NOT-Cracked piston in Corrado!

Started by Rossi, October 20, 2006, 05:38:04 PM

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Rossi

This ones a major...

I recently had a problem with losing coolant, there was some seepage arond the hose clamps so I thought it was just that.  But after replacing some hoses and clamps I was still losing coolant and now everything in the engine bay was dry, i.e. no leaks.  Therefore I started to think it must be a head gasket problem and that the coolant was going through to the combustion chamber.  This theory was reinforced by the car sometimes running on three briefly after start, although the compressions were all good.

Last weekend i pulled the head off (this went well and was remakably easy) and found lots of evidence that it had been leaking coolant into no. 4.  The gasket showed signs of leakage and the piston crown, valves and exhaust manifold were all much cleaner than the others.

Unfortunately when i cleaned the crown of the no.4 piston I discovered a pair of cracks in it. :o Presumeably they were caused by the strain created by turning the engine over with incompressable coolant in the combustion chamber.  Strangely all the pistons seem to have a hand scribed line about 20mm long scratched into the flat surface of the crown, on the number 4 the main crack is roughly perpendicular to and through the middle of the scratched line and a smaller crack has propegated off one end of the line. In the attached photo you can see the scribed line running close to horizontal and the two cracks running vertically.
2001 S4 Avant.
Corrado 16v - BR Motorsport ported KR 1.8l head with 284deg schrick cams, 9A 2.0l block, Milltek headers, K&N filter, 40mm lowered on PI springs/Boge shocks + VR6 strut mounts, front poly bushes, 280mm G60 front discs, 16" Porsche replica mags.

Rossi

So obviously thats going to need to be fixed...

I assume the damaged piston cant be viably repaired so I will need to replace it at the minimum, if not all four.  Plus rings i guess, plus conrod bearings while I'm there, etc etc etc...

Does anyone have any 9A (2.0l 16v) pistons, or a whole bottom end sitting around?

This weekend I will either try and pull the sump and and remove the piston(s) from the top, or just pull the whole engine. Any reccommendations on this?

I will probably order a load of parts from www.autohausaz.com , they seem to be cheaper and have a better range than www.parts4vw.com.  I may yet look at a set of new forged psitons as well, possibly high compression. >:D

Looks like I'm going to have dirty finger nails for a long time.
2001 S4 Avant.
Corrado 16v - BR Motorsport ported KR 1.8l head with 284deg schrick cams, 9A 2.0l block, Milltek headers, K&N filter, 40mm lowered on PI springs/Boge shocks + VR6 strut mounts, front poly bushes, 280mm G60 front discs, 16" Porsche replica mags.

typ53

Bugger.  It's never a simple is it?

Talk to Neil: He's just been through the exercise of pricing almost exactly what you are suggesting.
The Fleet:
Orange Roughy:'90 16v Corrado
'89 Carrera 4. 
'12 330d Touring
Still trying to figure out how to get 'em all to fit in a single garage....

robh

thats bad news, sorry to hear your bad luck.  have you tried Nigel at vwspares?  I know they did have a complete 9A 16v for sale, not sure if they still have it.  The other option is I could try getting a 9A from those wreckers in Auckland where you have to pull it yourself (can't remember name?) they had at least 3 passat's with 9A's that you could maybe use and would be cheaper than vwspares, but you wouldn't know if they ran or not.  Nigel always runs his engines before pulling them.

let us know if you want us to go looking for you up here...
Daily Driver - VW Touareg V8 TDI 2012 "towing beast"
Too Many Cars - Lotus Elise S 2013 "tangerine dream"
Project Car - Golf VR6 Turbo "built not bought"
Wifes - Audi S4 Avant 2012 "I want a white car that sounds nice"

qta4

Reflections on my experience with projects like you are facing,

Remove engine ,strip clean thoroughly check every component,measure every component, replace every suspect part.

Approaching this project any other way will always allow surprises to surface later and cost lots more.

The only way you will sleep is to know every part is 100%.

Especially if you wish to keep car and upgrade performance in future

I took the other approach last century ,,,,,,, never again.

Skill is, sucessfully tightrope walking across the Niagra Falls.
Intelligence is, having the sense not to do it.

rambo_005

Can hopefully help mate, have just sent you a PM.

orggti

After seeing the pics, im tempted to say the cracks have been there since that was put together. They scrachged them to created a stress point going the other way and then did it to all of them incase there were unseen crack on the others. Im just inventing this in my head so ...................Old mechanics have many tricks and many engines have been put toghter with what people have, no money to spend.

I, would refit a head gasket and not worry about that crack, it may have been there for ages. Your block is nothing special so if it pops who cares. then whilst you have a car to drive get a nice new block built up in good enjoyable time ;) I right eh? Or do you guys think it wont last a minuit?
Hope i got to this in time? youve probly got it in bits now eh?

Rossi

Looks like the joke and the drinks are both on me!

Thanks to the VASK member who built this engine all is revealed...
What looks like a scratch and two cracks is in fact three scratches which, you guessed it, form the number four!

Don't I feel like a right twat!  Still at least I hadn't rushed into pulling the block or ordering $1000 worth of JE pistons! 

