Knock in engine

crom9111 · #1 11-02-2012, 04:50 PM

Hi all, I was coming of an on ramp today and had what sounds like a nasty push rod knock start. Very loud coming from under the front side valve cover. Sorry this is a 95 windstar with the 3.8. Had the van towed home, pulled off the valve covers and at least the springs look good and the rods are all true. My question is, could a collapsed lifter make that much noise. it is very loud. Again it sounds just a bent rod but they are all good. Any help or ideas would be greatly appreciated. Thanks

tempfixit · #2 11-02-2012, 08:41 PM

Quote:

Originally Posted by crom9111

Hi all, I was coming of an on ramp today and had what sounds like a nasty push rod knock start. Very loud coming from under the front side valve cover. Sorry this is a 95 windstar with the 3.8. Had the van towed home, pulled off the valve covers and at least the springs look good and the rods are all true. My question is, could a collapsed lifter make that much noise. it is very loud. Again it sounds just a bent rod but they are all good. Any help or ideas would be greatly appreciated. Thanks

A colasped lifter would let the push rod become loose on the tappet and cause a loose tappet sound.

Can you by chance do a video with sound and post it here so we can listen to it and possibly help you diagnose problem.

How did the engine run when this occured?? Missing???

Have you checked the camshaft sensor and snycronizer condition as it is located on the front of the engine (passenger side) middle.

Is the check engine light on??? if so what are the codes???

Did the idiot light for oil pressure come on??

crom9111 · #3 11-02-2012, 09:58 PM

Sorry but already have a lot of the top end dis assembled

so no sound. It sounds like a tappet sound if you amplified it a lot. It's really loud. It is rhythmic i.e it is in time with engine speed. I changed the oil just 3 days ago at its usual 3000 miles. No engine codes ( hard or soft ) and no other indications of a problem. As a kid I bent many a rod in my 350s from over reving them and it is a similar sound just louder. I've had valves not pump up until you increased the rpms but the sound now just gets louder. I guess my concern is, would a problem on the bottom end transfer that much sound to the top. I plan on getting the lifters out tomorrow and if that doesn't lead anywhere then I guess check the rod bearings. Is there a way a valve could break at the "flange" and cause the noise?

tempfixit · #4 11-03-2012, 12:30 AM

Quote:

Originally Posted by crom9111

Sorry but already have a lot of the top end dis assembled

so no sound. It sounds like a tappet sound if you amplified it a lot. It's really loud. It is rhythmic i.e it is in time with engine speed. I changed the oil just 3 days ago at its usual 3000 miles. No engine codes ( hard or soft ) and no other indications of a problem. As a kid I bent many a rod in my 350s from over reving them and it is a similar sound just louder. I've had valves not pump up until you increased the rpms but the sound now just gets louder. I guess my concern is, would a problem on the bottom end transfer that much sound to the top. I plan on getting the lifters out tomorrow and if that doesn't lead anywhere then I guess check the rod bearings. Is there a way a valve could break at the "flange" and cause the noise?

In my opinion a bearing knock is a little different than a tappet sound and I would think a broken valve would cause a hole in the piston. How do the spark plugs look, any beat up??? I would say yes that the sound could migrate to the top end.

Let us know what you find.

Good luck

12Ounce · #5 11-03-2012, 08:21 AM

The 3.8 has three likely noise makers that I know of:

Top of the list is a plastic inner piece of the upper intake manifold that can come a bit loose and rattle ... I've never heard it myself, but understand it sounds very metallic.

Much rarer is a broken cam chain adjuster/tensioner. Let's the chain slap!

And yes, lifter springs have been known to break. I've never experience any or these (knock on wood!).

crom9111 · #6 11-03-2012, 09:47 AM

After watching countless videos on You Tube ( I love the internet lol ) based on sound alone it sounds like a rod knock. So getting ready to drop the oil pan to check the bearings out. If they prove good then back to the top end I guess. The thing that is throwing me is it sounds like it's right under the valve cover.

crom9111 · #7 11-03-2012, 04:11 PM

Well pulled off the oil pan ( which had a hole in it, not a good sign ) and was looking at a twisted piece of metal that was my connecting rod. So now the debate is if I can just replace that 1 rod and piston and keep it going for a little while longer. All other bearings seem to be fine, no play in them. May just replace the bearings any how. Does this seem feasible to anyone? Unfortunately I do not have the money for a rebuild or rebuilt engine. I can get 1 from the junk yard for a couple hundred dollars with no guarantee it will work. Any input is appreciated

tempfixit · #8 11-03-2012, 04:35 PM

Quote:

Originally Posted by crom9111

Well pulled off the oil pan ( which had a hole in it, not a good sign ) and was looking at a twisted piece of metal that was my connecting rod. So now the debate is if I can just replace that 1 rod and piston and keep it going for a little while longer. All other bearings seem to be fine, no play in them. May just replace the bearings any how. Does this seem feasible to anyone? Unfortunately I do not have the money for a rebuild or rebuilt engine. I can get 1 from the junk yard for a couple hundred dollars with no guarantee it will work. Any input is appreciated

Have you removed the rod cap and inspected the crankshaft?? I would say the crank is also bad if there were parts of a bearing in the pan and a hole in the pan.

You are probably looking at a different engine installation.

crom9111 · #9 11-03-2012, 06:58 PM

Pulled the rod ends off and crank looks wonderful :0 bearings didn't look bad either. From what I can see of the cylinder from underneath, it doesn't look bad. I have to get the valve cover off of the back side or the engine in the morning.( just pulled the front side so far since that is where I thought the sound was coming from. If valve train is good on that side then I will try to replace the piston etc. with the engine still in the van. Even if it just gets me a few thousand more miles I will be happy

kevink1955 · #10 11-03-2012, 08:17 PM

Are you saying the rod broke in the middle and the bottom end was still on the crankshaft and it protected the crank?? If so and the crank looks good go for it, you went this far already.

crom9111 · #11 11-03-2012, 08:37 PM

Yes the rod broke mid way. If I could figure out how to post pics I would. Still curious to see why it happened. I would think if it dropped a valve it would just crush it since it is weaker then the piston/rod assy. Can a piston just seize? It could have filled with water i guess but it was running great at the time and that would have to be a hell of a leak into the cylinder

tempfixit · #12 11-03-2012, 08:56 PM

Did you ever notice any piston slap at start up??? Does the rod show any blueish color to it. Once the head is removed, hopefully you will find the cause of problem.

The only reason I can think of that a piston would sieze would be that a keeper on the piston failed and the risk pin slide out of one side of the piston and pin hit clyinder wall.

PS: Have you tried photobucket to post the pics???

crom9111 · #13 11-03-2012, 09:02 PM

No noises at all. The only noise the van made was from a small exhaust leak at the Y - flex pipe connection. Had the tranny replace 5 yrs ago and other then that it has been basically trouble free. I will check on photo bucket to post pics of the tear down tomorrow

12Ounce · #14 11-04-2012, 03:56 AM

I would definitely remove the heads to have a look on the top-side.

crom9111 · #15 11-04-2012, 02:55 PM

Got the heads off, piston and remainder of the rod out. A few marks on the top of the piston from where a valve made very light contact. valves are all straight and there, piston slid right out once the head was removed and head gaskets looks great. Other then the fact I had a connecting rod broke in half there looks to be no issues.....boggled

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