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Thread: thermostat

  1. #1
    nJm
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    thermostat

    Drove my 505 up to Eildon today, which was great fun. One thing I did notice was that despite driving for over 3 hours, my engine still appeared to only be slightly warmed up. Recently I've noticed it appears to be running rich, and by going on today (temp guage did reach midpoint once, but then dropped again and stayed at about 1/4) I'd say my thermostat isn't working.

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    How much would the part cost, and how easy to install? I know that if I don't do it soon I could end up with a dead engine and I do not want that! dead
    Nick
    1983 Peugeot 505 GR


    "All of its cars from the 1.1 litre 205 through the ugly duckling 309 to the 2.2 litre 505 GTi had a rightness and a righteousness about them that turned every humdrum drive into a journey. Someone, I once wrote, in the bowels of Peugeot understands handling and how a chassis should feel." - Jeremy Clarkson

  2. #2
    Gus
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    Dead engine? eek! .

    My car's been like this for _ages_. In winter the temp gauge visibly drops up to a third when you hit the highway (which I drive 30km on each way to work/uni.) Most mornings the engine gets warm but never gets out of the bottom segment of the temp gauge.

    I kinda assumed the thermostat was jammed open, cos I'd heard the optimum temperature for a 505 was just above the midpoint on the gauge - but while I thought the slightly more viscous oil would lead to a bit more wear, and I knew fuel economy would suffer, I didn't know I could kill an engine this way. How does it die?

    Anyhow, a thermostat for a ZE(D?)JK engine (505STi) is ~$20-25 I think. Replacing it in these engines is a case of draining the coolant (you can just drain the first third or so if you want, but coolant goes "off" after 1-2 years so it may be worth changing it), taking off the extra air device from the top of the thermostat housing (easy) then unbolting the thermostat cover (this is where I stopped last time I did it, I was only going to do it cos I had the coolant drained and the radiator out, and the bolt at the back is in a _bastard_ of a spot to get at with either a spanner or any of my sockets... so, in true half-assed fashion, I gave up.)

    On a GR/SR I presume the thermostat will be very different but probably similar cost/job difficulty. On the GTi it should be in the same place but may have more (or less) fuel injection gizmos bolted on and around it( wink ).

  3. #3
    Gus
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    Oops, I missed you had a GR (didn't see it in your sig.)

    OK, my Haynes manual (an invaluable resource if a little wrong sometimes) sez:

    1) "The thermostat housing on carburettor engines is integral with the water pump, located on the front of the cylinder head."

    OK, then.

    2. Drain the cooling system as described...

    3. Disconnect the radiator top hose from the thermostat housing.

    4. Unscrew and remove the two thermostat housing cover bolts, and remove the cover. This may need to be tapped slightly with a wooden or plastic-faced mallet to free it.

    5. Remove the thermostat. If it is stuck, use a sharp knife to cut the rubber seal from the housing.

    6. Ease the rubber seal from the edge of the thermostat.

    (The book now describes how to test a thermostat by suspending it in water and heating the water. I presume if it's jammed open this will be evident just by looking at it cold!)

    Thermostat in a carbie engine is expected to start opening at either 75 or 82 degrees and be fully open (7.5mm)at 95 degrees

    ...

    10. Fit the rubber seal on the thermostat flange, noting the tab locates in the seal extension on carburettor engines.

    11. Locate the thermostat in the housing.

    12. Clean the mating surfaces, then fit the cover and tighten the bolts.

    13. Reconnect the radiator top hose and refill the system as described.

    ... doesn't sound like rocket science.

    Incidently, the mighty Haynes also says to torque the thermostat housing bolts to 15Nm. This probably isn't too important if you don't own a torque wrench, just make it tight enough that it won't leak without making it so tight that it strips the threads. (Read: she'll be right :p )

  4. #4
    nJm
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    Thank you!!!

    I'll do it next week.

    Yes, I was under the impression that if a car's thermostat was broken, not allowing the engine to warm up could lead to it dying. Basically, it doesn't warm up = runs rich, rough, higher emissions and can lead to cracked cylinder heads ( or is it just the head question question ) etc. I don't know much about it, a friend was describing it to me.
    Nick
    1983 Peugeot 505 GR


    "All of its cars from the 1.1 litre 205 through the ugly duckling 309 to the 2.2 litre 505 GTi had a rightness and a righteousness about them that turned every humdrum drive into a journey. Someone, I once wrote, in the bowels of Peugeot understands handling and how a chassis should feel." - Jeremy Clarkson

  5. #5
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    This is a very basic process on the 505 Gr engines. The engine is designed to operate at a certain temp which should be half way on the temp guage (you dont want it hot, but you dont want it to be cold). It takes 5 min to change a thermostat!
    JoFuS

  6. #6
    1000+ Posts tekkie's Avatar
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    nJm

    Im not a mechanic butI fail to see how you can kill an engine by running it cold. It will be a fuel guzzler, the engine pipe will never look blacker and dirty, the cylinder walls will become nicely caked with fuel deposits ( increased compression ? wink ) and there will be pressure points due to high temp differential between cylinder walls and the rest of the engine. VL commodor... ( oops nearly swore ) had problems with alloy cylinder heads warping/cracking but that was from massive overheating when coolant ran out. I wouldnt imagine that running car cold will kill the engine.

    Anyone else can explain to me how?

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  7. #7
    Budding Architect ???? pugrambo's Avatar
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    my brother in law had a VC V8 commode that he used to drive from one side of town tho the other for work everyday
    he used to also take it for a good run out of town as well but because the car ran cold most of the time it ended up with tapered bores and the head became all coked up from carbon
    as far as i know engines are designed to run at a certain temperature for certain reasons to reduce the amount of wear in the cylinders and to run efficiently
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  8. #8
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    Long term, an engine running cold would have to lead to problems. As pointed out, they are designed to run at a certain temp. Having a rich mixture in an engine cannot be good. Surely the Gas Guzzling factor would be enough to make you want to keep the engine at its correct tempreture? mallet
    Jason Judd
    <img border="0" alt="[Peugeot Emblem]" title="" src="graemlins/peugeot.gif" /> '85 505 GTi Executive
    <img border="0" alt="[Peugeot Emblem]" title="" src="graemlins/peugeot.gif" /> '88 205 GL 1.1

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