piston condition 83 dx gti

Hi all,

As the head has just been renewed and hopefully going back on soon, the workshop reckons the bottom end looks fine.
After the previous owner said he rebuilt the bottom end in 1999 and the car has only done say 200 miles since I am hoping that it is ok.
Crank has been inspected and the workshop sees no issues, so looks like he was telling the truth. The bores measure at about 81.5mm

However, with the original Head having been skimmed by 1mm there was obviously a lot of compression which probably caused the overheating too.



Can anyone tell of the piston heads themselves look ok?
Has the increased compression ruined the piston(s) nearest the gearbox?

I've learned a bit about the cylinder heads since getting it tidied up but would appreciate some help on the state of the bottom & pistons please.


Thanks,

Si

1mm shouldn't cause overheating.


A plugged radiator matrix, and or iffy t-stat, water pump are the more likely aspects.  
Once you get the head re-installed then flushing and back flushing the coolant system is a better things to do, as the car is apart, you could run your radiator to a shop and have it boiled out and tested.

Also if your car has a non-a/c radiator, then upping for a a/c radiator is a good thing as well as it larger than the non-a/c radiator.

If you have the water jacketed oil cooler installed you may want to replace that with an external oil cooler as it is one less thing that you have to worry about for oil/water issues, as well as a being plugged, and not cooling anything,  If it is still the original, I would replace it out of hand as you are doing allthis other work.  (they get plugged too)

Hi, Does number 4 Piston have a hole in it ?

Thanks for the posts guys.

Brian, the car uses the original oil cooler. Same one VW brought over from the beetle. I recently came to think that unless you are using the car for track days, you would not need an aftermarket oil cooler.

In any case, is this the type you are talking about…?

https://www.vwheritage.com/wc1179299-oil-cooler-kit-24-row-with-sandwich-plate-type-4-engine-m

I am not sure which radiator has. It is definitely Hella but I read somewhere the GTi ones are different. How can I check I have the correct one?
Do you have a link for the a/c radiator please?


Greavsy, I cannot answer that pal.

I am going to look at the car tomorrow though so will hopefully be able to give an answer after. The workshop definitely have not mentioned anything like a damaged piston though.
Will see if we can get the pistons pushed up… can this be done with the sump still on?

Spoke to a few folks today about the bores. I will have a feel if they are scored, as well as checking if piston 3 and especially 4 have excess carbon. David Knight (Knight engines) reckons there may be scratches to the bore of cyl. 3 as you can speckles/stars. I'm hoping this is just a distorted reflection of the piston from the camera flash.

I am a little concerned about the horizontal u-shape [__] on walls of cyl. 2 & 3 though. If you can see what I am referring to, could this be early signs of piston slap?

More pics to follow tomorrow hopefully.

Thanks

  Ok mate, no problem. It may just be a build up of carbon on the piston.  What mileage has the Engine done ?
 

It's done 110k Greavsy. It's been around that mark since I got the car in '06. Previous owner only did a couple hundred miles after rebuilding it in '99.

I was meaning to add also, the car was running absolutely fine after it's MOT this August. That was the first time in 10 years it had been driven. Back when I got it, it was always idling high and running rich. Might explain the carbon build-up too.

When the workshop inspected the crank, there was no scare of bits of metal/engine sitting in the sump.

That does just look like carbon build up from running to rich, short journeys and driven around town like a Nun going to Church, the exhaust manifold also looks black inside.
Just starting up the engine and warming it up every now and then and not driving it is not good for the engine, get the mixture right 2%CO is what you are looking for and check the timing is good and the car is running on super unleaded and then  you need to get it out on the road and give it a dam good thrashing, get things nice and hot, then it may blow all the cr*p out of the exhaust.
Only do this once things are run in again after the engine has been put back together, you can clean all the carbon of the tops of the Pistons which will help.

  Ok mate. If it was running well the piston can't be holed. And at a 110,000 miles it's still "young"  lol. Mines done a similar mileage at about 112,000. Good luck with it. 

Mark, top man! Thanks for the advice.

As long as the findings tomorrow give the all clear on the bores, i'll have everything tidied up before the top end goes back on, with new gaskets too. The mani' might be a bit trickier though!


Greavsy, thanks again pal.

I agree it is relatively young but might have been better off with some proper mileage under the belt over the last 17 years.    
Almost half life sitting!  

Pics to follow tomorrow hopefully.

  Morning.. As Mark says ,when it's all back together it needs a proper run out to clear all the carbon build up. However, once the garage have done their stuff it should be reasonably clean.   Ours had been stood for 10 years when my Son bought it as a non runner a couple of years ago.  We got it running then did some work on it to get it Mot'd and it was then used daily.  He's now emigrated so I bought it from him and it gets used regularly but not daily.

  Don't forget, back in the day a "De coke" was done to a car every year to clean out the carbon/ soot. Advances in fuel technology put an end to that. Kev.

Hi Kev,

Not sure what your symptoms were for having a non-runner but i've experienced various teething issues. So replaced fuel lines, pressure sensors, coolant hoses etc. Glad to hear it is being ran regularly… keeps them happy :-)

Managed to have a look at the bores today and fortunately everything looks fine. I thought the swirls were score marks but realised they were too consistent and obviously honing marks.

Had a feel of the cylinder bores and you can't notice the honing marks, everything is nice and smooth on bores 1 & 4 (exposed ones)



cylinder 1 ^



cylinder 4 ^



cylinder 4 again ^

There were consistent carbon marks at the tops of the bores… about 4mm but this can be cleaned up. The bores have not stepped at the top or anything. Phew.



cylinder 1 again ^

The mysterious [__] on the cylinder walls was just reflection, so too were the shiny stars I thought I was seeing.  I recall the head being in such a state that it was not 100% level and this maybe explains the extra carbon on pistons 3 & 4 perhaps. Fortunately it will be given a good tidy up before the head goes on. As the new head has not been over skimmed i'll going for a composite gasket rather than MLS.


Si

Hi there.. Good news then !!  Non starting issue for us was a seized Fuel Pump, the one under the car. Once replaced she fired up first turn of the key !

Ha! Snap!

Maybe our cars are twins  

Lol   What a coincidence !