Its funny how the light made the "cracks" look completely different to the "scratch", and the way they were squiggley looked just like a crack, but there you go...
Now I just need a head gasket and I'll be back on the road.
Thanks everyone for your help and sorry for the false alarm.
2001 S4 Avant.
Corrado 16v - BR Motorsport ported KR 1.8l head with 284deg schrick cams, 9A 2.0l block, Milltek headers, K&N filter, 40mm lowered on PI springs/Boge shocks + VR6 strut mounts, front poly bushes, 280mm G60 front discs, 16" Porsche replica mags.

orggti

I still enjoyed my stress relief theory  :laugh: Good news rossi and my advice was the best as if you had just bung it together it would have been sweet ;)

johnp

Quote from: Rossi on October 22, 2006, 03:10:45 PM
Looks like the joke and the drinks are both on me!

Thanks to the VASK member who built this engine all is revealed...
What looks like a scratch and two cracks is in fact three scratches which, you guessed it, form the number four!

Don't I feel like a right twat!  Still at least I hadn't rushed into pulling the block or ordering $1000 worth of JE pistons! 

Its funny how the light made the "cracks" look completely different to the "scratch", and the way they were squiggley looked just like a crack, but there you go...
Now I just need a head gasket and I'll be back on the road.
Thanks everyone for your help and sorry for the false alarm.

Hi, you should get the head checked for straightness thru the cam tunnels as well as the gasket surface to make sure it is not bent.
Also make sure the head alloy is not "soft", which can happen with prolonged high temperature running.
This is what happened to mine, bent and soft.  (the cylider head i mean!!)
Replacement of the headbolts is also a MUST.

orggti

A MUST :o Those are strong words your useing  :D HOw much do they cost? and do you mean a "must" for 16v only or 8 valves too?
I did Nastnas mums rover K series engine after it mixed its oil and water real badly. Whole block was alloy and the bolts went all the way through the alloy block and into the bottom of the engine and it said in the book to replace all the bolts. Now Rover wanted $180 for a top radiator water hose and even then had to order one in, so i didnt even ask how much a set of head bolts were gona cost, anyway i got the head refaced, head gasket only, from partmaster and got a spacer made up to fix the origional top hose for $25 bucks and the new side tank on the rad which was what caused it all to happen in the first place. It still going great nearly a year and a half later at least now.
An to be honest i dint know if it would make it round the block it was such a cantankerus piece of tiny little castings that cant handle heatand dislodgeable bores and threadable alloy threads. Worked tho, Nastys Mum was so happy. So was I :)   

robh

ARP headbolts for a 16v are only $125 US from Schimmel Performance and they are reuseable unlike the factory ones.
Daily Driver - VW Touareg V8 TDI 2012 "towing beast"
Too Many Cars - Lotus Elise S 2013 "tangerine dream"
Project Car - Golf VR6 Turbo "built not bought"
Wifes - Audi S4 Avant 2012 "I want a white car that sounds nice"

vwrally

OEM head bolts work by stretching when you torque them up and hence should always be replaced, oem are about 120

or I use the the studs which VWR use, like ARP they are reusable and havine a higher holding pressure.

Cheap insurance vs a reused bolt breaking or pulling a thread

The same applies to rod and bottom end bolts

orggti

Do you have to replace 8v headbolts too? As I say I never have and havent had any problems with any head gasket ive ever done and thats quite a few now.

vwrally

Thats what they say

I have reused them on some motors but never on anything that I have spent money on and that I know will get the odd thrashing

Rossi

Woohoo!  I'm back on the road!

And don't worry, I used new head bolts!  I got all my parts from www.autohausaz.com, cost me $250 NZD landed and only took a week.  This inculded head gasket, head bolts, intake and exhaust gaskets, cam chain, cam belt tensioner, oil filter, fuel injector o rings....All .good branded german stuff too.  Excellent value, highly reccomneded.

While i had the head off I discovered "BR Motorsports #9020" engraved on it from when it was originally tuned in the UK.  Its been beatifully ported by them;D
2001 S4 Avant.
Corrado 16v - BR Motorsport ported KR 1.8l head with 284deg schrick cams, 9A 2.0l block, Milltek headers, K&N filter, 40mm lowered on PI springs/Boge shocks + VR6 strut mounts, front poly bushes, 280mm G60 front discs, 16" Porsche replica mags.

orggti

Excellent news Rossi :) Thats sounds like an awsum deal on the parts, we must all be crazy to buy anywhere else it would seem.

robh

that's awesome news, great that it didn't cost thousands to get going again.
Daily Driver - VW Touareg V8 TDI 2012 "towing beast"
Too Many Cars - Lotus Elise S 2013 "tangerine dream"
Project Car - Golf VR6 Turbo "built not bought"
Wifes - Audi S4 Avant 2012 "I want a white car that sounds nice"

johnp

Quote from: johnp on October 25, 2006, 03:52:13 PM
Hi, you should get the head checked for straightness thru the cam tunnels as well as the gasket surface to make sure it is not bent.
Also make sure the head alloy is not "soft", which can happen with prolonged high temperature running.
This is what happened to mine, bent and soft.  (the cylider head i mean!!)
Replacement of the headbolts is also a MUST.
sorry did not see this until now......
Yes, it is a MUST to replace 16V headbolts, when first used they are torqued to their elastic stage. When you reuse them they will torque past the elastic stage as this has already been done. The clamping load will NOT be correct.
Engineers with many years of theoretical and practical experience have worked this out, it is fact not opinion.
You CAN reuse 8V headbolts, but most good shops will not as you can never be sure if the head has been off and bolts reused before. It is cheap insurance.
A set of 16V bolts would be around $80.00 trade, 8V cheaper. (elring were the last set I used)


orggti

You sayijng that the 8v ones can be reused only once? Where do you buy the bolts? qualitat?