Posted by: motorvationsaab | April 12, 2013

Saab 9-3 Petrol Engine B207. Low Oil Pressure

Engine 2

 A puzzling problem with low oil pressure on a B207 petrol engine.

We recently had a 9-3 arrive with the customer complaining of a loud noise, especially on cold startup. We replaced a very noisy belt tensioner and the problem was resolved. However we could still hear a very faint noise from the cam chain area and suspected a possible problem with the cam/balancer chain assemblies.

On running the engine whilst trying to diagnose the noise we found that once at full heat the oil warning light was starting to flicker on. Checking the actual oil pressure we were surprised to find that it varied with subsequent engine startups which was rather baffling. On speaking to the customer they said that they had not experienced any problems ! This seemed even more odd, until, during the conversation it transpired that the car was rarely used, and when used, never went more than very short distances of a mile or so, thus never really getting to full heat especially given the recent cold weather. In the past we have had issues with debris in the sumps of cars that are rarely used, so we suspected sludging in the sump.

IMG_0725

Oil strainer and broken guide. Note the piece of guide sitting in the strainer

On removing the sump we found that a large piece of one of the balancer chain guides had been sucked up into the oil strainer. The larger of the two pieces was loose enough to move into different positions sometimes almost completely blocking the uptake of oil and sometimes only partially restricting the strainer.

Balance chain tensioner arm showing damage from chain running directly on arm. New and old profiles illustrated.

Balance chain tensioner arm showing damage from chain running directly on arm. New and old profiles illustrated.

Once the timing chest was removed it was plain that the tensioner guide had self-destructed and the chain had been running on the end of the tensioner arm.

As is shown in this picture the chain had effectively worn a “reverse” profile on the end of the arm.

On checking the Big Ends for possible lack of lubrication they were, remarkably, found to be undamaged. Replacement of the tensioner, chain and guides along with a thorough sump clean resored the car to good and consistent oil pressure and the engine undamaged.

So how did this happen ?

The truth is we can only come up with theories as to why the problem occurred. The tensioner is partly oil pressurised and in the initial startup there is a small element of “chatter” whilst the tensioner is brought to full tension.
It is of course speculation. However it is possible that since the car was driven only short distances and usually cold that over a period of time this “chatter” weakened the guide that is supported by the tensioner.

Another element in this case is the fact that the oil, when originally removed was relatively “gloopy”suggesting that, whilst the car has a service history from various garages, it is possible that the incorrect oil had been used and, or, had suffered from contamination due to the repeated short, cold engine,driving .

My theory above is speculation and in this case we can’t rule out a mechanical or manufacturing fault. The moral of the story is as always change your oil regularily with the correct type, and, if you use your car rarely or for short hops only, consider at least a minimum of annual oil changes. If you hear a “new” noise, get it checked. In this case, luckily, there were no further consequences, however it could have been very different.

Visit us at www.motorvationsaab.co.uk or call us on 01892 825208.

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Responses

  1. As the owner of the above saab, i would like to give a big thank you to chris and his team for an excellant job they done on my car although a bit time consuming i cant thank you enough for all your help. My car feels like its running on air im so grateful and would not hesitate to recommend motorvation saab to anyone. thanks again

    Like


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