Engine number 3 now

[Highside43]

What causes a hole in a piston please?

Less than 500 miles driving of collecting my car at Easter weekend (after being 10 months in a garage having a refreshed VVC engine fitted - forged con rods, forged pistons, new triple pass rad from Caterham, Emerald ECU, Piper Cams (mild ones) and blanking kit and a whole raft of new bits as well as skimming the head and new liners), it has gone back due to the radiator spewing it's contents all over the place in the second weekend of driving it - enough for me to have to call the AA out - and the temp suddenly shooting into the red.  After shelling out out many thousands of pounds fixing the knackered engine the car had when I bought it (20 months ago, and it's been in a garage for 11 of those....), it now apparently has a hole in one piston, and the radiator is leaking all over the place from everywhere (no stone damage, it's coming from the welds).

Would a hot engine cause the piston to form a hole in the top?  I'm no mechanic but understand the basics from tinkering with bike engines 20 odd years ago. Garage is saying it's because of the radiator failing and the engine getting hot.  Who do I throw this several thousand pound bill at now for fixing my newly ruined engine, as I don't see why I should have to pay again.

I'm not happy.

[revilla]

I'd be surprised if a rad failure caused a holed piston. Sounds more like running very lean.

[philwaters]

I agree, more likely to be have been running lean - have you had it on a RR since fitting the cams?

[ChrisC]

Years ago, when I had a habit of fitting turbos to (proper) minis I holed a piston driving to the rolling road.   The fuel return line was under sized at the first attempt which meant the fuel pressure was to high, causing over fueling everywhere, once that was sorted the drive to the rolling road killed a piston because it ran lean :-(.    It also melted the plugs.    

[CycleSi]

I'd agree too on the piston issue - too lean.

Regarding the rad - that happened to mine recently and we think it was down to vibration causing the welds to fail. 

A poorly constructed rad and/or poor welding is likely to fail. I found that Caterham rads were rubbish so got Coolex in Nottingham to make me a rad and the quality is far superior to anything else I've seen out there. Nice people and nice prices:

http://www.coolexperts.co.uk/

[rj]

Not all Caterham radiators are crap. Mine is more than 10 years old. I suspect that sometimes it's fitted in a way that stresses it - could be the hoses or the rubber bobbins that are not placed correctly.

 

[p.mole1]

That doesn't sound right I'd be surprised if you have managed to hole a forged piston unless one cylinder was running extremely lean and I would though it would have been making some horrendous pinking and detonation noises!

I don't think the radiator loosing it's coolant would cause a holed piston, especially a forged one, it would more likely cause an engine seizure. Are you sure your garage fitted forged pistons? 

[mic]

Radiators are unlikely to spring lots of leaks at one time, there would be some indication of coolant escaping if it was that bad.

[Highside43]

Thanks for the feedback, I'm an basic DIY mechanic but have to rely on garages / mechanics to repair my vehicles so have to take their word for it. The car was R/R'd to set it up a week or so before I collected it at Easter. I did report back that after driving home and out a few times that weekend it was running a little warm, say about 90 but not near the red. It was also struggling to tick over - sometimes it would just stall (mildly amusing the first couple of time, then annoying coupled with it's inability to start and the hassle of trying to bump start with a roof on....), or it would sit at 2100rpm with everyone looking at why I was about to do a GP start in the middle of a queue. They were Weisco (???) pistons on DVA con rods - I was future proofing the engine to allow me to take it to a goal of 200bhp when funds permit - it's cost 6K so far and I've ended up with a car worse than when I bought it, and unbeknown to me then it had a duff engine, hence why I spent so much trying to rectify it. It wasn't making any untoward noises to my knowledge though - no knocking or pinking.

[Slipper man]

The type of knocking that holes pistons is not normally audible. The car just seems to be holding back a bit. (Dont ask how I know!)

 

[oilyhands]

What is the CR like? If you are using Wossner pistons and the head has been skimmed then the resulting CR can be very high, this can cause pinking which may overheat the piston, the edges of the crown where the valve reliefs are can be very vulnerable.

Oily

[7 wonders of the world]

Also look at the injectors in particular debris / restriction in the filter baskets and if these are clear have them tested for pattern and flow, make sure you number them before removal so you can prove any results.

[Highside43]

OK, thanks folks.  I'll keep your comments in the memory bank and go back to the garage with them and see what the response will be - at the minute I was told catastrophic radiator failure was cause of piston hole and head to warp (again).

CR (I was told) was high when I collected the car, and also told to listen out for pinking but I couldn't hear any while driving it the 170 odd miles back home, or throughout the weekend.  I believe we are now using your pistons Oily?

Head is being skimmed again, so I assume a shim will have to be used as well as gasket to pack it up / out - will this reduce compression (in a positive way, if I had a lot before)?

[oilyhands]

I haven't supplied any of my pistons for a couple of months although I have had an enquiry or two.

A 1mm shim would certainly reduce the Cr, as would the use of istons with the correct crown height for the combustion chamber volume.

Oily

[Tazio]

Highside, , you refer to 'the garage', have you sure they have the competency to build a K series?, as blaming a rad failure seems to be a distraction technique....