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  View original topic: Hydraulic Valve Sound on Deceleration
WendyArmbuster Wed Sep 17, 2014 3:59 pm

I have a '78 bus with hydraulic lifters, and on deceleration, even when changing gears, the valves (I'm assuming) sort of clatter. Not a bang bang bang like they haven't pumped up, but more like a rattling heat shield, or egg beaters on the side of a small piece of metal. All other times they are fine, and my bus makes good power. Is this a normal thing with hydraulic lifters? Does it indicate a need for adjustment?

Brian Z

busdaddy Wed Sep 17, 2014 4:39 pm

What's your oil pressure and endplay like?

WendyArmbuster Wed Sep 17, 2014 4:49 pm

I can tell you that my oil light is not on. I have not measured my endplay.

busdaddy Wed Sep 17, 2014 5:31 pm

I'm curious about the overall health and age of your engine.

Ian Wed Sep 17, 2014 5:40 pm

I've heard that noise before, it's a loose valve seat.

Pop your heads off and take the valves out, I guarantee one or more seat is loose.

Later.

raygreenwood Wed Sep 17, 2014 5:40 pm

busdaddy wrote: I'm curious about the overall health and age of your engine.

Yes....because it may not be the lifters at all. In the rare case where you totally lose thrust control on the rearmost cam bearing....it could be the, cam, shifting in the case and gear against pump rattle.
Remote....but not uncommon. Ray

WendyArmbuster Wed Sep 17, 2014 9:13 pm

So, the consensus here is that it's probably not an improperly adjusted valve, but imminent engine destruction?

It is an older engine with newer valve guides I bought from a dude, so it is a total unknown. I'm toodling around town with it (and currently commuting 70 miles round trip each day) while I gather parts for a proper engine. I can say it has 120 pounds of compression in all four cylinders. I have a hard time visualizing a loose valve seat hanging in there for the last year that I've been hearing this noise. Low oil pressure is a real possibility, but I don't currently have a way to check.

busdaddy Wed Sep 17, 2014 9:34 pm

Could be lots of things like loose seats or worn rod bearings, but it also could be something simple like a loose piece of tin or exhaust or a throttle body or decel valve failing in a strange way or even a loose engine mount or CV joint, don't go yanking the engine until you've explored all the other possibilities but in the end brace yourself for the worst.

Start by pinpointing exactly what condition does it and what doesn't.

airschooled Wed Sep 17, 2014 10:18 pm

busdaddy wrote: Could be lots of things like loose seats or worn rod bearings, but it also could be something simple like a loose piece of tin or exhaust or a throttle body or decel valve failing in a strange way or even a loose engine mount or CV joint, don't go yanking the engine until you've explored all the other possibilities but in the end brace yourself for the worst.

Exactly- try for a solution in common and easy problems first. Don't go for the most difficult or expensive repair until you've tried the free and simple fixes. Last week I thought I had a CV going out, but it turns out I hadn't tightened my shock all the way after removing it the day before.

Good luck,
Robbie

Ian Thu Sep 18, 2014 4:18 pm

It's definitely a loose valve seat.

I should have recorded the noise that motor made, I'll start doing that in the future since my other hobby is recording sounds. It had great power and compression was fine but it had a rattle on decel that sounded exactly like a loose heat shield. I replaced the head with the bad valve seat and everything's been hunky dory ever since.


Manfreds78bay Fri Sep 19, 2014 11:30 am

Ian wrote: It's definitely a loose valve seat.

I should have recorded the noise that motor made, I'll start doing that in the future since my other hobby is recording sounds. It had great power and compression was fine but it had a rattle on decel that sounded exactly like a loose heat shield. I replaced the head with the bad valve seat and everything's been hunky dory ever since.]

I'd like to hear that! I have a noise similar to what you are describing. It would go away after warm up. But I recently adjusted my valves and it doesn't anymore. I'm thinking I just need to dial in my adjustment better.

Did the noise just start out of no where? Does it quiet down? Can you hear it at start up or only on deceleration?

WendyArmbuster Sun Nov 02, 2014 4:14 pm

Solved! When I went to hook up my heating system for the season I noticed that my right heat exchanger was loose. I tightened it down with a hose clamp, and bam! Problem solved.

timvw7476 Sun Nov 02, 2014 6:54 pm

now i'm confused, was it the muffler to mount connection that got set right
with a hose clamp? i can't visualize a heat exchanger set right with a hose
clamp.......of any size.

raygreenwood Sun Nov 02, 2014 7:42 pm

WendyArmbuster wrote: Solved! When I went to hook up my heating system for the season I noticed that my right heat exchanger was loose. I tightened it down with a hose clamp, and bam! Problem solved.

The sheet metal around the actual header pipes was rattling. ....right? Glad you found it!

Engine destruction is still eminent...... :lol:

Ray

WendyArmbuster Sun Nov 02, 2014 8:01 pm

It was tricky to fix with a hose clamp. The entire front of the heat exchanger would move up and down on the header, so I put a hose clamp around the hot air exit (which would normally have a flapper valve clamped to it, but I have a flexible aluminum duct going straight to the rear under-seat Westy vent) and positioned the screw housing so that when I tightened it it pushed itself up against a triangle flange, wedging itself tight and preventing a rattle. I expect it to fail to prevent rattling after a few heat cycles, and I will have to think of something new.

On that note, I have one of the heat exchangers feeding that rear vent, and the other feeding the defrost/foot vent. It seems to keep the bus warmer overall, but man is it puny defrost. It definitely blew to the front harder with both exchangers.

Wildthings Sun Nov 02, 2014 8:22 pm

WendyArmbuster wrote: It was tricky to fix with a hose clamp. The entire front of the heat exchanger would move up and down on the header, so I put a hose clamp around the hot air exit (which would normally have a flapper valve clamped to it, but I have a flexible aluminum duct going straight to the rear under-seat Westy vent) and positioned the screw housing so that when I tightened it it pushed itself up against a triangle flange, wedging itself tight and preventing a rattle. I expect it to fail to prevent rattling after a few heat cycles, and I will have to think of something new.

On that note, I have one of the heat exchangers feeding that rear vent, and the other feeding the defrost/foot vent. It seems to keep the bus warmer overall, but man is it puny defrost. It definitely blew to the front harder with both exchangers.

Add a booster fan of some sort up front and you will be set. I need the fan to be on around town, but on the highway am in general fine with it being off even when the temps are in the twenties.



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