Sad day - welsh plug behind water pump - gone!
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Thread: Sad day - welsh plug behind water pump - gone!

  1. #1
    Fellow Frogger! Pug72's Avatar
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    Default Sad day - welsh plug behind water pump - gone!

    Hi all

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    Been spending some time on the 504 recently with new rear drive shaft boots (all four), new radiator, fan switch and thermostat, plus fixed the leaky automatic...but now went to change the water pump as it was leaking and discovered....no welsh plug! Well, it was there just floating around. There is a fair amount corrosion around the welsh plug seat so I know that the head will have to come off and get reconditioned.

    The last time this was done was in 1985! So I guess I can't complain.

    Now I'll have to get the car flat towed to the mechanics.....Sad day - welsh plug behind water pump - gone!-p504-missing-welsh-plug.jpgSad day - welsh plug behind water pump - gone!-p504-welsh-plug.jpg

  2. #2
    Real cars have hydraulics DoubleChevron's Avatar
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    The corrosion between the studs is interesting. I wonder what has caused that. Shouldn't you be able to just clean it all up and just fit new plugs

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    1000+ Posts Peter Chisholm's Avatar
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    Although there is green stuff evident in the pic, it looks as though the car has been run for a long time without any corrosion inhibitor. It's a bit hard to see form your photo, but repling it in situ would depend on whether or not there is a good lip with which the new welsh plug can bite into.

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    So what's caused all the rust corrosion? A lack of annual distilled water and a decent inhibitor replacement?

    Pavel

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    1000+ Posts robmac's Avatar
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    Quote Originally Posted by Pavel Moore View Post
    So what's caused all the rust corrosion? A lack of annual distilled water and a decent inhibitor replacement?

    Pavel
    Is the radiator still on the rubber mounts on both the upper and lower brackets?

    I've got a suspicion the radiator was electrically isolated from chassis to reduce electrolysis caused by the differential between the aluminium head and brass/copper radiator.

    A radiator as fitted by Mr Pug is isolated from ground.

    If the cylinder head is being welded (I suspect it may need it!) . Then consider having the dome plug behind the WP, replaced with a disk of 6 mm thick aluminium and tacked in placed with the TIG.

    This makes a permanent fix and saves rooting around try to hold a steel plug in place with tappers. (the retaining recess is probably corroded away) It may corrode a bit, but will definitely outlast anything made of ferrous metal.
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    The current thinking of manufacturers and coolant experts is to have the radiator electrically isolated, as far as possible, from the battery earth return circuit. As such many radiators have plastic top and bottom tanks that provide the mounting points and are therefore insulated from the chassis return circuit and are not provided with battery return paths. Most shop manuals, in these cases, stress the essential need to ensure that block and head earthing strap connections are maintained in first class condition to ensure electrolysis does not occur -- allied to regular coolant changes. Some coolant manufacturers even urge extra earth straps be fitted to the engine block.

    Pavel
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    Fellow Frogger! Pug72's Avatar
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    Hi all and thanks for your replies

    The radiator is sitting on rubber mounts.....and the top mount is rubber isolated as well.. The car has always had distilled water and coolant in the system so I don't know why there is so much corrosion. There is too much corrosion/scale build up around the welsh plug seal to ensure a perfect fit with a new welsh plug. The head will have to come off and get machined. I am worried that the further I dig the worse it will get.

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    1000+ Posts Beano's Avatar
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    If your head gasket is ok, (and you trust it, after seeing that corrosion) you can screw in another welsh plug without taking off the head. I've contributed to a thread on how to do it on this forum.
    It's fairly easy and straightforward. You use stainless steel screws.

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    1000+ Posts Wildebeest's Avatar
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    Much has been written here on this subject. Not one of Mr P's cleverest ideas. Why not a sacrificial plate being part of the water pump?

    Refitting a new plug, retaining with short stainless self tappers is OK.
    My head guy replaced the plug on my 504 head using Devcon. A product held in esteem by engineers.

    It is not necessary for the plug to be a 100% seal between the pump recess and the cyl. head.

    The "stray electric current" being a source of corrosion by latter day thinkers.
    I have run an earth cable from the head [thermo housing bolt] to a convenient bolt on the body behind the headlight.
    This was done on some earlier advice on Aussie Frogs. IMO I've had nothing to lose but may gain something?

  10. #10
    1000+ Posts Beano's Avatar
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    Those earth straps to the water pump are a great idea !
    However I'd much sooner trust a mechanical fix like screws, than Devcon. Basically it's an epoxy, and I had no luck fixing my plastic 206 fuel sender with an epoxy ribbon recently.

    Pug72...don't panic and expect the worst with corrosion just because of what you see there. It is not much worse than I've seen regularly. It does not mean the surface of the head will be the same.

    The thing is : if the head has not been off since the mid-eighties, you now have a good opportunity to make sure the head is good before Summer, by taking it off, shaving it (with very strict instructions to the machine shop to take off the absolute minimum), getting a valve grind, and putting in new valve stem seals.

    Find the thread here in which we describe screwing in a new welsh plug, or pay the machine shop to do it.

    Plus a new head gasket with a good layer of Hylomar sprayed on it. Trust me....it is a small price and small amount of extra work, for a big payout in terms of reliability.

