DS thermostat woes
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Thread: DS thermostat woes

  1. #1
    mnm
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    Default DS thermostat woes

    Hi all

    driving to work the other day and the thermostat doesn't open when it should... temp guage goes up and up.. red lights come on, etc... then suddenly opens and temp falls back to normal quickly. The drive home is all normal.

    Yesterday, same thing happens... set out, engine warms up....and up! Thermostat not opening... Pull over and remove said piece of crap to drive home.

    I tested the thermostat on the stove and it is opening normally in hot water. So, any suggestions why it is playing up? I have spares so easy enough to stick in a new one but curious to know what caused it to stick.

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    Thanks

    Matthew

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    Contented Peugeot Driver addo's Avatar
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    Is your water pump impeller working correctly?

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    Does it have a mechanical or an electric cooling fan?
    JohnW

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    mnm
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    Water pump is less than 12 months old but will check.

    Mechanical fan.

    I have a temp gauge so I can see when the thermostat normally opens... has been very predictable up till now.

    Matthew

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    Too many posts! JohnW's Avatar
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    Odd when things suddenly change, isn't it.

    My CX has been steadily rising to too high a temperature, irregularly though. After changing the thermostat to no effect, it seems to be one electric fan out of two not working.

    You'd wonder whether the thermostat is sticking even if it behaved once in a saucepan. Does it have a hole drilled to let a bit of water flow past it before it opens?

    Good luck.
    JohnW

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    Quote Originally Posted by mnm View Post
    Hi all

    driving to work the other day and the thermostat doesn't open when it should... temp guage goes up and up.. red lights come on, etc... then suddenly opens and temp falls back to normal quickly. The drive home is all normal.

    Yesterday, same thing happens... set out, engine warms up....and up! Thermostat not opening... Pull over and remove said piece of crap to drive home.

    I tested the thermostat on the stove and it is opening normally in hot water. So, any suggestions why it is playing up? I have spares so easy enough to stick in a new one but curious to know what caused it to stick.

    Thanks

    Matthew
    Just a passing thought Matthew. . .
    Have you fitted a filter at the top hose to radiator (a good thing to do) these do require regular maintenance and if partially blocked could give the symptoms you describe.

    Cheers
    Chris
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    It eould be good to have a photo of that hose inside as blockage sounds bang on, the remedy is panty hose over the hose is it not?

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    mnm
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    Quote Originally Posted by GreenBlood View Post
    Just a passing thought Matthew. . .
    Have you fitted a filter at the top hose to radiator (a good thing to do) these do require regular maintenance and if partially blocked could give the symptoms you describe.

    Cheers
    Chris
    No I haven't Chris. Will add that to the to do list. I just went and topped up the radiator and ran the engine without a thermostat fitted... the pump is definately operating properly. Before I filled it I noticed a few loose particles on the of the radiator holes...so will follow your suggestion Chris before the new thermostat goes back in.

    Next question.... it runs a 75 degree thermostat as standard. What difference does the higher temp. ones make?

    Thansk guys

    Matthew

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    Hi Mathew
    Is the thermostat in the top hose or the Water Pump housing,if its in the top hose I fond it helps to drill a small hole in it,say 4mm to permit a small flow when the stat is closed and thus worm it up quicker.
    Woody
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    Is the thermostat in the right way?
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    Quote Originally Posted by mnm View Post
    No I haven't Chris. Will add that to the to do list. I just went and topped up the radiator and ran the engine without a thermostat fitted... the pump is definately operating properly. Before I filled it I noticed a few loose particles on the of the radiator holes...so will follow your suggestion Chris before the new thermostat goes back in.

    Next question.... it runs a 75 degree thermostat as standard. What difference does the higher temp. ones make?

    Thansk guys

    Matthew
    I think you have diagnosed the problem, you are to be applauded for your roadside fix - many would have called for assistance (tow truck) or continued driving and risked cooking the motor. . .

