Chirp coming from 1700cc engine

1973 1700cc bus strange chirp coming from engine compartment

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sound sample uploaded.

first on the left side of engine then on the right side of engine, then from top of the engine compartment..

high pitched chirp alternating between left and right sides

I did some more listening to the engine.

#1)yes, it will run. #2)the sound (chirp, like vaccum or pressure) alternates between left/right of engine #3)the sound is eliminated from the **left** side of the engine when I remove the plugs from the **left** side

ok... sources of intake and exhaust from the sides of the engine:

1)balance tube for air. connects to "master" output on top of left side carb. connnects to top of left side manifold. connects to top of right side manifold

#2)"balance" tube for brake booster. this is at the base of each manifold, they are connected by metal tube. brake booster connects to this tube.

#3)EGR tube. EGR isn't connected (crimped off before it goes to exhaust). This connects front(of car) of manifolds together, T to exhaust is crimped, but manifolds are connected... I didn't put new gaskets between the tube and the manifold,

#4)EGR ?valves? on manifolds. These are vacuum diaphragms on the outer side of each manifold. they have a small nipple on them that connects to a T and then to right side of plastic air box.

#5) bad seal between carb and manifold? (on both sides?)

#6)bad seal between manifold and head? (both sides?)

Exhaust: sounds like the sound is on top of the engine, not on the bottom.

#7)exhaust output, exhaust leak. two ports on bottom of each head. pretty sure it isn't this. New gaskets between heater boxes and head... I glued them to the head with formagasket because they kept falling out while trying to bolt up the heater box.

Any ideas? I think the sound may be tied to the manifolds and EGR valves on the manifolds.

Jenny

Reply to
jboothbee
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What I find strange is that the chirping goes away when you pull the spark plugs.... Perhaps a slight head gasket leak? My 81 didn't even have them and it still ran though not well for long. only got 50,000 K out of that rebuild and I just did one and put them back on.

Reply to
westfaliaguy

I listened and it does have a "pneumatic" sound to it rather than a mechanical sound. What about cylinders-to-case? Does it change if you open the crankcase (oil filler)? I say cyls2case because I have heard from others that they produce a chirping sound although I have never had the problem on any of my own engines - I always coat the surface with gaskacinch or gorilla snot (weatherstrip adhesive) when assembling.

Whatever you discover, please be sure to post the "answer"! I can't imagine that if the valve lash was improperly adjusted that it would result in this sound - easy mistake to adjust them in the wrong sequence

- we have ALL done it!

If you pull all 4 plugs out, does it make the chirp? Pop a compression gauge in there while you have all 4 plugs out and just see where yer at.

I suspect that you can eliminate any vacuum side leak as it is quite well defined in its rise and fall - a vacuum type chirp would be more drawn out with a more gradual rise and fall - I think!

-BaH

Reply to
Busahaulic

I would guess that you have a warped rod, rings, or cylinder head. Sounds like the chirp is in 4/4 time.

Spray some Wd40 in the sprark plug holes and lube the heads. If the sound goes away, you have some head issues!

Could also be cam or crank , either is not good.

Reply to
Funkie

The chirp is indeed in 4/4 time. Interesting that it would alternate sides, unless both sides have the same problem. The fact that it goes away when you remove the plugs leads me to believe it's a compression leak, but from where? Normally, I would check things like this with a Cylinder leakdown tester (a.k.a. differential pressure tester) which fills the cylinder with air to check for burnt valves, etc. very common on air cooled Vee dubs) I'll assume you don't have one- To check for a cylinder to case leak, remove the oil fill cap. If you have a plugged crankcase breather, the sound should go away with the cap off. There should never be that much pressure inside the case anyway. If that doesn't solve it, on to the next issue. Heads: When was the last time the head bolts were re-torqued? I would pull the valve cover and check them with a torque wrench. If they're loose at all, you've probably found your leak- Try re-torquing the heads (good news, on a type 4 you may not have to pull the rockers if you have the right tools), and pray it goes away (if not they're warped or you may have burnt valves). In type 1 motors, loose heads produce a popping sound during moderate/heavy acceleration. Not to be confused with an exhaust leak which sounds similar but is constant. Does your bus do this?

Not to leave out the carburetors, make sure all hoses are connected properly and are not old and cracked, and the carbs are properly balanced.

Reply to
Dave G

thanks to everyone for replies:

1)heads are new 2)retorqued correctly 3)I did remove the barrels on both sides to put new spacers between barrels and case 4)I used formagasket between case and spacer, spacer and barrels 5)I remember this sound from before I replaced the heads. 6)hoses are connected properly

I think it could be the EGR valves on the intake manifolds...

I'll pull the manifolds, turn the engine over to see if the sound is still present, after I do the checks you suggested.

Thanks again,

Jenny

Reply to
jboothbee

Jenn I just did a 1700 that had that same sound it turned out to be the intake block was warped and wouldn't seal.

Reply to
Kafertoys

I pulled the carbs. Plugged the manifolds with rags so I don't drop anything in em.

Turn it over with starter. Still get the sound.

I pulled the manifolds.. plug the heads with rags... still get the sound...

but wait. I get visual that corresponds to the sound... cylinder 1 intake....rag is sucking into head when I hear sound cylinder 3 intake....rag is sucking into head when I hear sound

They seem to be sucking more air than the other cylinders, judging by how far the rags crunch in/out....

Hmmm. I followed procedure in VW manual to adjust valves. Time to look at it again.

The engine does run, and it runs good...

I cannot imagine valve problems on both sides of the engine, both on FRONT cylinder, both with same sound with new heads.

I'll let you guys know what happens with valve check and noise.

I definitely know it is in the heads now.

It looks like #1 and #3 are sucking more air. They are the cyl's making noises. I wonder:

does this mean #1 and #3 intake valves are too tight? Increasing velocity of air going past valve, causing whistle?

Jenny

Reply to
jboothbee

apparently not. I checked the valves and they are OK...

I need to find my compression tester and see if I have leaky cylinders/heads.

Jenny

Reply to
jboothbee

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