    P.S : Be careful tightening those water pump studs. They get brittle with age. I usually replace em with new bolts (high tensile), which I screw in, then cut off the hex head so they are the correct length. The studs MAY be difficult to buy new, but the bolts are virtually the same. Get longer ones and trim em to size when you cut off the hex head.
    Last edited by Beano; 29th October 2014 at 02:16 PM.

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    Fellow Frogger! Pug72's Avatar
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    Thanks Beano for your advice.

    I don't have time to pull the head off myself so will get it trucked to a Peugeot mechanic in Brisbane.

    The car is a family heirloom and in mint condition so worth doing. I just hope the head is repairable. The head gasket is fine, but I know some of the other welsh plugs are getting soft.

    Definitely will convert to hardened valve seats so I can run on straight unleaded.

    Hopefully get the car to the mechanics tomorrow. I miss driving it already!!! My other car is a Landrover Defender 130 dual cab (fully kitted out) which is a bit of a pain driving around town.

    Thanks

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    1000+ Posts Peter Chisholm's Avatar
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    By the way, if you have the head off, the two big welsh plugs at the back are definately worth replacing, even if they look okay. They are sometimes very corroded on the inside bit look okay on the outside.

    Cheap and easy to replace with the head off. Impossible to do with the head still on.

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    Yep, all welsh plugs will be replaced in the head. Might even get the head ported and polished

    Cheers

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    1000+ Posts Beano's Avatar
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    The smaller welsh plugs in the side of the head will not need to be replaced. They do not cover any waterways....I think they cover the inlet port. But I agree....the 2 at the back of the head absolutely and definitely need to be replaced.

    I take it that you're kidding, but just in case you're thinking of it : Porting and polishing has been described to me as being an unnecessary expense and hardly affecting performance....on 504s.

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    Quote Originally Posted by Beano View Post
    The smaller welsh plugs in the side of the head will not need to be replaced. They do not cover any waterways....I think they cover the inlet port.
    i read somewhere that if you remove them you can fit a custom made inlet manifold.

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    Yeah, I was kidding Beano...for the amount of time spent with the die grinder for maybe 2-4 horsepower gain, its not worth it. Car is totally stock.

    My next thought is should I be replacing the liner seals whilst the head is off? I know it a big job to pull liners etc, but it's been nearly thirty years since they were done. Everyone's thoughts?

  17. #17
    1000+ Posts Peter Chisholm's Avatar
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    Yes, it's abig job. if you've been careful not to move the liners and if it's a 2L, I wouldn't bother changing the seals. With 1800cc the Neoprene (?) seals get hard with age and it could be worth replacing them. It all depends on how much time you have on your hands and how far you want to go.

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    1000+ Posts BIGRR's Avatar
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    Quote Originally Posted by Pug72 View Post
    Yeah, I was kidding Beano...for the amount of time spent with the die grinder for maybe 2-4 horsepower gain, its not worth it. Car is totally stock.

    My next thought is should I be replacing the liner seals whilst the head is off? I know it a big job to pull liners etc, but it's been nearly thirty years since they were done. Everyone's thoughts?
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    1000+ Posts driven's Avatar
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    Seems to be a common welsh plug problem with 504's. Never had one but

    A simple solution to me would be to cut an alloy plate to cover the welsh plug hole, with a hole for the water flow,
    a gasket between head and plate and just remount the water pump with second gasket as per usual.

    May need to check belt alignment.

    Easy does it no machining required

    My 1 Euro's worth or should that be Franc due to age of vehicle

  20. #20
    1000+ Posts Beano's Avatar
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    That's more or less what we are suggesting as an alternative to getting the machine shop to weld a plug in there...except it needs to be held in place with stainless steel self-tappers. (Don't even think of using anything but stainless ones....not because it's corrosion-resistant, but because they're REALLY tough. Ordinary ones break at the drop of a hat. And you need to screw it in hard, through solid metal).

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    are tin-tin screws used for drywall construction good?

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    1000+ Posts Peter Chisholm's Avatar
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    No, tin tin screws for plasterboard (drywall) are not suitable, they are not up to the job. Stainless steel are stainless steel all the way through and are therefore very strong. Beano's right, with anything less, the head of the screw will simply break off. Been there, done that.

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    1000+ Posts Beano's Avatar
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    2pac...please re-read my post above. Nothing else is suitable, except stainless screws. You are not screwing through sheet metal. You are screwing into solid metal.

    And (just as an aside) consequently the drill bit and hole need to be slightly bigger than you would think. Bigger than for sheet metal.

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    Hi All

    Things are not looking good....I can't even remove the fan hub assembly from the old water pump!!!!

    Any secrets to removing the fan hub? Obviously there is corrosion between the shaft and the bearing. Ive been using WD40 but reluctant to use heat.

    Worst case - can I still buy the fan hub?

  25. #25
    1000+ Posts Peter Chisholm's Avatar
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    I've never had a lot of trouble removing the fan hub from the water pump, and I've had dozens of them. No real suggestions other than what you've been doing. I wouldn't use heat, remember, that fan hub has a coil of wire inside and wouldn't like a lot of heat.

    You could try lightly tapping, via a centepunch, the end of the shaft while holding the fan hub. Be careful though, the fan hub is cast and will probably break if struck with a hammer.

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