    Thermostats do go AWOL, boring task only looking forward to opening and closing a couple of times a day. . . I would drain and keep coolant, backfush as best you can, fit a new thermostat refill and take a test drive.

    Being a little OCD (apparently) I would stay with the 75 degree stat.

    Cheers
    Chris
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    The Déesse has all the characteristics of one of those objects fallen from another universe that fed the mania for novelty in the eighteenth century and a similar mania expressed by modern science fiction: the Déesse is first and foremost the new Nautilus.

    (Umberto Eco [Ed], The History of Beauty, Rizzoli, NY, 2004)

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    Quote Originally Posted by brian woodcock View Post
    Hi Mathew
    Is the thermostat in the top hose or the Water Pump housing,if its in the top hose I fond it helps to drill a small hole in it,say 4mm to permit a small flow when the stat is closed and thus worm it up quicker.
    Woody
    I reckon, possibly more importantly, that the little hole allows the hot water from the engine to move towards the thermostat and start the process of warming up the thermostat.
    JohnW

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    Quote Originally Posted by Lasya View Post
    Is the thermostat in the right way?
    Yes, pay attention to this.....

    Because the thermostat is mounted in the hose, it is possible to fit it upside down.

    The element of the thermostat needs to be downwards.... ie in the hot coolant, not up in the hose.

    The correct thermostat comes with a small hole, to allow air bleed during filling.

    Bob

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    mnm
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    Here's the thermostat... there appears to be a small indent in the side of the rim... there's no hole anywhere else. From memory I had the spring end pointing downwards into the coolant. Is that correct?




    Matthew

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    The thermostat was working fine until something changed, so it all points to a flake of crud blocking the small bypass indentation.
    The panty hose leg slipped over the top inlet to the radiator with 6" of it pushed through and the hose pushed over to secure it is essential to stop the radiator core from blocking over time. Of course it should be cleaned regularly & replaced at the first sign of deterioration.

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    Quote Originally Posted by mnm View Post
    Here's the thermostat... there appears to be a small indent in the side of the rim... there's no hole anywhere else. From memory I had the spring end pointing downwards into the coolant. Is that correct?

    Matthew
    Sounds right Matthew, yours is the type that fits to the top hose yes. . .



    The other type that fits to the waterpump housing can be seen here
    Citroen DS Restoration: Thermostat



    Cheers
    Chris
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    "Déesse" Roland Barthes, 'Mythologies', 1957

    The Déesse has all the characteristics of one of those objects fallen from another universe that fed the mania for novelty in the eighteenth century and a similar mania expressed by modern science fiction: the Déesse is first and foremost the new Nautilus.

    (Umberto Eco [Ed], The History of Beauty, Rizzoli, NY, 2004)

  17. #17
    mnm
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    Yes it's the hose type fitting. I don't understand how the blocked bypass hole would stop it opening though. The thermostat is in the hot coolant which triggers it to open... what difference does the weep hole make on the other side of the thermostat?

    Matthew

  18. #18
    mnm
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    Do I need to do this?



    Is this the best project car you have ever seen?

    Matthew

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    Personally, I would drill those holes and have drilled my CX thermostats, but I don't have a DS so shouldn't be giving you advice perhaps.

    I think what those holes do is to allow enough coolant flow for the thermostat to progressively get warm with coolant moving past it even when it is closed. Otherwise it can only warm up by convection, and may suddenly get a slug of heat when the block is hot enough for the convective process to operate - pretty much what you were observing.
    JohnW

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    If the "weep" hole is blocked there will be no water circulating to encourage the thermostat to start opening. Eventually, by thermo syphon & possibly local boiling , enough hot water reaches the bimetal coil, or wax capsule to start it opening when it gets a rush of hot water, thus the sudden results reported.
    Hope your problem is solved.
    Richard

  21. #21
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    Hi Matthew,

    Just change the thermostat - its stuffed... they get sticky with age.

    Go the ladies stocking in the top hose - best advice I got some many years back.

    Cheers,

    Mark...

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