Originally Posted by Laguna II Owner
Bloody good point Badams I didn't fully explain that one at all ( **** it )
I am afraid the credit must go to Honest John who first reported this following feedback from the trade...
valve should open to allow carbon dioxide, which acts as a cooling gas) into the combustion chambers when the engine is under load (>30% boost). This allows the combustion chamber temperature to drop and thus the temperature of the exhaust gases. If it sticks in the closed position the exhaust gas temperature will rise causing a) the
bearings to fail and b) engine
into the induction system. This will cause the engine to go on running until it has consumed all its
and then it will go bang.Problems with
valves in Renault dCi engines are often the cause of rough running when the valve is stuck in the open position as well. In several cases turbos have blown but the
valve has not been replaced. Inevitably the new
unit will not last long. "
I believe that Honest John quotes from a piece that Antmat had written elsewhere and e-mailed to him. Antmat is also responsible for the technical input in the "AUTOEXPRESS" piece about problems with used cars titled "Hidden Horror Stories".
Garrett turbos are the most reliable in the world but if they are to operate in a safe and efficient manner then two things are required:
1. Clean air and
2. oils that will withstand the rigours of lubricating a bearing that supports a shaft spinning at more than 100,000 rpm!
I understand that Don of Performance Oils (AMSOIL UK Distributor) might be looking for someone with a Laguna ll 1.9dCi that is out of warranty who is prepared to run AMSOIL Euro spec and a supplementary filter. This is a good idea but I think that there might be a problem in finding a suitable take off point. An ideal test vehicle would be one that had just had a new (not refurbished)
and where the owner was going to be doing high mileages and keeping the car for some time.
Supplementary filters are frequently run in the States and there are factual accounts of engines running more than 100,000 miles without an
change. Of course the
is tested for its structural integrity every now and then!
valves are frequently mentioned and I would suggest that Antmat's piece on these valves (Parker's FAQ Forum) is posted somewhere on here. I am sure that he would be agreeable. Pierburg has introduced a modified valve for the dCi engine some time back with the object of reducing its sticking.
Power loss is usually down to the valve sticking open. It is this "stickiness" that can point to failing
passes through and makes its way into the induction system. Burnt
residue will condense in the
valve and cause it to stick open or closed. Sometimes a good blow out will raise the exhaust gas temperatures and temporarily relieve the sticky condition.
Renault has done much to try and alleviate the situation and this has helped the later cars. There should be no similar problems with the new 2.0l engine.