Info needed: Strange Sound

[Phil Waterman]

Hi All

Was taking the truck out to play in the snow this morning. HUP started right up after sitting for a month in cold ranging from 0.3/56 F or -17/13 C. Stock 216 cu.in. full rebuild a couple of years ago. Since then every now and then I'll get this sound on starting when the temperature are well below freezing only last a couple of seconds.

This time I had the GoPro Camera with head mount turned on the clip shows the entire start sequence accept that the electric fuel pump was on for about 30 seconds before I hit the starter. That is the full cranking time. You can see my head turn looking for the noise. Sound comes 44 seconds into the video.

Oil pressure had already come up to 25 PSI by the time the sound occurs.

Clutch is disengaged and the trans mission is in neutral.

Any thoughts?

Added a short video of the short ride later.

Cheers Phil




https://youtu.be/rVMBXy9ImZ8

Video of drive https://youtu.be/kbqcGDFRPVc

[Wayne Hingley]

Phil, that is indeed a strange noise. Sounds like someone knocking on the door wanting to go for a ride with you.

It sounds something like "water hammer", could it be some type of "thermal expansion" that occurs for a couple of seconds as things warm up? Im thinking something like an exhaust hanger, exhaust pipe, or something like that?? It happens about 40 seconds after the engine is running, so the gasses would just be starting to get hot and transferring energy into the surrounding metal.

It would be good to do another cold start when you are in position and able to get under the truck and observe/listen closely.

Good luck!

[David Dunlop]

You haven't got a resident squirrel trying to keep his nuts from overheating do you. Phil?

Love the drive clip. Looks like you were on the way to cover the Battle of the Bulge!


David

[Phil Waterman]

Hi Wayne and David

Wayne your idea of the sound being a expansion sound as the exhaust pipe expands might have some merit and had never occurred to me. The exhaust pipe is bolted down solid at manifold, muffler and tail pipe with no kind of flex mount that might also explain why this is a sometimes occurring.

The noise does seem to come from the left side of the truck.

Combining the two theories it might be the squirrels banging on the pipe for more heat. I have had problems with squirrels filling the muffler with nuts but the nuts make more of a wooden sound as they fly out of the pipe and with the wall of the garage. An the squirrels make more of a puff spat as they are blown out of the pipe.

Going back years did have mice take out the clutch of the HUP one winter they built a nest on top of the throw-out bearing shaft I pushed the clutch in as I started the engine and the nest material flew out into the fingers of the clutch which from fully engaging. Since then if the truck has been sitting for a long time I put the truck in neutral and turn the engine over a couple of times to dislodge any possible nest. After a couple of revolutions I push the clutch in to help speed the turn over.

Bob has suggested that it might be that the gear lube is draining out of the upper gear cluster making the cage bearing bank around till the lube is splashing around. I've always wonder how much the gear lube is flying around the inside of the case when the transmission is in 4th gear.

Bob might be right I have had the shaft area for the cage bearing pit. But that noise was always there. Just as when I broke a gear tooth noise was always there.

It is just one of those noises that as it is inconsistent is hard to find until something really breaks.

If you turn up the volume before playing the video you can hear the waa sound from the choke as the engine first starts. Wonder if this over choking issue one of the reasons that the later Pattern 12 have the choke on the right side of the steering shaft so that you can have the right hand on the choke while the left is pulling up on the starter.

The noise I'm talking about comes about 44 seconds into the video.

Thought that this long range diagnostics would be interesting to try particularly as sound came out so clear on the video.

Cheers Phil

[rob love]

Originally Posted by Phil Waterman

Bob has suggested that it might be that the gear lube is draining out of the upper gear cluster making the cage bearing bank around till the lube is splashing around. I've always wonder how much the gear lube is flying around the inside of the case when the transmission is in 4th gear.


Cheers Phil

In any standard transmission I ever worked on, the countershaft is always turning, no matter what gear you go into. If you want to find out how much oil splashes around, even at idle, pull the floorplate and the shift tower off. I would suggest wearing goggles though.