my case is that the wire was not pushed in all the way, it arc'd and maybe ignited some oil that had been dripped onto the connection.