Tapping engine

scot

Well-known member
Sep 12, 2004
96
0
I posted a while ago asking about a tapping engine. The suggestion was to check out the rockers and verify they were secured properly etc. Everything checked out, and there was virtually no sludge in there. I did pull the pushrods out and they looked ok, a bit dirty so I cleaned them up, but nothing bad. Well within expectations for 86k miles.

The tapping/knocking sound seems to be a single tap per revolution or so (hard to say), and only under load which makes it very hard to narrow down to a specific location. Idle is fine and engine revs freely. It is audible at very slow speeds (1-15mph) and either goes away or is just drowned out by higher rpm driving. Does not burn any oil and the coolent levels are steady.

I just drove 1000 miles pulling a trailer (800-900lbs) a few weeks ago two weeks ago through the mountains. Other than having to drop a gear to maintain 75mph going up some very steep grades, it went splendidly. Gas usage came in at about 15mpg with the trailer.

Anyone have any ideas?

Scot
 

jhmover

Well-known member
Apr 23, 2004
5,571
3
California
What year Disco? They had a recall on some of the D-2s regarding valve train noise. If I remember it was replacing the rocker arm assembly. I had mine done on warranty. I wonder if this could be the problem?

JH
 
K

Kyle

Guest
A single tap per revolution ? Exhaust leak at the head or head pipe...
 
H

Hokie_Rover

Guest
"That's okay ... my morse code is so rusty I could be sending him the dimensions of this month's playmate"
 

scot

Well-known member
Sep 12, 2004
96
0
Could very well be an exhaust leak. Definitely not leaking at idle as I have checked all around both of the manifold but it could be sneaking through on the drivers side under load. I had a leak on the passenger side and replaced the gaskets already so that side is fine. The manifold itself was in perfect shape with no cracks at all.

I'll try to take the drivers side manifold off next week to check. Hopefully it is just an old gasket, and not a cracked manifold. If it is cracked, are there any issues with just welding up the crack or is it better to get a new one? (mig, and v'ing out the crack)

It is a 96 D1 by the way.
 
S

syoung

Guest
one interesting side effect of using seafoam to clean the intake- it will then point out in smokey splendor where each and every exhaust leak is.
 

byurko

Member
Aug 30, 2004
19
0
Raleigh, NC
I had an Accord that developed a tapping noise just like what you describe.... Turned out that the spark plug was loose and not fully torqued.

Bryan
 

scot

Well-known member
Sep 12, 2004
96
0
Spark plugs are torqued properly. Seafoam helped me find the leaks on the passenger side, but didnt show anything on the driver side. (un)Fortunately now when I run seafoam it never gets smokey. Guess everything was blown out in the original 2-3 applications.


Though I will say, I think the people behind me that night were quite astonished at the smoke pouring out!

Scot
 

dhuddleson

Well-known member
Apr 21, 2004
128
0
Ottawa, Ontario, Canada
Have you tried using a stethescope to narrow down the source of the tapping sound??? It might help to determine if the sound is external (exhaust leak/crack) or internal. Hopefully it will not be the dropped liner as in my Disco last spring.... with a knocking sound once the engine warmed up!
 
D

Disco/here/Disco/there

Guest
Try the Servo Assist pump on the side of the engine as it caused the same problem for me and no one knew what it was until the servo brakes started to act up

Hugh
 
B

barefoot

Guest
all good advice above...my bets on an exhaust leak. make sure all the bolts are torqued down properly first. the ones on the pass side are a little harder to get to but if you havent checked them yet...the pressure could just be escaping under load. you may be able to see black exhaust marks on surrounding parts if you look closely.
 

Whitey

Member
Nov 11, 2005
7
0
I have the same suttle tap per rev. its sounds something mech not exhaust leak aswell. I have a 454 gmc 3500 dually with exhaust manifold leak(S) so I know what that sounds like. the servo check is good advicce that I will follow. Its def a knock seems to be once its warm. by the way mine is a 1998 disco 1 with 60,000 miles on it. great thread. good info guys... Thanks
 

Tree Trimmer

Well-known member
Apr 30, 2004
100
0
Foothills of NC
dhuddleson said:
Have you tried using a stethescope to narrow down the source of the tapping sound??? It might help to determine if the sound is external (exhaust leak/crack) or internal. Hopefully it will not be the dropped liner as in my Disco last spring.... with a knocking sound once the engine warmed up!
I saw my Father-in-Law (mechanic of many years) use a short wooden handle from broom, etc.. One end on various parts of the engine or ancilleries and the other against ear. Very cheap.