The "what I did to my Corrado today" thread...

[Jim Bowen 1]

It just started making a loud noise, at first i thought it was the engine noise from the V8 merc behind me, but then realised it was mine (whenever i got to about 4000rpm), Then it just dropped power and made a bit of a bang, i thought i could hear bits of metal hitting the road but i'm started to think it was a valve going down the exhaust pipe.

 

I'll fix it, not sure what route to take until i see whats wrong, would be interesting to know what and why this has happened. At the moment i'm blaming the head i bought (was about the only part i could have doubts about)

[Jim 1]

That's horrendous :(

[Dox 22]

The head off a valve is too large to go down an exhaust port, inlet vValve is larger still

[Jim Bowen 1]

Might just be a bit of a valve, i've had about a 1/3 of a valve break off before on a previous car.

[Dox 22]

Can you pick the particles up with a magnet?

[Jim Bowen 1]

No they seem to be alloy.

 

Got as far as this tonight. Head studs are all loosened off. Will lift head off tomorrow

 

[Jim Bowen 1]

Now I'm confused. Got the head off and can't see anything wrong. All valves look ok and so do the tops of pistons.

 

Will turn it over on the crank pulley so i can see all the bores. But all look ok.

 

What are the symptoms of something wrong with the crank? Can't for the life of me think what the noise of things falling off were?

[Dox 22]

Now I'm confused. Got the head off and can't see anything wrong. All valves look ok and so do the tops of pistons.

 

Will turn it over on the crank pulley so i can see all the bores. But all look ok.

 

What are the symptoms of something wrong with the crank? Can't for the life of me think what the noise of things falling off were?

 

Grab the crank pulley and push / pull, there should be hardly any movement.

 

You say the debris is non ferrous?? The block is cast iron, so bottom end wise its just pistons, oil pump and bearing shells that are a possibility?

 

The head is alloy so just about anything is a possibility.

[Jim Bowen 1]

Yeah i have a magnetic sump plug, was metal on that, not lots but more than last oil change, was some of it when running in and doing the first oil change.

And the stuff left in sump wasn't picking up with the magnet.

 

Will try the crank tomorrow, cheers.

[Jim Bowen 1]

Slept on it (not the corrado), but thinking about what happened and i'm none the wiser.

 

Something definitely broke, very rough sounding engine and ran lumpy, and the sound like something fell off the car or has been flung around inside the engine or bay.

 

Couple of questions.

DO i need the head skimmed again, now that i've removed it?

Will probably fit a new headgasket if i put this engine back together, whats the metal one people recommend?

[GlosterOx 0]

The metal one Jim is the MK4 Golf version, raises the compression ratio up to about 10.5/1 for a few extra BHP - I have it fitted to mine.

 

Ian.

[Dox 22]

Slept on it (not the corrado), but thinking about what happened and i'm none the wiser.

 

Something definitely broke, very rough sounding engine and ran lumpy, and the sound like something fell off the car or has been flung around inside the engine or bay.

 

Couple of questions.

DO i need the head skimmed again, now that i've removed it?

Will probably fit a new headgasket if i put this engine back together, whats the metal one people recommend?

 

You can't reuse head gaskets as they compress to make a seal.

 

MLS (multi layer steel) are the ones that raise compression a tad.

 

The head shouldn't need a skim unless its been overheated? Place a straight edge rule across the head face diagonally in both directions to see if the head is true - you'll need 3 spacers (identical M6 or M8 nuts?) to clear the valves as they're proud of the surface.

 

Valves are made of 2 pieces of metal, the head is of a hard material, the stem is much softer, they're friction welded together by spinning them under pressure, its usually the head that comes off complete at the welded point (after serious overheating) holing the softer piston, if you drove the car with a holed piston the exhaust would have oil dripping out of it and all over the rear of the car.

 

I think you need to find out what the debris is, alloy from a casting or white metal (very soft - made with lead and tin mixture)) from the big ends or mains. If its bearing material then you need to look at oil supply, the crank actually floats on oil and shouldn't touch the bearings at all, if oil supply is an issue the white metal is destroyed very quickly if the crank journals touch the surface of the bearings. there's thrust washers too (also white metal), these control sideways movement of the crank - hence why I said push / pull on the crank pulley to check for play.

