Strange engine noise (1 Viewer)

[Plantman]

I've got a 1997 LX450 with 308000 on the clock and about three weeks it developed a knocking/ticking noise. At first I thought it was an exhaust leak (I've heard it's common for the '95-'97 to develop a leak in the down pipe), but as I started looking and listening for an exhaust leak, with a friend running the throttle, I became less convinced about it being exhaust. It makes the noise when the engine is up to normal operating temp and increases with RPM. It is a little louder when the engine is under load.

I searched the forum and found ideas about bad valves, loose spark plugs, pinging due to over-advanced timing, etc. I advanced my timing 5 years ago and never had any pinging issues (I run 87 octane as recommended by Mr. T).

Any ideas as to what it could be and how to fix it. Am I good to drive a couple hundred miles home before I fix it?




-Chance

 

[Formulaonehd]

Definitely need a video or sound recording. Best way to get the video is to upload it to your youtube account and then paste the link onto here.

 

[Plantman]

You can hear it pretty well in this video.

 

[Formulaonehd]

I reckon its your valves after hearing that

 

[BILT4ME]

I would still say exhaust.

 

[mingles]

Did you check the "Y" pipe to exhaust manifold studs and nuts?

I had a similar sound and that was my culprit. With that connection loose, the donut gasket burned through and even re-tightening wouldn't do away with the leak. New gaskets and it was gone. Especially with the heat shields still in place, that leak is hard to spot or feel.

 

[Plantman]

Did you check the "Y" pipe to exhaust manifold studs and nuts?

I had a similar sound and that was my culprit. With that connection loose, the donut gasket burned through and even re-tightening wouldn't do away with the leak. New gaskets and it was gone. Especially with the heat shields still in place, that leak is hard to spot or feel.

That would make sense, checked in those spots with he heat shields off, but I didn't find anything by looking and I didn't have access to any deep well sockets to actually get on the nuts see if they're tight. I'll see if I can do that sometime this week.
Thanks

 

[Jgrauman]

That would make sense, checked in those spots with he heat shields off, but I didn't find anything by looking and I didn't have access to any deep well sockets to actually get on the nuts see if they're tight. I'll see if I can do that sometime this week.
Thanks

If you have a shop vac or blower, tape it to the exhaust pipe (cold exhaust) blow air into pipe, spray all gaskets/welds/connections with soapy water... Easiest way to find an exhaust leak

 

[Formulaonehd]

Its sounds pretty metallic as a knock (just from the video) if it is an exhaust leak wouldnt it be more of an airy fart noise or if theres some broken crud in the cat its more of a 'ding a ling' xmas bell noise from my exp

 

[nukegoat]

It sounds broken

 

[Tooth Fairy]

Haha!

 

[Tooth Fairy]

If it is one of the exhaust donuts I’ve got some.

It sounds like an exhaust leak to me and I’ve heard it first hand. I like jgrauman’s plan.

 

[Plantman]

It sounds broken

Haha!
Thanks man.

I’ll give jgrauman’s test a shot and see what happens.

 

[Formulaonehd]

It sounds broken

My first instinct was a HG but i cant see any milky discharge on the climb up the hill

 

[Plantman]

My first instinct was a HG but i cant see any milky discharge on the climb up the hill

I didn’t see any gray sludge in the oil cap, but I haven’t checked the radiator cap in a while, but it’s never overheated and it runs at the normal temp still.

 

[Plantman]

Found a loose nut on one of the studs holding the exhaust manifold on at cylinder number 4. I tightened it and the sound is quieter, but not gone. Ordered a new gasket that should be in tomorrow and I imagine that will solve that problem.

(No gray sludge in the oil or radiator caps.)


Anybody ever had an exhaust manifold heat shield crack?

 

[Tedward]

I recently replaced exhaust. One of the two exhaust manifold heat shields was cracked. Not all the way across. About an inch or so in 2 directions starting at one of the bolt holes. I don't know if it made noise or not. I did have some exhaust rattle that was metallic sounding rattle at certain times at idle.
Gone now but was missing a hanger too.

 

[SmokingRocks]

I'm with @Formulaonehd it does sound like rod knock. But it's hard to tell in that video, perhaps you can get just a video at idle from under the hood and rev it some.

 

[Formulaonehd]

Found a loose nut on one of the studs holding the exhaust manifold on at cylinder number 4. I tightened it and the sound is quieter, but not gone. Ordered a new gasket that should be in tomorrow and I imagine that will solve that problem.

(No gray sludge in the oil or radiator caps.)


Anybody ever had an exhaust manifold heat shield crack?

Loose manifold nut> Jeez those things are practically welded on, someone didnt torque them properly

 

[SmokingRocks]

A trick I use to locate exhaust and intake vacuum leaks is to make my own stethoscope.

Get about 4’ of vacuum hose, wedge one end in your ear and put on some hearing protection / headphones. Then take the other end of the tube and touch it around suspect areas.

You will know when you found the leak when you clearly hear it.