Valve problem, This time I think I'm screwed Options

[fitzm1]

Just finished all the work I had planned for this spring. Bump steer kit, CB fuel pump and cleaned (rebuilt ) the carb that has been giving me problems. Seemed to be running great. As I am going up a hill near home I hear a pop and the engine sounds like a sewing machine. First I thought I had lost a gear in the tranny but that seems fine. I checked the compression and all cylinders are 120. Car starts fine but sounds like one or more of the valves are real loud. Any explanation besides the one I fear (trashed motor).
Joe I think I broke your motor.
Mike

[underthetire]

Mine did the same thing yesterday. Ended up a head pipe came loose.

[Elliot Cannon]

Collapsed lifter??? (IMG:style_emoticons/default/confused24.gif)

[Scott S]

What motor are you running? I had something very similar happen on my 2.0 right after the rebuild. It was a late motor (air pump) and I had one of the plugs from the air injector ports come loose. Scared me to death. A little lock tight and a wrench and I have been fine for 13 years....

[Cupomeat]

Ok, so if all the cylinders have even compression then you can generally rule out alot of bad things;
1. You did not eat a valve
2. You did not put a hole in the piston

Now, have you pulled the valve covers and watched the rocker arms go as you rotate the motor. If you fear it to be valve train, do this first and see what happens.

Perhaps a pop is the rocker arm set coming loose, or a push rod properly seating in the rocker?

You'll have to dive a little for this one, but perhaps not too deep before you know.

Pull them valve covers and see what you find.

BTW, was the "pop" a backfire style, or a mechanical pop?

sir, for the record, would you describe the "pop"... LOL

[fitzm1]

Pulling the valve covers and checking the valves is on for tomorrow. It sounds like a tapping. I have a stethoscope and have listened to the valves with it before. Now it sounds much louder than before and louder near no.3 cylinder. The pop was a mechanical type noise and the car lost power like I lost a cylinder, but it doesn't idle rough like its firing on three, it just makes a lot of noise.

Ok, so if all the cylinders have even compression then you can generally rule out alot of bad things;
1. You did not eat a valve
2. You did not put a hole in the piston

Now, have you pulled the valve covers and watched the rocker arms go as you rotate the motor. If you fear it to be valve train, do this first and see what happens.

Perhaps a pop is the rocker arm set coming loose, or a push rod properly seating in the rocker?

You'll have to dive a little for this one, but perhaps not too deep before you know.

Pull them valve covers and see what you find.

BTW, was the "pop" a backfire style, or a mechanical pop?

sir, for the record, would you describe the "pop"... LOL

[SGB]

plugs in tight?

if an exhaust stud pulled out, the exhaust leaks under the engine- but what you hear is the exhaust valve going clan-clang-clang.

almost every valve concern I've had turned out to be pulled exhaust studs- which are a pretty cheap repair at an ol school VW shop

[fitzm1]

Plugs were in tight. I just checked the valve clearances and they were spot on. I hope this means I can't have a collapsed pushrod. I checked the exhaust studs they all seem to be tight. Tommrow I'll slap it back together an start it up again. I'm missing something here. That Newbie by my avatar is well deserved.

plugs in tight?

if an exhaust stud pulled out, the exhaust leaks under the engine- but what you hear is the exhaust valve going clan-clang-clang.

almost every valve concern I've had turned out to be pulled exhaust studs- which are a pretty cheap repair at an ol school VW shop

[Katmanken]

Coupla options.

Check the exhaust studs to see if one pulled out.

Remove the rocker shafts and pull and check the pushrods for straightness. Make sure they fit back into the cam followers when re-assembling

Or, lay under the car with the valve covers off with the engine in gear and one wheel up in the air. Spim the wheel in the air to rotate the engine and watch the rockers move the valves open and closed. Look for one with a difference.

[r_towle]

Take the valve covers off, jack up the passenger side of the car so that wheel is off the ground and the drivers side rear wheel is on the ground.

Put the car in 5th gear.
While laying on the ground and watching the rockers, turn the passenger wheel backwards...as if you were in reverse.
This turns the motor forwards.

