Tech Tip: Water contamination a possibility
I am sure that any of us in the converter business have heard that statement; in this case the converter was a ZF 5HP19 of the captive clutch type fitted to an Audi AWD. We had overhauled the converter in question about a month before and now my customer, who was a transmission rebuilder in another town about 350 miles away claimed that the converter shuddered during the regulation phase. As always my first question was what fluid have you used in this? Answer was “Dexron 3” so I suggested that he might like to change to either the correct specification fluid or an equivalent. This he did and reported that the shudder was now gone.
About three weeks later he called again with the statement that the converter was once again shuddering. At this stage I decided that there was no real answer apart from to get the unit back and check it. This was done and the converter split. There was no evidence of any problem so I advised him of this and suggested that he check the transmission carefully. The converter was assembled with new lining and extra care on the clearances. It was fitted and the report was that the shudder was once again gone.
This time it was about a month and he reported that his customer was once again complaining of a shudder, he had tried another valve body and was now squarely blaming the converter. He suggested that perhaps he should send the converter to another rebuilder because it appeared that we were not having any luck and the competitor assured him that he would be able to do the job with success. I was reluctant to allow this to happen, as he is a good customer so after asking various people and hearing that often the fault could only be cured with a factory converter I offered to obtain a factory unit for him.
The factory unit arrived and was fitted; vehicle drove well with no shudder. This time once again for about a month and the customer is back once again with the same complaint. At this stage I said that I was out of ideas and the only way that I could help him was to have the vehicle. I should mention here that we are also a transmission shop. Vehicle arrived and sure enough it had one of the worst shudders that I have ever felt in a converter. We checked the obvious external things such as engine codes etc and then removed the pan. This is where it gets interesting. The technician that removed the pan reported that the fluid had a strange look to it. Not pink or discolored but “Just doesn’t look right”
At this stage I remembered that at the last TCRA seminar there was a brief mention of testing for water using a coffee maker of the filter type. A drop of the fluid on the hot plate and it sizzled. A sure sign of water. A report to a disbelieving customer that the fluid was contaminated with water meant we had to have a professional test carried out and this came back with 2% water contamination. Converter rebuilt with new lining transmission rebuilt with new clutches, refitted to vehicle along with a new radiator and all is well. It turned out that the radiator was leaking coolant into the fluid, not a lot but just enough to change the frictional characteristic of the fluid. Of course each time the fluid was changed the problem was gone until the contamination reached the critical level again.
So what is the moral of the story? Think outside the square don’t take anything for granted and remember the quick and easy test for water. Just put a drop on the hotplate of the coffee maker, if it sizzles and spits there is likely to be water contamination and if it just smokes the fluid is ok. Remember the fluid can look good and still be contaminated. Of course the best part of this whole story is that I retained my customer and was paid for all the converters and the transmission job as well as a radiator!
Aceomatic Transmission Services
Christchurch, New Zealand
– Found in June 2008 Newsletter