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Thermostat Replacement

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How hard is it to change the thermostat on our little cars, im running a stock motor. Ive done them before on Handas, toyewtas, etc....

Just wondering if there is anything special, precautions, or easier steps rather then me finding out the hard way. TYIA


recent issues ive tackled on my car :

replaced the carrier bearing (center bearing)

replaced the pistons on the rear drums

replaced the rear boots (clear ones non CV bearing)


next up :

replace rear drums

replace thermostat

replace serpentine belt

possibly water pump

rewire the euro signals to make the city light work in the euro H4's


Edited by jayamasaki

1968 BMW 1600 Chmnx White

1976 2002 Parts car

2003 f150

60% of the time, it works every time!

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Pretty easy job--and a good opportunity to replace any suspicious-looking hoses (especially check the little short one between the heater valve and the heater core--I discovered to my horror that mine was original after 26 years and was hard as a rock.  I had to saw it off!)  You can also change antifreeze at the same time if yours is more than a couple of years old. 


1.  Drain radiator:  have a BIG catch basin because the antifreeze will run all over the place since there's no drain cock, only a bolt.  You can try wedging a plastic funnel between the nose and the swaybar--that should catch most of it.  And this might be a good time to have a radiator shop check yours for leaks/weak spots, and solder in a proper drain cock to replace the bolt.


2.  Drain block:  the drain is a 17mm bolt inconveniently placed under the exhaust manitold.  Again, use a funnel and hose to catch the coolant...and see if you can find a drain cock that will screw into the hole; it'll make the job MUCH easier the next time. 


3. Once the coolant is drained, simply undo the three hose clamps that hold the 'stat in place (if you haven't discovered it, the 'stat is on the engine's right side, between the lower radiator hose and the block.) pull the old one out and install the new one.  A little silicone grease or "personal lubricant" will make the hose slip on much easier.  And make sure you install the 'stat correctly, not upside down!  It can be done!


4.  Replace the drain plugs, open the heater valve to full hot and refill with coolant.  Start the engine with the cap off, and continue to add coolant as the 'stat opens.  Sometimes burping air pockets out of a 2002 is a long process, so you may have to add coolant several times and drive it a little to get the system full of coolant and purged of air.  Final coolant level cold should be an inch or so below the radiator cap neck.  Any excess will vent onto the ground so no sense in overfilling. 


Have fun, and clean up spills as most antifreeze is toxic to animals.



'69 Nevada sunroof-Wolfgang-bought new
'73 Sahara sunroof-Ludwig-since '78
'91 Brillantrot 318is sunroof-Georg Friederich 
Fiat Topolini (Benito & Luigi), Renault 4CVs (Anatole, Lucky Pierre, Brigette) & Kermit, the Bugeye Sprite

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Couple of additional tips:  If you can park the car on an upgrade (or jack the front end up) it seems to help when refilling the coolant, and, a tip from someone on this board that I took advantage of, is to go to Home Depot or Lowe's and get a fairly cheap concrete mixing pan to catch the coolant as you drain the system. 


My Home Depot had two sizes and the smaller one works fine.  It's considerably larger in footprint than an oil drain pan so you catch all the coolant with little or no spillage.  Cost was a little less than $10 if I remember correctly.


Bob Napier

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M10 thermostats are tricky little devices. Even watching them actuate when placed in a pot of boiling water, you have to look at the diagram in the manual to see if it is working properly.  Change all the hoses if you don't know how old they are (as Mike Self pointed out).



Coolant change >>


I just changed the coolant on the tii last weekend.  My radiator does not have a drainbolt, so I slowly pulled the bottom radiator hose with a large plastic bin below the radiator and a smaller bin at the right frame rail section to catch the inevitable coolant that runs down into that spot.


The engine block drain bolt takes a 19mm socket. I was surprised mine was not really that tight.  Be prepared for a giant gushing of coolant. Make sure to buy a new sealing ring before starting this job.  It is not the same one as used on the oil pan and rear diff bolts.


After re-filling the radiator, I squeezed the hose between the t-stat and coolant manifold (branch divider) to release air bubbles, then started the engine to check for leaks.  I had to do more burping because I wasn't getting hot air out the heater (check both sides of the heater core at the hoses and squeeze one or both of them to help remove the air pockets).


Make sure to rinse off the parts that got sprayed with coolant.  I have some belt squeaking which I hope will go away.

Jim Gerock


Riviera 69 2002 built 5/30/69 "Oscar"

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Make sure you mark which direction is up on the thermostat so you can put the new one in the same orientation.

I guess you could install it upside-down, but the angled stub points to the coolant branch manifold


Jim Gerock


Riviera 69 2002 built 5/30/69 "Oscar"

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the most important partis not traping air, and being sure all air

is bled out during the refilling process.


fill by mixing HOT HOT water with your antifreeze (45%antifreeze/55%agua)

and leave the top hose to the thermostat off. Fill thru that disconnected

hose slowly feeling for that hot mix in the other hoses and radiator.

Fill as much as you can before reattaching that upper thermostat hose.

Switch the heater hot water valve to hot.

Start the engine and idle - vary the idle high/low abit to promote

coolent circulation - watching the temp gauge. Shut off if the gauge

climbs to near RED and let it sit for 15+ minutes to cool.

Restart after adding coolent if needed and repeat this process

untill full, and full heat is felt. Finally after the temp gauge has

stabilized in 'normal' range,shut off and let cool over night or 6

hours. Top up radiator  but leave about 2" below the cap fitting.

You need to leave room for expansion.


good luck



Edited by c.d.iesel

'86 R65 650cc #6128390 22,000m
'64 R27 250cc #383851 18,000m
'11 FORD Transit #T058971 28,000m "Truckette"
'13 500 ABARTH #DT600282 6,666m "TAZIO"

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thanks for all the suggestions guys. I just replaced the belt, no more squealing like pig. Due to the Beemer fest this weekend, I will not be changing my thermostat on Sat. Maybe Sun...


again, thank you !

1968 BMW 1600 Chmnx White

1976 2002 Parts car

2003 f150

60% of the time, it works every time!

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