DupermanDave

I'm going to post a video later when it's not too windy out. Here's whats going on. after work
today my truck started making a bad ticl/tap/knock at idle. the noise isn't noticeable when
driving. i believe it started, just not as bad, a few days ago when i drove the truck hard in fast
lunch hour traffic. the sound is coming from what sounds like the #1 spark plug and could be
coming from the valve cover. i used seafoam to see if i could find an exhause leak, and i found one
down the pipe, but not where the sound is coming from. the leak is where the manifold joins the
exhaust pipe and it's big enough the seaform started seaping out.
i say it's a tap/knock because it's a little of both. it doesnt seem to be affecting the performance
at all, but it does sound bad. if this was a rod knock or anything serious, what would i expect to
see/hear/and feel?
i will say this much, but don't want it to bias any diagnosis. i had a few stripped threads during a
headgasket install that we fixed, but one or two remain stripped. also, i did some urban off-
roading and went over the median in the parking lot at work and that was bumpy. yesterday i also
replaced the parking brake cable.

2DoorRunner

The crack in the downpipe is pretty common i have heard.
It sounds like you have timing chain noise. Is there more noise on start up? And since you say it goes away when driving, it sure sounds like the timing chain to me.

2DoorRunner

A trick my dad taught me, use a long screw driver to pinpoint where its coming from. Hold the screw driver on the valve cover and hold your ear on the end of it, it can tell you where, and what it is.

DeathCougar

iTrader: (23)

Rod knocks are usually pretty detectable. Sounds about like someone threw a handful of marbles into your engine.

DupermanDave

i thought it could be the timing chain too, and im going to get right on that when i order the performance 268 cam. but i went on youtube and did some searching and it doesnt sound as metallic as a timing chain. still, i wouldnt rule it out.

modlite

From my experience with rod knocks on my truck, when you rev it to about 2800rpm is when it starts to get really noticeable and worse.

2DoorRunner

I have injector noise, valve noise, timing chain noise, and after hearing that i might have rod knock noise too lol.

DupermanDave

i'd also not suspect the timing chain because if i had to narrow down a location on the valve train (left, center, right) i'd have to say it's definitely more noticable on the exhaust side. i thought it could be a spark plug knock so i unplugged plug wire 1 and 2 individually and it didnt go away.

85gijunk4x4

check to make sure all the sparkplugs are tight

DupermanDave

I got some great helpfull bits of information. I started up the truck when it was cold this morning and the noise was gone. After I got closer and closer to work, it became more apparent. I got to work and it was sounding like a diesel again. I got video of the cold start and the hot engine after work, so you can listen and compare. I'll post them in a few hours after work.

Checked the sparkplugs this morning, but I may take them out again and chase the threads to #2, 3, and 4 just for the heck of it. I already did the #1 hole.

Now that I listen to the noise more, it seems to be coming from the back of the engine. I guess it sounded like the front because of the noise echoing from the hood.

DeathCougar

iTrader: (23)

Rod knocks and timing chains are usually present at all times. Exhaust leaks may not show up until the truck is warm, since heat expands the metals and opens the leak gap.

DupermanDave

Here are both videos, one of the engine cold and one after it has warmed up from the drive to work.

During the cold start, you'll hear the belt squealing (need to fix that) but if you listen carefully you won't hear as much of a knock. The smoke from the cold startup is just some seafoam leftover from last night. The smoke isn't blowing out the exhaust manifold, just the downstream crack.

http://www.youtube.com/watch?v=Rm2NmHljFlo

http://www.youtube.com/watch?v=-pyjQavaheU

pruney81

That sounds like and exhaust leak to me. My old 87 had a really bad leak at the manifold when I bought it and it was terribly loud

2DoorRunner

Like i said, you could have used a screwdriver as a stethoscope to pin point the noise.

But after looking at the videos, i would say exhaust leak, the hot metal expanding to make it worse and louder. Timing chain would have been apparent at cold start too. Same with valves.

Keep in mind i have never heard a bad rod knock, so i am going off others experiences with that. But i HAVE heard exhaust leaks

ohgood

exhaust leak.

casting is cold = small leak
casting is hot = big leak, more noise

cool thing is, it's nothing to worry about. keep on truckin

DupermanDave

I've used the screwdriver technique in the past, but on this occasion it was really hard to pinpoint the location of the noise. I've used this technique in the past, though, on finding ticks in the fuel injectors.

Since it's an exhaust leak I won't worry too much about it, but I will be getting those stripped studs fixed now that summer has arrived. Maybe I'll get some headers too instead of patching that downstream leak.

DeathCougar

iTrader: (23)

this is incorrect.

While a small exhaust leak may not cause any problems, larger leaks can and will cause problems ranging from burned valves, to bad O2 sensors and overheated cats.

In a typical passenger car/truck, a small leak isn't too detrimental. You should still fix the issue if nothing else for the annoying sound it makes.

DupermanDave

Great. Now you've got me scared. I've got to live with this for at least another 2 weeks while the engine is out of our other car.

pruney81

I wouldn't worry about it. If you had a 3vze that might be different story. A little exhaust leak can't hurt these engines.

DupermanDave

I already had the seafoam leftover from a few months ago. I had it sitting under my seat and it had about 1/3 of a can left, so I just poured that in the brake booster line.