Oil pressure failure at hightemperature

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Oil pressure failure at hightemperature

Post by schomosport »

Took newly built Vauxhall XE to Snetterton yesterday to run-in and test and experienced a collapse in oil pressure after about 8 laps. I was only running about 5500 rpm but oil pressure fell rapidly from mid-50s psi to less than 10psi over half a lap before pitting. It was also accompanied by a significant oil leak although it is not clear if the two are related. Cleaned it all up and let it cool down and went out again but the problem reoccurred so we called it a day. Same problem, leaking oil and low pressure. This cannot be replicated in the paddock - the hot engine ex-track with 5 minutes to cool down gives 50-ish psi with coolant temperatures up to 100C without leaking so I am a bit stumped as to where to start looking since the problems only arise under load.

Suggestions welcome. Oil pump is a Speiss - does anyone have a diagram for this pump, I am just wondering if I have done something stupid when I reassembled the pressure relief valve. It look like it will all have to come apart again anyway since second time out there was a lot of vibration so it may already have run a bearing. Thanks.

Mark Schofield

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Nick Harrison
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Re: Oil pressure failure at hightemperature

Post by Nick Harrison »


On a Toyota installation we have had a similar problem on more than one occasion and it has been a broken pressure relief valve spring. They usually break in the centre and the two halves of the spring wind themselves into each other thus exacerbating the issue. Quick fix at the circuit is to turn the two halves round so the flat ground ends of the spring face each other.

We have also had the relief valve jam in a brand new pump through a little bit of swarf in the bore. In our case it jammed closed but I guess it could equally well jam open.


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