AKE V6 TDI: Low Compression Issues

Hello,

habe an einem V6 TDI mit typischem Defekt am Ventiltrieb, Schlepphebel und Hydros gebrochen, Nockenwellen teilweise eingelaufen. Also alles runter, zur Sicherheit auch die Zylinderköpfe, alle Ventile ersetzt, Hydros, Hebel und die Nocken, also das volle Programm. Habe jetzt das Symptom, das nicht alle Zylinder die volle Kompression haben, folglich läuft der Haufen auch nicht an, die VP44 ist ja eh sehr empfindlich auf Luft, was das schlechte Startverhalten noch weiter begünstigt. Zuerst hatte ich die Hydros in Verdacht, da diese sich sehr schwer zusammendrücken ließen, diese wurden nochmals durch originale von INA ersetzt, seltsamerweise, wurde die Kompression auf einigen Zylindern besser, aber zwei von sechs haben immer noch 0,00 Bar. Die Ventile wurden bei abgebauten Zylinderköpfen und demontierten Nockenwellen mit eine Dichtigkeitstester mit Vakuum geprüft und waren alle absolut dicht. Die Problematik mit klemmendem Überdruckventil in der Ölpumpe und dadurch resultierenden zu hohen Öldruck betrifft diesen Motortyp nicht. EinAnother assumption was whether the hydraulic system could exhibit such a malfunction due to an oil viscosity that is too high for the specified standard of 10W40.
Has anyone else perhaps experienced a similar problem?

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The valves were tested for leakage using a vacuum tester on disassembled cylinder heads and with the camshafts removed, and they were all absolutely leak-tight.

I checked the spark plug well using a thumb test and gasoline. What kind of leak tester is this?
Regardless, maybe the hydraulic lines are too long and causing it to stick? Disconnect them and bleed them first. The oil pump shouldn't be generating too much pressure when starting.
hg
Herbert.

The vacuum tester was a useful tool for engine restoration. The oil pressure when starting is approximately 3 bar at around 150-200 revolutions, which I personally find a bit too high. What do you think?

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Initially, I suspected the hydraulic lifters, as they were very difficult to compress. I replaced them with original INA units, and surprisingly, the compression improved on some cylinders, but two out of six still show 0.00 bar.

What manufacturer are the NW (presumably referring to a specific part) and the rocker arm from? Are all the parts dimensionally consistent and of the same design?

After assembly, it's best to avoid starting the engine for a while, allowing the hydraulic lifters to settle and preventing any contact between them and the pistons.

10W40 isn't exactly ideal... I don't even think it's approved for use.

For example, some Ford engines used to have engines that would push the valves open when using 10W/40 motor oil.

Autoservice wrote:

10W40 is, of course, not exactly ideal..... I believe it's not even approved.

10W-40 is both approved (505.00 is merely required) and perfectly fine for the engines.
Until not so long ago, I still had two customers running V6 TDI engines that had been using 10W-40 oil for years.

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Only 505.00 is required

.

Okay, that's why I wrote "I believe" ... although for a quick lubrication of cold engines, oils like 5/40, for example, are better suited.

I only use this oil in really old vehicles... and in the lawnmower.

AKE units are likely to be "older" by now.