TAMD30A overheating

[plug1]

Anyone know please what the small(ish) diameter so called "vent" pipe does that goes between the heat exchanger fresh water resevoir and the turbocharger casing on the TAMD 30A?? I have been experiencing gradual overheating at speeds much above 3300rpm, and sustained speeds in excess of 3500 rpm have resulted in the engine coming to a stop with coolant being forced out the heat exchanger filler cap. The temp gauge registered appx 95 at this point and no temp alarm sounded. No fuel blockage apparent with clean filters and no water in the filter bowl. Just hope that it did not seize up....the engine ran OK again after letting it cool down.
I have removed and cleaned out the aftercooler and heat exchanger elements and found old impellor blade debris in the aftercooler as well as a badly restricted exhaust injection elbow. As part of the inspection I wondered what the above vent pipe does.

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[TargaLout]

It is a vent pipe from the turbo to the Thermostat housing. Later Volvo engines it is routed via the header/expansion tank back to the thermostat housing and not via the header/expansion tank but directly on earlier engines.
This is because the Turbo is mounted fairly high on the engine and vents the coolant chamber in the turbo back to the thermostat housing again normally the highest point on the engine.

cant see this being the reason for the overheat though?


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[plug1]

Thanks for the info....I hope that clearing the debris in the heat exchanger elements and opening up the exhaust elbow will fix the overheating pblm. Probably will check the exhaust itself to see if any debris is in there that may be causing excessive backpressure.



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