Skoda Rally Blog

So, last time out, I had an engine that ran well, but didn’t have much in the way of oil pressure, particularly when hot.  Not great, and clearly needing sorting out.  I’d asked about and had some info from Jim Jones (who knows pretty much everything about Skodas) who said he suspected the pressure relief valve or the way the pickup was seated on the oil pump body.  After finishing work today I thought I’d make a start on checking out what was going on.  First up, the sump needed to come off; as it had only been on there for half an hour of running or so it came off without issue once the oil had been drained, revealing the bottom end in all its glory.  I thought it was best to check all the bearings, and this can be done with Platigauge which allows you to accurately measure the bearing clearance – it’s like a thin strip of plasticine which you put in the bearing shell, bolt it up tight and then undo it, and measure how wide it has spread against a measuring sheet to see what the clearance was.  The Skoda engine has 7 bearings in total – 3 main bearings and 4 big ends, and all the mains checked out OK, and big ends 1,2 and 3 did too, but No. 4 looked to have got a bit hot – it wasn’t terrible, but the bearing looked pretty worn.  The crank looked fine, and amazingly (again!) I had 2 suitably-sized big end bearings in my box of bearings (from previous engines), and they fitted perfectly.  Phew.

So, it looks as if the crank bearings are all fine, so why the low pressure?  Well, now I seem to have removed the need to take the engine out, it was time to look at the pressure relief valve.  This is part of the pickup on the 136 engine, and consists of a ball bearing and a spring – the bearing seals a port in the oil pump, and once the pressure gets too much then the spring lets the excess pressure out.  If this valve leaks, then the engine will not have good pressure at idle, as that low down it needs as much pressure as it can get and can’t afford to leak any.  So, I took it apart, and it looks as if the sealing area where the ball seats is rough – indeed it wouldn’t hold my breath when I tried to blow through it, even with the spring pressing hard against it, so hardly likely to resist much in the way of oil flow, I’d hope.

Either way, I have a new pickup and oil pump body arriving tomorrow, so hopefully when I put the spring and ball bearing into that, it will stop the flow, and in that case, it may well do the trick.  Here’s hoping…