504 oil pressure valve
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  1. #1
    Fellow Frogger!
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    Default 504 oil pressure valve

    I have a very small oil leak coming from the bottom of the oil pressure sensor valve, the one that screws into the oil filter housing and has a single wire running to it. I've taken the valve out and am puzzled by the fact that the little nut at the wire end of the valve (the one attached to a threaded shaft) seems to allow one to adjust the travel on the spring-loaded sensor, from quite a lot to essentially none. When a lot of travel is allowed, pushing the sensor in also pushes the threaded shaft out and i could definitely see how oil could leak around the washers. Do i have an adjustment problem or is this valve defective (it seems to function fine by the way except for the small leak)? If the former, what is the correct amount of play? thanks

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    russ

  2. #2
    1000+ Posts Wildebeest's Avatar
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    russ,
    The oil leak at the switch is via the threaded shaft.
    If you loosen the small nut [5mm ?] holding the wire connection then gently tighten the nut below it. This should eliminate the oil leak.

    I've never known any pressure adjustment being necessary.

  3. #3
    Too many posts! JohnW's Avatar
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    Quote Originally Posted by Wildebeest View Post
    russ,
    The oil leak at the switch is via the threaded shaft.
    If you loosen the small nut [5mm ?] holding the wire connection then gently tighten the nut below it. This should eliminate the oil leak.

    I've never known any pressure adjustment being necessary.
    Wildebeeste, it sounds to me as if he's already messed with it... So it may now be out of its original adjustment?
    JohnW

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  4. #4
    1000+ Posts Peter Chisholm's Avatar
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    As John says the components may in the wrong way around. I can't remember accuratley the order but I think there is a small fibre washer on the outside and a larger on the inside. Anyone?

    It is actually an oil pressure switch, not a valve.

  5. #5
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    Thanks for the responses. I've attached a photo of the switch below. In its current state, if one pushes the sensor (the left end that when installed sits in the oil filter housing) toward the threads, the spring will compress, the threaded shaft holding the washers and bolts will push out the other end, and oil will clearly have the opportunity to leak out. If I remove the outer nut (that holds the wire connection) and tighten the inner nut (while holding the threaded shaft), the sensor at the other end will compress the spring, snug up to the main threads, and the black rubber washers will compress against the outer hexagonal bolt head. I agree nothing will leak in this position but I'm confused as to what the spring does in the first place. I was assuming that the oil pressure pushed the sensor toward the body and that this broke the circuit and made the red oil light go out. At any rate I'm worried that running the inner nut all the way down the threaded shaft will stop the lead but also influence the extent504 oil pressure valve-oil-pressure-switch.jpg of pressure the switch is sensing?

  6. #6
    1000+ Posts Peter Chisholm's Avatar
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    I've never really thought about it I assume the spring disconnects the switch until there is sufficient oil pressure on the plunger to overcome it and complete the circuit.

    Just in case, the correct order from the inside is plunger, then spring with threaded shaft inside it, then spring with plastic tube inside spring with flare facing hexagonal body, then on the outside the fibre washer, metal washer and then locknut. So far as I know there's no adjustment, just tighten up the locknut -but not over zealously.

  7. #7
    Too many posts! JohnW's Avatar
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    Quote Originally Posted by rpieper View Post
    Thanks for the responses. I've attached a photo of the switch below. In its current state, if one pushes the sensor (the left end that when installed sits in the oil filter housing) toward the threads, the spring will compress, the threaded shaft holding the washers and bolts will push out the other end, and oil will clearly have the opportunity to leak out. If I remove the outer nut (that holds the wire connection) and tighten the inner nut (while holding the threaded shaft), the sensor at the other end will compress the spring, snug up to the main threads, and the black rubber washers will compress against the outer hexagonal bolt head. I agree nothing will leak in this position but I'm confused as to what the spring does in the first place. I was assuming that the oil pressure pushed the sensor toward the body and that this broke the circuit and made the red oil light go out. At any rate I'm worried that running the inner nut all the way down the threaded shaft will stop the lead but also influence the extentClick image for larger version. 

Name:	oil pressure switch.jpg 
Views:	162 
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ID:	61774 of pressure the switch is sensing?
    Ah, different from anything I've seen. I've no idea to be honest, but if that is the switch that Wildebeeste knows, he's most likely correct. You could rename him "wily beeste"..... Sorry for pun....
    JohnW

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  8. #8
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    Why not just get a new switch [9 euros from Franzose] .I got one recently to eliminate the oil leak

  9. #9
    1000+ Posts Peter Chisholm's Avatar
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    It's probably not necessary. I've never had one leak, it needs to assembled in the correct order. The outside nut should compress the outer fibre washer against the inner plastic sleeve thus stopping the oil leak.

  10. #10
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    I agree that a new switch is cheap and in fact have ordered a new one. I also agree however that if I tighten the inner nut it will push the washers up against the outer bolt more tightly and probably stop my leak- that's all good. I'm still really puzzled however as to why the sensor end is on a spring and why it looks like there needs to be some travel. Does that sensor end redirect oil flow as well as sense oil pressure? My concern is that with the inner nut tightened the play will be virtually eliminated i.e. the sensor will sit snug up against the body of the switch. Probably overthinking this but I'd just like to figure out how this oil circulation/pressure sensing works

  11. #11
    1000+ Posts Peter Chisholm's Avatar
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    It's a switch, either on or off. There is, I stand to be corrected, no inner nut and no adjustment. You are right, you're overthinking this. As I said before, with everythinh tight, I've never had a leak and I've had a lot of 'em.

    Anyone else?

  12. #12
    1000+ Posts Wildebeest's Avatar
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    Quote Originally Posted by Peter Chisholm View Post
    It's a switch, either on or off. There is, I stand to be corrected, no inner nut and no adjustment. You are right, you're overthinking this. As I said before, with everythinh tight, I've never had a leak and I've had a lot of 'em.

    Anyone else?
    Peter, I'll go along with that.
    They are an elaborate design, used on Peugeot from way back, 203's etc. The PRV6 also until they changed to the common, as we know it Jim, switch.

  13. #13
    Fellow Frogger! julian b's Avatar
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    It is a switch ,not a valve ,and its only function is to make the dashboard light come on when there is no oil pressure .

  14. #14
    1000+ Posts Peter Chisholm's Avatar
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    Just to complicate things, I think that if the the filter becomes blocked the movement of the piston-like part of the assembly exposes a gallery and bypasses the filter.

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