[Jim Bowen 1]

Bottom end was a new unit, i took that to stealth with new pistons/rings and asked them to use my old crank and rods, and told them anything else that needs renewing they can buy in the best quality they would use and fit them.

 

Thanks for all the info, very helpful, i still feel i'm learning as i go.

 

Its starting to look like i might need to talk to stealth about the bottom end.

[Jim Bowen 1]

Spoke with Vince, he thinks it sounds like a bearing shell from oil starvation. Maybe it was my oil pump making the noise which i thought was the PAS pump. Strange as that was a new unit from VW. I think i'll be taking engine out and taking the whole lot to stealth.

[Jim 1]

I was going to say, I wondered if it was a bearing shell. On the plus side, if that's all it is, then it's not the end of the world :)

[fla 9]

Glad Vince thinks what i thought as well re the bearing shells!

Certainly seems to be in good order as you describe - bear in mind sound travels very quickly in metal so whilst it sounded terminal it looks like the issue may be easily rectified. Fingers crossed for you Jim - keen to see Vince's verdict afterwards.

[Dox 22]

Spoke with Vince, he thinks it sounds like a bearing shell from oil starvation. Maybe it was my oil pump making the noise which i thought was the PAS pump. Strange as that was a new unit from VW. I think i'll be taking engine out and taking the whole lot to stealth.

 

I remember your rebuild well, the best of everything so its a bitter pill when things like this happen. You'll need to strip and clean the head to remove the debris from inside the oil galleries / passageways too.

[Dox 22]

If enough white metal is ground away from the shells the outer steel part of the shell can spin around and make a horrible noise (I was at Curborough when Pete Rosenthals MK1 Golf spun its bearings on the main straight - Pete was VW motorings staff writer at the time, the noise was horrific but he never heard a thing).

 

The bearing shells are steel outer, coated with copper, then coated with white metal then machined round, the sign of a worn bearing is the copper coloured coating showing when removed - the white metal is gone.

[Jim Bowen 1]

Yeah, i did spend quite a bit of money on it (and time)

 

Is a bearing shell an easy fix? More worrying me is why its been starved of oil. Might stop investigating and just fit the other engine for now and let stealth sort this engine out.

[Jim Bowen 1]

If enough white metal is ground away from the shells the outer steel part of the shell can spin around and make a horrible noise (I was at Curborough when Pete Rosenthals MK1 Golf spun its bearings on the main straight - Pete was VW motorings staff writer at the time, the noise was horrific but he never heard a thing).

 

The bearing shells are steel outer, coated with copper, then coated with white metal then machined round, the sign of a worn bearing is the copper coloured coating showing when removed - the white metal is gone.

 

This makes a lot of sense, some of what is in the sump looks coppery coloured.

[Dox 22]

 

They should be lead coloured

Edited April 15, 2016 by Dox
crap link replaced with a pic

[Jim Bowen 1]

Would people normally replace all of them? Also is there two half circles (shells) for each con rod? Like a top and bottom?

[Thursdave 10]

Spoke with Vince, he thinks it sounds like a bearing shell from oil starvation. Maybe it was my oil pump making the noise which i thought was the PAS pump. Strange as that was a new unit from VW. I think i'll be taking engine out and taking the whole lot to stealth.

 

How new was it?

 

all VW parts have a 2 year guarantee against manufacturing defect. If it turns out it is the new oil pump that's caused this you should be able to claim for a new one, and for all the repair work under that warranty as consequential damages.

[Dox 22]

Would people normally replace all of them? Also is there two half circles (shells) for each con rod? Like a top and bottom?

 

The bearings are usually only sold in sets, main bearing that the crank sits inside the block and big ends that the con rods connect to the crank are both in 2 halves, so a 6 cylinder car has 12 big end bearing shells, if the engine block has 7 bearing saddles then its 14 main bearing shells

[Jim Bowen 1]

How new was it?

 

all VW parts have a 2 year guarantee against manufacturing defect. If it turns out it is the new oil pump that's caused this you should be able to claim for a new one, and for all the repair work under that warranty as consequential damages.

 

Will be 2yrs in september i think, thats when i picked the bottom end up from Stealth and they bought the pump for me. Interesting to know about the warranty.