Knock at idle

[CopenGrizz01]

I just bought a 2005 murcury mountaineer with the 4.6l v8. It has 139000 miles and runs and drives great. I love it. When I went to check it out and test drive it this knock was not present. After I bought it I drove it home which was about an hour drive. Parked it in the driveway and heard a knock. It only knocks at idle if I give it a little gas it goes away. It's not a rattle or tapping it's a knock. It does this all the time now. I'm afraid its a rod knock but wanted to ask you guys what you think. If your standing directly over the engine you can't really hear it but if you step back by the drivers door it's pretty loud. So I don't think it's coming from the top end. The engine is very clean no leaks at all it runs perfect not even a hicup. I can make a video of the noise if you all would like to hear it. I'm just really hoping it's not a rod knock. Oil pressure gauge is always right at half so I'm guessing oil pressure is fine unless the gauge dosnt work right. Also sometimes on a cold start the knock isn't there for about 30 seconds then in appears again and when it's somewhat warm out you can hear the knock up to about 1500 rpm and the knock increases with the rpm but then fades away. Thanks for any help.

 

[Joe in NY]

Don't even bother with oil gauge.. It only means you have over 5 psi.. When our motor started to fail in our suburban the oil pressure dropped from it's normal 40+ psi down to 10 psi. This told me the Displacement on Demand controller failed.. And it did. However if it had been a ford, I would never have known and it would say "Perfect!" Don't rely on ford dash. It sucks. Temp only goes hot after you overheat the crap out of it too...

Hope you get the noise figured out!

 

[CopenGrizz01]

Also I just noticed that if I turn the key to the on position but not started the check gage light comes on then it says low oil pressure in the mesage center. It does not say this while it is running.

 

[Joe in NY]

because when the engine isn't running there is no oil pressure... What is your point?

 

[Number4]

because when the engine isn't running there is no oil pressure... What is your point?

Joe, Joe, Joe.......Joe. he's new to the Explorer. I know you aren't from the Bronx, because you say 'NY' so play nice.

As Joe said, you have no oil pressure because the engines off and you have the system in the run position, it's just not running.

The knocking could be from the torque converter, I believe there was a post about this recently. I think it was locking up at idle. Just an idea.

 

[Joe in NY]

Joe, Joe, Joe.......Joe. he's new to the Explorer. I know you aren't from the Bronx, because you say 'NY' so play nice.

As Joe said, you have no oil pressure because the engines off and you have the system in the run position, it's just not running.

The knocking could be from the torque converter, I believe there was a post about this recently. I think it was locking up at idle. Just an idea.

What.. So the knocking torque converter failure is the TQ trying to lock up? Or do they also break up inside?

 

[Number4]

This isn't the post I'm thinking of. But it's similar, skip down to post #6 . The one I'm remembering, the guy had recently put in a TC. He then got this noise so he removed the trans and said the TC was locked up. I want to say the engine was trying to stall too.

http://www.explorerforum.com/forums/showthread.php?t=427165

Mine on occasion makes a rotational knocking sound. Also sounds like it's from the trans area. Almost like the flex plate is hitting something.

 

[BarryCarey]

This isn't the post I'm thinking of. But it's similar, skip down to post #6 . The one I'm remembering, the guy had recently put in a TC. He then got this noise so he removed the trans and said the TC was locked up. I want to say the engine was trying to stall too.

http://www.explorerforum.com/forums/showthread.php?t=427165

Mine on occasion makes a rotational knocking sound. Also sounds like it's from the trans area. Almost like the flex plate is hitting something.

It was the TC in my case. Just got it fixed 2 weeks ago. My wallet wasn't thrilled with the bill.

OP, get under it when it's running. You should be able to tell if it's coming from the Oil Pan or Bell Housing.

 

[CopenGrizz01]

I looked up on YouTube what a cracked flex plate can sound like and a couple videos sounded just like my knock. It's raining right now so I'll have to wait till its dry out before I climb under it. My knock definitely sounds rotational and its very consistent. No rattle or clunking just a knock.

 

[Green98XLT]

My 02 Ex with the 4.6 does it too, its from the torque converter I'm almost certain. Does yours have the growl when accelerating that goes away when the converter locks up in 4th or 5th gear? These things had notorious converter issues but in spite of the noise they seem to last and run just fine.

 

[2000StreetRod]

If not the torque converter

I don't want to scare you but in my opinion the 4.6L has a susceptibility to spinning rod bearings. The backing of the bearing is not designed to sustain rotation and wears rapidly when it occurs. I purchased a block from a shop that replaced the original Aviator engine due to a knock. When I tore it down I found two spun rod bearings and the crank and two rods were unserviceable.

Hopefully, your knock is not due to a spun bearing.

 

[CopenGrizz01]

I crawled under it today and I believe the knock is coming from the engine. I couldn't hear anything from the bell housing. I used a screw driver to try to listen but couldn't really hear the knock from the oil pan but I do believe it's coming from the engine. I'm guessing a spun rod bearing. Really sucks since I just bought the thing and it only has 139000 miles. And I definitely don't have the money right now to get it fixed. Hopefully it'll be fine till around march I have no choice but to drive it it's my only vehicle.

 

[turborich]

Is it louder at start up and then quiet down some after a minute or so? If so check for an exhaust manifold leak from a broken stud. Sometimes this sound will fool people.

As far as the post about the 4.6 being prone to spun main bearings, Yes it could be a bearing but just so you know, the 4.6 is a long lived engine when properly maintained. Taxi's, police cars, F-150's, etc use the 4.6. I don't think they are any more likely to have this problem vs any other engine. The 4.6 is a stout engine.

If you want to check oil pressure then go to Harbor Freight or Autozone and pick up a cheap manual gauge, screw it into where the sending unit is at, start the engine and run until at normal operating temp to verify oil psi. Look up the specs for your engine and RPM's.

Take a video and upload to youtube, someone may be able to point you in the right direction.

 

[CopenGrizz01]

Starting to think it could be the flex plate. Yesterday I went to start it and the starter acted like it couldn't engage it was just grinding so I quit and tried again and it started fine and then today it did the same thing. So I'm thinking the flex plate could be cracked or loose. But I couldn't hear the knock coming from the bell housing when I was under it. But I also couldn't hear it from the oil pan. It's easiest to hear from the drivers side and pretty loud in the wheel well. I'll post a video here in a few so you guys can actually hear it.

 

[CopenGrizz01]

Alright here's a video of the knock and also I showed the oil pressure gauge which never changes unless the car is off of course.
https://youtu.be/KPwv8hRQ8jk

 

[ScaryWoody]

I would do a Seafoam treatment and add Lucas Oil treatment. If that doesn't help here's a video that may be helpful https://www.youtube.com/watch?v=pYleKxjl0uY

 

[Number4]

When's the last time you did an oil change? If it's rod knock, you should have metal flakes in the oil, like glitter.

 

[CopenGrizz01]

I haven't changed the oil I just bought it like a week ago. I do plan on changing it soon to see if there's any metal flakes in it. I crawled under it again today and it's really hard to tell where it's coming from. It kind of sounds like the bell housing like on the top of it but it also sounds like it could be coming from the engine.

 

[Green98XLT]

I'd do an oil change first and use a quality 5W30 with a MOTORCRAFT FL820S filter and see what that gets you.

 

[CopenGrizz01]

Just changed the oil. Put 10w30 valvaline max life in it with Lucas oil treatment. And the knock hasn't changed at all if anything it might be a little louder now but that could just be me. I didn't find anything in the old oil it was actually pretty clean not dark or anything.