how to change the thermostat

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jacko
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how to change the thermostat

Post by jacko » Mon Dec 29, 2008 11:17 pm

work in progress
pics coming soon

the thermostat opens at a set temperature (usually stamped on it!) (can be tested by placing in a freshly boiled kettle) and allows coolant to the radiator when the engine (coolant) becomes hot. sounds boring but dont forget the internal combustion engine is 30% efficient. the other 70% is HEAT and some noise. so that little thermostat is coping with approx 300bhp of heat in an frp at full chat!!!!!!

it lives under the inlet manifold next to / under the alternator and is a complete *&(%$&* to get to! esp if youv got aircon. it feeds 2 pipes; one to the radiator and a smaller one to the heater control valve from a plastic (yep! be careful!) manifold. the hcv pipe bypasses the 'stat.

iv found it best to use ford parts as others dont always have a thick enough rubber gasket (useful!), its under a tenner and a few hours with plenty of cups of tea. its not very hard just fiddly!

is the stat faulty?
if its died & stuck closed you will fry your engine & the radiator will be freezing to touch
if its died & its open lucky you cos its just bad mpg rather than a fried engine! engine temp will be in lower readings always and radiator will be warm almost instantly.....

OH DEAR GOD! youve just noticed the gauge is in the red!!!!!!!! TURN OFF ENGINE & pull over ASAP.....ASAP!!!! undo coolant cap a little (CAREFUL OF BURNS, VERY CAREFUL). do not let liquid escape, undo a little more etc etc, remove oil cap too......you want to allow the engine to cool asap but SLOWLY. with an alloy head and block if they cool down slowly together and you keep your fingers crossed the head gasket will be fine..... DO NOT THROW WATER ON THE ENGINE.

the puma temp gauge should always be bang on in the middle within 10mins of running the car; if not keep an eye on it as it might be giving you notice of the stat dying.....(sometimes a dead hcv can play with the gauge tho but god only knows how!)

emergency? remove stat; keep outer casing but rip out inner 'switch'; replace.....car will run fine (cold & bad mpg but will get you where your going)


TO REMOVE;

locate

remove drivers side light to aid access
undo radiator cradle and allow to hang (allows small movement of radiator to get to fiddly bits
remove alternator!
(remove belt cover(under car), lock tensioner with spanners & take up slack in belt; careful not to be too hard as you will shear the tensioner off!
do a drawing of the belt for refitting later

5845

wiggle belt off, undo positive terminal on battery, undo alternator plug and bolt on positive feed, remove alternator top bolts x2; tilt right hand down & pull out wiggling past other parts)

if theres a 3rd bolt you may need to lower / release the radiator (so u can move it a little) it sits on a cradle under the car behind bumper....2 bolts hold it to chassis rail at either end....pop it off, let rad hang loose & should giv u plenty of room
when refitting get a friend to help u locate rad at holes in slam panel while u locate & bolt cradle back on....

piccy; thermostat housing

5847

remove hoseclips with pliers / maul grips, remove hoses & catch coolant. do not reuse and discard of properly (sorry i dont know where...anyone?)
what does the coolant look like? if it has an oily film then it could be bad news for your head gasket.

undo 4x 10mm bolts

5846

remove old stat noting which way round it goes....
check stat and seal against new one....
fit new one

make sure seal in plastic manifold is good & clean

refit

piccy; correct layout of aux belt on a 1.7 with aircon

5844

to get the belt back on use a little 'persuasion' and push the belt onto the crank pulley whilst using a 19mm spanner to turn the crank (always tighten).....will slowly work its way on with a little 'persuasion'

adding coolant;
er....mix coolant 50/50 with deionised water (not the limescale ridden rubbish i get in my taps) and poor into coolant tank until upto correct level.
run engine. hopefully the level will drop as engine warms up, fan comes on etc but it prob wont & your heater prob wont work either!!!! (its a crap plumbing system & you get air pockets everywhere.....)

run car with coolant cap on, use throttle to get it very warm on gauge, turn off engine, slowly (and carefully) remove coolant cap; you will see the coolant bubble as the pressure differences suck air out of the system. top up when cool.

Repeat, using throttle will force coolant around the system; you should be getting warm air from the vents now.....let engine warm, top up etc.

you should also be checking the thermostat is opening at 3/4 hot by placing hand on radiator (back one; front is aircon); be careful. the fan should also be working.

this will get it 90%.....test drive the car.....top up etc

keep a tub of mixed coolant in the boot for a month & check twice a week. it will be fine by the end of the month. garages can use a vaccum system to suck the coolant round / suck air out but with the puma its still crap! just carry some spare coolant for a while.

tada! other than being fiddly & getting air pockets its very simple

also a good time to replace the hcv; heater control valve seeing as youv got most of the coolant out to do this.....
Last edited by jacko on Sat Apr 11, 2009 11:00 am, edited 5 times in total.
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Post by red » Mon Dec 29, 2008 11:46 pm

Good interesting read. Be good to see completion.

