Hello everyone, I have a 1999 Mazda B4000 4.0L v6, and there is a fluttering sound coming from somewhere in the engine. I'm thinking it might be the timing chain. Before I get into this project, I was wondering if my engine was interference or non-interference? I found a list online: AGCO Automotive Repair Service - Baton Rouge, LA - List Of Interference Engines but it doesn't include the 4.0L engines. I called Mazda and they told me it was non-interference, which is good news, but from searching this forum, people have heard different things. Does anyone have a concrete idea or a solid source for this information?
Also, does anyone have any suggestions as to what that fluttering sound could be? It is loud when I start up the engine, then it lessens as I drive. Thanks!

 

Found a good read, with the info of it being non-interference: Ford 4.0L V6 Engine - Explorer, SOHC, Timing Chain

 

4.0l OHV, 1990 to 2000 in Rangers/Mazda B-4000 is a non-interference engine, 9.0:1 compression ratio

4.0l SOHC, 2001 to 2012 in Rangers/Mazda B-4000 IS an interference engine, 9.7:1 compression ratio
So that article is incorrect in regards to the 4.0l SOHC, if you look you can find pictures of SOHC pistons that were damaged by valve strikes, and valves of course were bent
BUT............because there is not that much overlap in shared space the engine is usually running so poorly from loose/slipped timing chain that valve damage doesn't occur, but it FOR SURE can occur, 4.0l SOHC is an interference engine 100%

This is where confusion comes from when looking at Ford 4.0l engines

If you look at higher compression ratios, above 9.5:1, they will usually always be interference engines

 

Ah, I gotchya. Thank you. Well that makes me feel a little better about the timing chain being an issue. I have a 99 Mazda 4.0L. I would still rather replace it before it fails and leaves me stranded, but it's good to know that it won't decimate my engine. Thank you.

 

Timing chain is an odd failure on the 4.0l OHV

Yours would be the first I have read about, people do change them on a rebuild just never read about even a tensioner failing

 

What else would make a flutter sound, if not the chain? It sounds like it's coming from the back/bottom of the engine near where the transmission meets it. The best way I can describe the sound would be if you hold a screwdriver out so that it hits the fan.

 

Timing chain on the 4.0l OHV is behind the water pump, front of the engine.

Could it be coming from the bell housing, manual or automatic?

Starter motor gear is not being pulled back all the way?

 

It could be, it sounds like it's from that area, it's just really loud, which makes me think it's not inside the housing, but it very well could be. It's an auto. I can hear the starter when it starts up, next time I'll listen for a break between the two sounds.

 

Should be able to remove the inspection plate on bell housing and see if ring gear has marks.
Also BLOCK THE WHEELS, Unplug the Coil Pack(NO START), and have someone turn over the engine, check each torque converter bolt, 4 I think, on the flex plate, one could have backed out and is hitting

 

So we took a closer look at the truck, my buddy said it sounded like the valves sticking. Apparently in my original diagnoses I didn't check my fluids. There was about 1 quart of oil in my engine. The back of one of the valve covers had a very loose bolt. Tightened that up and I haven't lost any oil, and that was 300 miles ago.