You have have a broken spring, or you may have not seated a push rod correctly and once it finally did seat, that valve no longer opens (thus you loose power)

Or, you dropped a valve seat.
Either way. stop running the motor..just turn it by hand until you figure it out.
You should be able to turn the motor through all four compression strokes by hand and not feel and resistance.

RIch

[euro911]

... Either way. stop running the motor..just turn it by hand until you figure it out.
You should be able to turn the motor through all four compression strokes by hand and not feel and resistance.

RIch

(IMG:style_emoticons/default/idea.gif) ... and remember ... it's a whole lot easier to rotate through all 4 cycles if you remove the spark plugs (IMG:style_emoticons/default/w00t.gif)

[fitzm1]

I have the car up on stands. I have checked the valve clearances using Cap'n Krusty's valve adjustment technique. I have .008Ex & .006In. I don't see how I could have a pushrod problem.

I'll do another compression check.

Is it possible that a valve could drop but snap back into place to give good compression readings? That would explain why it goes through all the cycles via the wheel turning. Could I be hearing a valve seat not quite out but slapping in and out a few mils? That could also be the reason the car kept running.
Possible?

Take the valve covers off, jack up the passenger side of the car so that wheel is off the ground and the drivers side rear wheel is on the ground.

Put the car in 5th gear.
While laying on the ground and watching the rockers, turn the passenger wheel backwards...as if you were in reverse.
This turns the motor forwards.

You have have a broken spring, or you may have not seated a push rod correctly and once it finally did seat, that valve no longer opens (thus you loose power)

Or, you dropped a valve seat.
Either way. stop running the motor..just turn it by hand until you figure it out.
You should be able to turn the motor through all four compression strokes by hand and not feel and resistance.

RIch

[Dave_Darling]

When one of my valve seats did that, it was deformed enough that I had essentially zero compression on that cylinder.

I'm still thinking it's an exhaust leak or something similar, not an internal engine problem.

--DD

[Bartlett 914]

Is it possible that a valve could drop but snap back into place to give good compression readings? That would explain why it goes through all the cycles via the wheel turning. Could I be hearing a valve seat not quite out but slapping in and out a few mils? That could also be the reason the car kept running.
Possible?

Yes it can. I had this happen on a 2.0. I was so surprised to see how loose the seat was when I took the head off. My car ran for a long time this way until finally I lost compression all together on that cylinder.

[fitzm1]

Is it possible that a valve could drop but snap back into place to give good compression readings? That would explain why it goes through all the cycles via the wheel turning. Could I be hearing a valve seat not quite out but slapping in and out a few mils? That could also be the reason the car kept running.
Possible?

Yes it can. I had this happen on a 2.0. I was so surprised to see how loose the seat was when I took the head off. My car ran for a long time this way until finally I lost compression all together on that cylinder.

Seems to be coming from cylinder no. 3 (naturally). Can the 3,4 head be removed in the car (after the HE is removed)?

[fitzm1]

When one of my valve seats did that, it was deformed enough that I had essentially zero compression on that cylinder.

I'm still thinking it's an exhaust leak or something similar, not an internal engine problem.

--DD

Pulled the HEs today (This could get addictive). It looks like theres blow by on 1,3,4

[fitzm1]

When one of my valve seats did that, it was deformed enough that I had essentially zero compression on that cylinder.

I'm still thinking it's an exhaust leak or something similar, not an internal engine problem.

--DD

Pulled the HEs today (This could get addictive). It looks like theres blow by on 1,3,4. The studs seemed to be tight but the copper gaskets are black. Could this amount of leakage cause the valve lash to sound so loud?

[euro911]

I helped a guy remove a leaking exhaust to find the old copper gaskets still seated in the exhaust ports ... in addition to another set someone installed (IMG:style_emoticons/default/blink.gif)

They were hard to see because they were black and jammed in there pretty tight - took a bit of time, patience and special tools to get them out (IMG:style_emoticons/default/chowtime.gif)

... don't know if this applies to your situation or not (IMG:style_emoticons/default/confused24.gif)