Super Beetle Engine Problems

volkswagen
beetle

#1

So I have this 1973 Super Beetle with a 1976 engine. After three months of horrible engine repair and electrical rewiring, I finally got the car in legal condition. However, on my way back from Austin the engine copped out. The first problem was the generator ball bearings broke. That was an easy fix. The second problem was the spark plug wires melted. Yeah, melted. So my engine wouldn’t start. And now, only one of the cylinders is flooded, so the car won’t start at all. Any idea where the hell I went wrong? I’ve tried to burn the gas out of the cylinder, and now the car makes popping noises as if it wants to start, but it seems like my timing is off. But I know the timing is right, and my firing order is right (1-4-3-2?) Any help will help


#2

OK, the generator’s bearings failed. Does that also mean that the generator, and therefor cooling fan, stopped turning? If so, I’m afraid that you may have just burned up your engine. That would also account for the melted sparkplug wires. That puppy got HOT.


#3

I tend to agree with MG here . . . do you know if you were running hot? You should have smelled it, noticed something. Does the engine turn over? How’s the oil look? Rocketman


#4

Oh yeah, it was running hot.

He said " The second problem was the spark plug wires melted."

That doesn’t happen in an engine running at normal temperatures. He cooked it. It’s toast.


#5

This being a Beetle, might he not have smelled it since the engine is behind the passenger compartment. (Not to mention all of the other smells that must be present in a 37yo bug…)


#6

the fan didn’t stop turning, it was just making a rough metal to metal sound. The engine wasn’t that hot, and didn’t smell. I was actually thinking that the wires melted due to an electrical problem. maybe too much juice being put out. is that possible?
and as for now, everything turns, and the engine cranks. It sounds really good, it just won’t start. It pops like there is combustion, but nothing happens.


#7

“I was actually thinking that the wires melted due to an electrical problem. maybe too much juice being put out. is that possible?”

No. The secondary ignition system can and will easily put out and withstand 40,000 volts. Yours was probably running at under 20K. That’s the norm.

If the fan was making metal to metal sounds when you observed it as you tried to start it, what’s to make you think it didn’t stop completely when it was TRYING to keep running. Just a loose belt could stop the generator and fan. A loose belt with a bad generator bearing is a shoe-in for stopping it.

Please do a compression test and get back to us. I still think you’ve cooked it.


#8

Run a compression test. Overheating severe enough to melt plug wires can also fry the engine.
Since no head gaskets are used, severe overheating can cause a poor cylinder to head fit and once they start leaking it’s time for some serious engine work.

Overheating could have been caused by improper installation of the fan nut and/or fan if this occurred after the generator bearing replacement. Another cause of overheating can be stuck thermostatic flaps in the fan housing.
Carelessness in removal and installation of the fan housing can cause the flaps to bind. (assuming the housing was removed for the generator (or alternator depending on the engine year)

A 73 is a carbureted engine and 76 should be injected so I’m curious if this is an F.I. conversion or an F.I. engine that has been converted to a carburetor.


#9

You wouldn’t happen to know what reading I should be getting when I do a compression test, would you?


#10

I read that it should be between 14 and 20, but that seems like a large range. Is that right?


#11

To provide a little perspective on the temperatures your engine was exposed to, spark plug wires are good to around 500 degrees F. If your ignition wires melted then you exceeded that temperature, you therefore have to assume the engines internal temperatures were far higher and may have exceeded the aluminium melting point of 1220 degrees F.

It’s therefore likely that you have burnt out valves or holed piston crowns, as the other posters advise, get a compression test before you start tearing it down.

But I’d say that engine is fried and may not even be rebuildable since those kind of temperatures will have altered the temper of some engine components.


#12

I did a compression test and there is no compression in any of my cylinders. What does that mean? I think (hope) it’s just that I ruined the piston rings, which wouldn’t be too difficult to fix. But is it very likely that I ruined the block?


#13

The air cools are prone to exhaust valve stem stretch anyway and combined with this severe overheating it’s likely that the valve lash has disappeared (tight valves). This means compression will be zero or very little.

This also means the cylinder heads will have to be rebuilt and proper rebuilding means they must be flycut also. Since overheating will cook the piston rings this also means the engine is toast because you do not want to perform a thorough top end job on this engine without going into the lower end also.

With the engine not running, grasp the crankshaft pulley and pull it towards you very firmly. Now shove it forward.
If you hear a clunk or light thunk sound this means the engine block is beaten out and simply verifies the engine must be totally overhauled.


#14

At a guess it means your exhaust valves are burnt out or you’ve melted the piston crowns. Either way with these temperatures you need to yank that engine for inspection, just pulling the heads will indicate the reason for no compression but there will be other unseen damage, at those temps the engine oil will have been compromised and crank / big end damage may well have occurred.

Only a thorough inspection will give you the full story.


#15

The inside of the cylinders could be inspected with a borescope stuck through the spark plug holes.


#16

ok so i took the engine apart and noticed that the pistons were slightly melted, so the rings weren’t sitting right, they weren’t opening and closing easily. So i filed down the pistons and put everything back together. Also, i noticed that my gas tank builds up a lot of pressure, and none of it is released from a valve, so it pushes more gas into the engine. This might have been where the flooding came from, and the overheating, because too much gas was being burned.
Is any of this plausible? I’m going to put the engine back in tomorrow, but if someone has an opinion otherwise I’d like to hear it so i didn’t have to take the engine out again.


#17

No one and I mean no one re-uses VW piston and cylinders. After an overheat event they are throw away items. I suggest you find a way to stow a bicycle in the back of you Super Beetle.


#18

Hmm,
Slightly melted. Did you expect a pool of metal? The cylinders, pistons, heads, valves, and likely the crank is toast. Done kaput finito. Did you spec the parts with a micrometer or just kinda look at them? The pistons in this car cannot be filed down except at the piston skirt and only to balance the weight to the other pistons. Do not run this engine you are in way over your head.


#19

Spar, don’t let some of the comment(s) here get to you. They are right, however. Your engine is history. I don’t know about the rest of the car. You could possibly install a used engine, but I just have the feeling that whole car is a complete liability.

Maybe you should save your pennies and get a cheap used car somewhere.

Good luck to you.


#20

I think you’re in trouble here and comments are correct about the reuse of cylinders and pistons. Reuse is a pretty iffy deal even when done by someone who is very familiar with air cools and their quirks.

It’s not likely this overheating was caused by any fuel problem. Based on the melted piston comment I would say this was caused by one of three things.

  1. Ignition timing advanced too far.
  2. Leaking intake boots.
  3. Poor cylinder to head fit leading to air being sucked between the cylinder and head junction. (this is kind of my first choice here)

Even when new cylinders and heads are used they should be hand mated together for a perfect fit by using Prussian Blue and valve lapping compound. When it comes to used ones (always a gamble) this usually means having the heads flycut and doing the same thing.

You’re likely going to pull this motor again and should definitely not get too far from the house with it.