Triton scanner

Last week snap on came round advising they were doing a deal on these scanners. He said are you interested! I said we'll discuss it next week, so he said I'll put your name on one. Yesterday he came round and I did not mention it. On the van I saw the boxed brand new delivery of the scanner. Interesting that anytime I ask for an order he has not got, it can take several months for him to get what I ask. Based on this and the last scanner I bought from him, which he charged me £2600, on an XP platform running 18.4 software, which has worked but is slow in operation, and was secondhand, yesterday I decided I didn't want to spent a few grand on yet another scanner that with experience will probably have poorly written software. By this I mean indepth coverage of the vehicle systems. Ebay is full of cheap scanners that seem to do so much more than the expensive stuff we buy from branded dealers, so I think for me anyway the time has arrived were buying top dollar equipment is at its end. 

A good few years back I started investing in Pico equipment, and I've got to say that an investment of around £10 000 is in order. Some of that investment was the NVH kit and the Pressure transducer master kit. I've been very impressed with the kit and not really got a bad word to say about it, and I've got to admit that the indepth abilities of the Pico software is above my head with some of the stuff it is capable of doing.

That said...

I've recently been investigating a cooling system fault on a Corsa D. The customer advised that the expansion tank would boil over and loose coolant. The first time I saw the Corsa do this I thought expansion cap! We bought one in and tried it and it seemed to be okay thereafter. A few days later the car was back with the same problem. We tried a thermostat. All hoses were hot and the heater blew hot and after a short road test and gaining operating temperature the fan cut in and all seemed okay. A few days later the car was back with the same problem. Scratching my head a bit now! I topped up the coolant and run the engine again and it seemed fine again. Last Friday the customer advised the engine overheated and can he bring it in! I asked him to bring it Monday this week.

Tuesday afternoon I got some spare time and did some tests on it. While the engine was cold I removed the spark plugs and using the pressure transducer in each cylinder I recorded the live data, which seemed the same for each cylinder. I then decided to put a spark plug in each ajacent cylinder to see if any difference could be seen from the waveforms, and I could not recognise any differences at all.

I then decided to run the engine at idle using the pressure transducer in each cylinder in turn. Each cylinder produced identical waveforms. During these tests I had my cooling system adapter in the expansion tank along with a temperature gauge. While the engine was warming up from cold, i.e. approximately 10 degrees C, I noticed the coolant starting to boil in the reservoir tank at around 40 degrees coolant temperature. I pointed this out to the other lads and one of them took a video snap of it boiling and the temperature. If I was high up Mount Everest I'd accept that boiling as normal at 40 degrees, but not in the garage at sea level or thereabouts.

Once the engine cooling system had cooled a while I decided to put the pressure transducer on the adapter on the reservoir. I ran the engine at idle for some 64 pages of data and in the last few pages the coolant started to boil and the waveform became very erractic, and the pressure increased towards 6 bar. Clearly there is no doubt that an internal leak is present, and yes you could say we all know the head gasket is leaking, but if that is so, why then does the waveform anaysis not show any difference between cylinders? Or does it but I'd not recognised it? Up to last night I was scratching my head because I knew the engine had a combustion leak, but I could not seem to see the evidence to support the claim! How many times in our life time have we said, yes the fault is? only to find later that it was something else! 

I inspected the spark plugs but found nothing. I looked into each cylinder with my boroscope and saw nothing obvious, even the head gasket sealing rings seemed okay as far as I could see it. I was left wondering if the cylinder head had an airline fracture that opened as the engine was warming up? How would I prove this?

I don't 100% know for sure if I can say this is the true cause of the fault...

I looked back on the pressure transducer waveforms and compared each running idle test. Nothing seemed to stand out, but then I thought while looking at the exhaust pockets and intake vacuum pockets, which looked about the same depths, I'll use the rulers and see what pressure of vacuum is present in each cylinder during the induction strokes. This is something that cannot be carried out using conventional test equipment like a vacuum gauge. 

I measured on cylinder (1) 695 millibar of pressure, and then on cylinder (2) 613 millibar, and 685 on cylinder (3) followed by cylinder (4) at 660. Clearly then something is a miss in cylinder (2). I can say for sure that cylinder (2) is low on the pull of vacuum, and I can also say for sure that the coolant pressure seriously increases to the point of blowing the reservoir cap off its seal to allow the escape of coolant, but can I say that the defective cylinder operation is caused by either a leaking cylinder head gasket sealing ring, or what might be an airline fracture in that cylinder combustion chamber or liner? 

In all my years of experience with engine faults of this nature I can only reflect on a couple of cylinder heads that had an airline fractures! The customer complained because he'd very recently had a cylinder head gasket renewed only to have the same problem after reassembly. Why then do these people not go back to the repairer? I've never understood this!

Once I'd removed the cylinder head off his engine and cleaned the combustion chambers I saw the airline fracture across the combustion chamber. (I can quite assure the readers with my eye sight today that would not be the case). After replacing the cylinder head the the engine cooling system was okay. 

Jumping to conclusions and saying the head gasket is leaking is not the same as proving the head gasket is the cause of the leak!

With regards the Corsa D diagnosis could I of done anything different or used a better diagnosis procedure?