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I recently made a long trip with my 24V; engine temperature fluctuated between 80°C and just over 60°C when the outdoor temperature dropped. I can conclude that the thermostat is faulty?

Someone told me that the engine should always work close to 90°C.
 

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I recently made a long trip with my 24V; engine temperature fluctuated between 80°C and just over 60°C when the outdoor temperature dropped. I can conclude that the thermostat is faulty?

Someone told me that the engine should always work close to 90°C.
Sounds like thermostat stuck open and not fully closing.

It should start to open at about 87C and engine should operate at about 90-98C for best efficiency.
 

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Cooktop testing of Alfa 164 thermostat

I tested mine today on stove with turkey and beef thermometer for temp guide.

I got it to start to open at 87C/188F and fully open at 194F. Fully closes about 180F/83C.

This is neoprene poppet style rated at 87C/188.6F opening.

The stainless steel poppet one opens at 83C/181.4F
 

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Sounds like you got what you needed, but when has that ever stopped me?

As another data point.. I had a stuck-open thermo. on my '93 L. I noticed that during city driving the gauge indicated a normal fluctuating temp. range, but.. once on the freeway, the motor started running substantially (maybe 20-30 degs.) cooler than was typical.

When the old one came out.. sure enough.. it was not closing/sealing, even at room temp. The gap was not large (~ 1/8 - 1/16") but apparently enough.

The replacement thermo. got everything right back to normal.
 

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And for my two cents - never be tempted to modify a slightly-open thermostat by drilling the hole deeper in the housing. One day, it may fail to open, as mine did.

Core of 156 V6 thermostat fits in 164's housing - this helped me find a replacement locally.

-Alex
 

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Discussion Starter #7
I know many good people here (including good mechanics) who think that keeping the temperature too low is a great advantage.
 

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Why do they think so?
 

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I know many good people here (including good mechanics) who think that keeping the temperature too low is a great advantage.
Many mechanics do not have a good handle on engineering.
Charles
 

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Another thing to add to my list. Mine runs too cold. 60/80º during most of the time. The heating takes forever to blow hot air.

Well, I'll just start hunting for a new thermostat. I never did disassembled a thermostat though. Time to learn.
 

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Another thing to add to my list. Mine runs too cold. 60/80º during most of the time. The heating takes forever to blow hot air.

Well, I'll just start hunting for a new thermostat. I never did disassembled a thermostat though. Time to learn.
 

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Worst part of the thermostat job is when one of the three long 11mm head/7mm thread bolts shears. Then the job suddenly becomes much more complex as you'll need to remove the two short hoses to the cylinder head (prone to leaks), unbolt the top of the water pump, grind off/drill out the sheared bolt, and do a thread repair. This has happened to me twice. For this reason, it's probably a good idea to have three replacement bolts on hand (ordered from a specialist; usually not available at a local bolt shop) and replace them if showing signs of corrosion. Obviously, go carefully with removal - twist a little each way, backing out a little at a time... The problem is caused by the length of the bolts; they go through the 'water jacket' of the housing sandwich, so tend to corrode into the bottom part (hard to get penetrating oil in there).

As for running too cool, in a hot climate it is sometimes nice to have the extra 'safety margin' for cooling attainable if the engine is running too cool most of the time; then it takes a little bit longer to warm up to 'hot' in traffic, etc. But realistically, if the radiator is good, there is no advantage (after all, more heat is lost the hotter the radiator gets; that's thermodynamics). Also, the temp gauge on 164s seems frequently inaccurate. I had a faulty sender that always over-read (over 100 degrees) after it was overheated one time. I changed the sender and I'm happy now that the gauge sits in the middle (90 degrees).

Remember also not to remove the thermostat completely in this bypass design; otherwise, the engine will take even longer to warm up because the coolant will not be diverted back to the water pump (bypass passage) properly, and conversely, the coolant may take a shortcut through the bypass passage when hot (instead of going through the radiator). That is why the thermostat has a small spring-loaded disc on its base, which closes off the bypass passage. Chances of mechanics understanding this part... sometimes quite low. It's knowledge that varies for each engine design.

As I mentioned, 156 V6 thermostats (not Twinspark) have a core that fits the 164 housing, all dimensions correct. Don't know about the situation in Brazil but if it's like NZ, 156 replacement parts are now much more readily available than 164 parts. I even threw away the brand-new 156 housing (elbow). Might live to regret that.

Just now I grabbed a "164 Super" thermostat in a private sale online, new for NZ$35 (US$26). This will be for a 24V 164, I don't know if that is the same as for a 12V (it looks the same?) but again, the core appears to twist-and-remove so I'm sure it will come in useful some day.

-Alex
 
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