Makes me wonder whether my Dads Mondeo has a faulty stat now.. it never gets up to tempt and the mpg isnt very good.
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Post by jacko » Tue Jan 06, 2009 9:29 pm

done
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Post by nicholas » Sun May 10, 2009 4:51 pm

That's just what the doctor ordered Cheers
Will attempt next week.
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Post by jacko » Sun May 10, 2009 7:28 pm

no probs, any questions fire away!
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Post by martinthrapston » Sun May 10, 2009 11:27 pm

great clear guide jacko and pics help alot!!!
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Post by jacko » Mon May 11, 2009 8:56 am

cheers
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Re: how to change the thermostat

Post by Gijs » Sun May 01, 2011 9:32 pm

Hello

great threat, worked for me, just to avoid to do the whole job again, when it didn't solve the overheating problem.


one advice .

remove the thermostate and put your finger in it and feel the propellor/rotor of the water pump
try to turn it arround and put a little pressure on the poulie of the waterpump.

if you still can turn arround the proppelor/rotor with your finger while the poulie stays in the same position
then your waterpump is knacked and a new thermostate won't solve your heating problem.

it will avoid a lot of frustration when you reeinstalled all parts and your engine is still getting
overheated.

How to change a waterpump can be found here

http://www.projectpuma.com/viewtopic.php?f=65&t=4330" onclick="window.open(this.href);return false;


best rgds
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Re: how to change the thermostat

Post by johnsbegood » Sat Oct 29, 2011 8:45 pm

Hi. My sister hcv blew out last night so had to sort the car today. I went to remove the thermostat to flush the coolant out the engine but couldn't see/get to the lower right 10mm bolt so just had to leave it in. I read in ur post u need to move the rad so u can actually see/get to that fourth bolt. Is there a guide to moving the rad?? Had a Haynes manual but it's limited to the fiesta model.
Cheers
Paul
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Re: how to change the thermostat

Post by ScubaSteve » Sat Oct 29, 2011 8:48 pm

dont need to remove rad you can get to it through drivers light hole if you remove it
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Re: how to change the thermostat

Post by johnsbegood » Sun Oct 30, 2011 12:13 pm

ScubaSteve wrote:dont need to remove rad you can get to it through drivers light hole if you remove it
Yeah I removed the headlight to get better access to the alternator bolts. Did them throbed moved the top two bolts and the lower left bolt on the thermostat housing but couldnt remove the lower right. I could just about get the socket and I little extension bar on it but when I came to put the ratchet on there was an air con pipe in the road????
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Re: how to change the thermostat

Post by ScubaSteve » Sun Oct 30, 2011 2:21 pm

mine doesnt have air con lol, maybe you need to get a shorter extension bar, or see if you can get the length using reducers etc
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Re: how to change the thermostat

Post by stereophoney » Fri Nov 01, 2013 7:04 pm

Thanks for the info, proved very helpful today. Had a leak since I bought the car, with the coolant going from maximum to minimum in a week, which was manageable. A couple of weeks ago it decided to dump a load of coolant and I had to top up 3l over a weekend, so the repair was a bit more urgent! There was no obvious leak when looking from above, but underneath there was a drip on the front edge of the sump, so after reading on here the most likely suspect was the thermostat housing.

Picked up a new housing and stat from Eurocarparts for £20 and set about changing it today. After many hours toil it's all back together and running fine, heater is scalding again! A few things I found might be of use to someone!

- I found the easiest way to take off the alternator belt was to put the spanner in place turning using my left hand and crouching in-front of the headlight, taking off the belt from the alternator pulley with my right. This also meant that the belt didn't need to be removed.

- The Fiesta Haynes manual isn't always accurate in regards to removing the alternator, as mine needed to be removed differently from the one in the book and that meant going out to buy an extra tool, an E8 star socket. I needed it as my alternator had 2 top bolts.

- I didn't need to lower the radiator.

- It would be a lot easier without Air-con!
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Re: how to change the thermostat

Post by neil19815 » Sun Mar 29, 2015 10:31 pm

Thank you for the guide. This has saved my bacon twice now. Hopefully I won't need to use this again.
Be carefull with the Europarts Thermostat. I replaced my original with one from Europarts and it has a high temperature point that has caused havoc with my Autosolo car.. Overheating... Have fitted a new one from a local parts company and it looks to be running fine.
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Re: how to change the thermostat

Post by trublustu » Sun Mar 29, 2015 11:03 pm

Here`s a quick tip..

In order to get the belt on and off with ease.
put a 13mm ring spanner on the nut in the middle of the tensioner and rotate to take the pressure off the belt then just slip it off the water pump.
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how to change the thermostat

Post by foggy » Wed Aug 02, 2017 12:13 am

Shame the pictures are no longer on this as they would give me the confidence to try this job myself.
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how to change the thermostat

Post by red » Wed Aug 02, 2017 9:01 am

It's not often such an old guide gets pulled up, the images were stored in our old gallery which was probably out of date 9 years ago.

I probably do still have a copy of the pictures but I'd need to see if I can correlate them to this thread because they are stored as with random strings as file names.
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how to change the thermostat

Post by red » Wed Aug 02, 2017 9:40 am

How's that for service? The pics are restored.
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how to change the thermostat

Post by lusid666 » Wed Aug 02, 2017 12:30 pm

I changed mine through the headlight hole. Tight? I should have been a gynecologist lol
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