Advice/ help please, engine noise Options

[ILM914]

took my 74 914 out the other day on an errand, I have the orig Diet system on the car. all of the sudden while driving it sounded like an exhaust leak or flapping as the engine went. Also in between shifts and when I let off the gas the exhaust popped or had a small backfire. Small loss of power and a little rough running.

I'm going to do a compression or leak down on it but I wonder if any knowledgable folks know what this might be ?

If it's a head gasket what's the best way to change it and should i do all the head gaskets for all the cylinders ? thank you, Joe

[Root_Werks]

Would hope just a cracked exhaust pipe close the head.

A visual inspection from underneath might also help to tell if you have leak between cylinder and head.

Fingers crossed.

[Dlee6205]

Blown muffler? Loose spark plug?

[emerygt350]

Spark plug is a good suggestion.

[ILM914]

thanks guys checked the plugs and exhaust is solid also have that backfiring

[brant]

also if it happens to be an air injection motor... (I think they started in 1975, but sometimes a PO has changed a motor)

I've seen an air port pull out, or unscrews and gets lost.
big leak, and noticeable.

[SirAndy]

also if it happens to be an air injection motor... (I think they started in 1975, but sometimes a PO has changed a motor)

I've seen an air port pull out, or unscrews and gets lost.
big leak, and noticeable.

(IMG:style_emoticons/default/agree.gif)

[ILM914]

also if it happens to be an air injection motor... (I think they started in 1975, but sometimes a PO has changed a motor)

I've seen an air port pull out, or unscrews and gets lost.
big leak, and noticeable.

Thank you where is the Air Port ? Thanks

[brant]

Only on air injection motors

Mine are capped…. Thus the brass top on the air port

[brant]

And a close up

[ILM914]

thanks guys my motor doesn't have the air caps - has anyone done Head gadgets on the 2.0 ? what's the best way to do it ? thank you

[emerygt350]

Do they exist?

You need to start troubleshooting. Have you listened to it yet?

[wonkipop]

Do they exist?

You need to start troubleshooting. Have you listened to it yet?

right on @emerygt350

no head gaskets on a VW engine of any sort.
thermal expansion ultimately seals the motor.
a marvel of calculated differential expansion of different metals between crankcase,
jugs and heads.

why a little bit of warming up before driving off in a VW never does any harm.
but does a lot of good.

[L-Jet914]

Do they exist?

You need to start troubleshooting. Have you listened to it yet?

right on @emerygt350

no head gaskets on a VW engine of any sort.
thermal expansion ultimately seals the motor.
a marvel of calculated differential expansion of different metals between crankcase,
jugs and heads.

why a little bit of warming up before driving off in a VW never does any harm.
but does a lot of good.

The cylinder jugs did have sealing rings on the top and bottom of them. So in a way head gasket.

[wonkipop]

Do they exist?

You need to start troubleshooting. Have you listened to it yet?

right on @emerygt350

no head gaskets on a VW engine of any sort.
thermal expansion ultimately seals the motor.
a marvel of calculated differential expansion of different metals between crankcase,
jugs and heads.

why a little bit of warming up before driving off in a VW never does any harm.
but does a lot of good.

The cylinder jugs did have sealing rings on the top and bottom of them. So in a way head gasket.

sort of.
my understanding is the copper rings are there to stop the top of the jugs digging into the softer aluminium heads. but the real seal is done in the fit of the jugs to the heads (around the circumference). same at the block end. and its the thermal expansion that does the full tight fit when the engine is running. copper sealing rings set correct deck ht compression etc for factory standard engines.

i could be wrong. its what my old mechanic told me back when i had the squareback.
that they were not seals in the way we understand a trad head gasket.

but i suppose an overheated engine could distort its heads and get compression blow by out of the top or sides of the head.

in which case original poster with his engine sound troubles won't be fixing that with a "head gasket" job?

i think advice of other responders is correct.

i'd be looking at the exhaust outlet real close with the car up on a hoist and the engine running. advice to be methodical is very good advice.

[rhodyguy]

Push a block of 2x4 against the exhaust pipe. A leaky exhaust at a exhaust port and the noise will get louder. Well sealed on all 4? The engine should load up and stumble at idle.

[brant]

I’d guess exhaust also
Maybe a stripped stud?

Pull your HE for new copper ring seals and see what you find

[emerygt350]

With that loss of power it sounds like you lost a cylinder. Have you checked the plugs? The one that isn't firing (if it isn't) will look much different from the rest.

If it is a small loss of power, I don't think you would be losing a whole bank (and therefore probably not trigger points) and more likely a bad injector or bad spark to that cylinder. If I were you, I would (in this order):
1) do the 2x4 bit mentioned above to verify exhaust leak (good to know)
2) pull all the plugs looking for a wet/dark plug
3) while you have all the plugs out, do the compression check (again, good to know)

after that report back and we can go on to the next appropriate step.

[ILM914]

Thanks Guys i still haven't found the problem, I'm waiting for parts to make a leak down tester. Compression readings are as follows
#1 - 120
#2 - 110
#3 - 115
#4 - 120

[emerygt350]

Was that with all plugs out and throttle wide open? Did any plug look suspicious?