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Oil Pressure Relief Valve Service

 

With time and miles the pressure relief valve can become a bit worn and scored.

It can collect various debri from the engine which could make it "sticky" in operation.

Having seen valves which were not operating as smoothy as I would expect (that is not to say 

they were'nt controlling pressure as the should) as a precaution I removed mine for a clean up.

 

The valve assembly is located at the bottom of the front timing cover. The valve can actually be removed 

without taking the complete assembly off. I prefer to remove the whole assembly so that it can be cleaned 

properly and any burrs or scoring treated appropriately.

 

 

Remove the six cap head screws and lower the cover carefully because the pump gears will probably fall 

out at the same time. Be sure to note which way up the gears are fitted so that they go back the same way.

 

There is a wear limit for the mesh between cogs, I've yet to come accross any that were outside the limits, 

in any case new gears are no longer available and not wanting something else to worry about, these are 

going back in again.  :-)

 

The threads are standard M6 form, and cleaned up easily, they were a little gummed up with sealer.

 

 

Remove the circlip.

 

The valve will not fall out, it will need a little bit of educating, tapping the end on the bench will bring the 

retaining cap forward enough to remove it. The retaining cap has an o ring fitted to it.

 

 

 

 

 

The valve spindle was not badly scored although when checking the movement in the housing it was not 

at all smooth.

 

 

It does not appear to be a precision ground component, after some work with 1500 grit (used) wet and dry 

paper......just the burrs and roughness were removed.

 

 

 

Next was a look at the bore of the housing.

Again the machining is not really precision stuff, using same (used) wet and dry paper wrapped around a 

long series 13mm socket, I carefully slid this inside the bore and rotated and slid up and down until some 

but not all the scoring was smoother. (liberal amounts of wd40 helps too). The objective it NOT to remove surface 

material, just to reduce the scoring and remove any high spots !

 

Fit was checked and now the valve slides nicely within the bore. 

 

 

 

 

Next was to lap the mating surface using a new sheet  of 1500 grit  wet and dry paper on a surface plate.

It does not take long at all, perhaps only 20 secs or so circular motion. Lots of wd40 !

 

The surface was restored easily, in fact it might even be a bit too smooth....time will tell.

 

 

 

 

Re-assemble the valve, can be a little tricky to get the retaining cap pressed whilst replacing the circlip, I used 

a large g clamp to help this. Graphogen is my favourite for this, very thick and provides good protection whilst 

initial oil pressure is built up.

 

Special sealer for the pump cover mating face. 

 

Aswell as graphogen paste. I topped up the valve cavity with oil.

 

Graphogen was smeared on the pump gears, because the paste is really thick and sticky, the gears stayed 

in place whilst the cover was put back on.

 

Once all bolted back on, remove the oil pressure sensor and with a long spout fill squirt oil into the hole until 

it starts to pour out again, thus priming the oil pump. Refit the sensor.

 

Crank engine without the fuel pump running to build the oil pressure up before starting properly (watch for oil 

light extinguishing on dash)  job done.

Difference ?.....absolutely none, but then I never expected any difference to be honest, however I can be more 

confident that the relief valve won't give me any trouble in future.

 

Update Aug 2009 - I have noticed that when cold starting  the tappets settle down much faster than before,

so this job was worth the effort imho.

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