Thermostat Change on a 420a



Introduction: Thermostat Change on a 420a

A not tooo detailed instrutcable on how to change the thermostat on the 420a Engine... which is an Eclipse, avenger or similar engine from the DSM era.

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Step 1: Hose Out!!

OK!!! first step.... LET THE ENGINE COOL DOWN!!!... most important step ever... then take the cap off... take the radiator house out and the coolant reservoir one... we want the housing by itself. Sit and contemplate how much c*** is on there

Step 2: Unscrewing

Now... to the sides of the thermostat housing there are gonna be a coupl of bolts.... i suggest you use a wrench for this... 13mm or 1/2 would do... take them of and gently clean them out of rust... cuz i assure you... THERE's gonna be rust

Step 3: The Agony and the Rust

Years of water or antifreeze running through metal.... what can we expect? rust, specially if you have never changed your thermostat..... lookie here... this is my old one.... we take the housing off (if youre not able to after the bolts, wiggle it or lightly hit it with a rubber mallet) and proceed to change the actual thermostat here.... make sure you clean both sides of the housing... or else youre gonna have leaks EVERYWHERE when putting it up back up again.

Step 4: Teh HEAT!!!!

Allright... here is the comparison of both thermostats.... the one on the left is the new one (no? seriously??) and the one on the right is the old one.... By default... you should get a 190f one... (a 195f would be ok...) that means that your thermostat is gonna let water into the engine at that temperature... it opens up and lets the flow in. In most cases, tunners or people who actually drives them hard like to use 180F failsafe thermostat... opens up at a lower temp to cool, and it if gets broken it stays open... one disadvantage to this.. is that if you live somewhere cold... your car will take forever or will NEVER warm up... it depends on where you live and the normal temperature.

Step 5: Out With the OLD, in With the NEW

Here's your new thermostat installed.... lightly cover its perimeter with RTV Sillicone (as if it was a gasket maker) and use that to stick it in its place... the wiggle valve (i have NOOO clue as to what it is for) must be on top.

Step 6: SOO Almost Done!

OK.... both sides of the housing must sandwich a bit of sillicone between them... let it dry a bit for about 5 mins then put them together... afterwards we're gonna put more all around it, to prevent any kind of leaks on it... According to the sillicone instructions it takes about 10 to 20 mins to dry... i left it for an hour before turning the car back on again.... Remember..... it takes about 1 day to COMPLETELY cure up... so.. no driving hard and stuff.

Step 7: DONE!!!

Ok... were done... put the radiator hose back on it... also the reservoir and fill both if you actually drained them or if you made a mess... wait the agreed times on the sillicone for it to cure and turn the car back on afterwards and let it idle just to make sure the new thermostat is working fine.

Step 8: Last Notes and Disclaimer

OK! well.. this instrucatble is just a lil bit of help to those who want to change the thermostat on their DSM cars..... PLEASE do not blame me for something utterly stupid such as: "i burnt my hand cuz of you!!!" "i opened the radiator cap and burnt my face!!!" or something of the like. REMEMBER, working with engines requires a LOT of common sense, and in this case a new thermostat, Sillicone and a wrench.
If youre unsure of something here, please go out and buy a haynes book.... not expensive...
Remember i do not take responsability as to if you hurt yourself or your engine... these are just guidelines and im not forcing you to do something, in the end you decide if you do it or not....
Thank you for reading and happy driving...

Serge RS

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    4 Discussions


    8 years ago on Introduction

    i went to napa and they gave me a 117 thermostat for 180degree F or 82 degree C.... and it doesnt look the same .. would it still fit?


    Reply 12 years ago on Introduction

    Thnk you =) just to help people out here....