Install report: SPD 170 deg thermostat

[Aonarch]

I'm old and remember people removing the stat altogether, I might have done it a time or two myself. Later I read that removing it can also cause overheating because the coolant flowed too fast and didn't stay in the radiator long enough to cool off.

Depending on ambient temperature, engine load, those sorts of things, that it doesn't matter much what temp your thermostat is too. Hypothetically, say the coolest your engine is going to run is 195 then it won't matter if you run a 170, 180, or 190 thermostat.

At constantly cooler temps your internal clearances are wider. One reason why marinized automobile engines don't last long in boats is they run in a high load, high throttle, low temp environment. They either run very low-temp stats or no stat because you don't want the water from the lake, river, or ocean to boil and leave a bunch of crud in the cooling passages. Kills the motors though and you can't knock the heads off the block with a sledgehammer.

This is an important part to explain, so let me expand upon this excellent post.

The 170F rating simply means that the thermostat opens once the coolant hits 170F. Engines do not like to be too cold. Ford has obviously decided that the OEM temperature is optimum for the engines operating temperature. So the designed that thermostat to ensure it gets up to temperature as fast as it can and then doesn't drop below it.

So as Phil said, say you are starting your Ranger up on a cold winter day and idling in traffic, it might never get above 170F, since coolant will start flowing into the engine at 170F. Well clearly the engineers want a higher operating temperature than that.

Sludge has already been called out, but that is a big one, ESPECIALLY if you take short trips. Your oil temperature will be lower than desired, which means water and other junk won't burn off.

In some racing series they actually pipe operating temperature coolant through the engine before starting it. That is because of metal expansion, combustion, and for a street car the catalytic converter.

I'd want to know why specifically you switched to a lower temp thermostat. What problem are you trying to solve?

Then lastly, what effect does this have on the other cooling system components? The radiator, the fans, the water pump, etc.

Can they handle a 170F Tstat?

Simply put, a thermostats job is to keep the engine warm, not cold.

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[Frenchy]

This is an important part to explain, so let me expand upon this excellent post.

The 170F rating simply means that the thermostat opens once the coolant hits 170F. Engines do not like to be too cold. Ford has obviously decided that the OEM temperature is optimum for the engines operating temperature. So the designed that thermostat to ensure it gets up to temperature as fast as it can and then doesn't drop below it.

So as Phil said, say you are starting your Ranger up on a cold winter day and idling in traffic, it might never get above 170F, since coolant will start flowing into the engine at 170F. Well clearly the engineers want a higher operating temperature than that.

Sludge has already been called out, but that is a big one, ESPECIALLY if you take short trips. Your oil temperature will be lower than desired, which means water and other junk won't burn off.

In some racing series they actually pipe operating temperature coolant through the engine before starting it. That is because of metal expansion, combustion, and for a street car the catalytic converter.

I'd want to know why specifically you switched to a lower temp thermostat. What problem are you trying to solve?

Then lastly, what effect does this have on the other cooling system components? The radiator, the fans, the water pump, etc.

Can they handle a 170F Tstat?

Simply put, a thermostats job is to keep the engine warm, not cold.

I will agree with you on quite a bit of this. In my opinion I can say the transmission can get warm in certain conditions(but still do fine). If I were to do anything to help control said temperature I would do one of two things, install a more efficient trans cooler or a pan with cooling fins. What would be the effect? Simple, the transmission would have a tougher time getting close to 250°F(wich mine.got close plenty of times OffRoad). As cor the envine cooling side I would change the radiator to a full aluminium and change the intercooler mainly for hogh load applications like towing. The same affect would happen for the engine and it would cool more effectively. Even then the Ranger does well for the most part in temperature management.

I definitely feel the OP should have taken a different approach on this all together

 

[Mokume]

This is an important part to explain, so let me expand upon this excellent post.

The 170F rating simply means that the thermostat opens once the coolant hits 170F. Engines do not like to be too cold. Ford has obviously decided that the OEM temperature is optimum for the engines operating temperature. So the designed that thermostat to ensure it gets up to temperature as fast as it can and then doesn't drop below it.

So as Phil said, say you are starting your Ranger up on a cold winter day and idling in traffic, it might never get above 170F, since coolant will start flowing into the engine at 170F. Well clearly the engineers want a higher operating temperature than that.

Sludge has already been called out, but that is a big one, ESPECIALLY if you take short trips. Your oil temperature will be lower than desired, which means water and other junk won't burn off.

In some racing series they actually pipe operating temperature coolant through the engine before starting it. That is because of metal expansion, combustion, and for a street car the catalytic converter.

I'd want to know why specifically you switched to a lower temp thermostat. What problem are you trying to solve?

Then lastly, what effect does this have on the other cooling system components? The radiator, the fans, the water pump, etc.

Can they handle a 170F Tstat?

Simply put, a thermostats job is to keep the engine warm, not cold.

Well written and very accurate response!

Sludge buildup is a particular issue with urban Honolulu driving, some motorist have such short commutes that the engine management system may never go into closed loop operation.

This is one of the reasons (of several) why engine designers want to get the motor up to normal operating temperature pronto, they also want those cats to light up asap as well.

I've disassembled engines in the past with excessive sludge buildup, it was not a pretty sight.
Some of the owners of these vehicles used a particular "fast lube" service which is known to exclusively use a particular brand of motor oil, I won't mention the brand. I'll only use this brand if I should find myself stranded in the Mohave Desert and needing motor oil.

Cars driven in urban Honolulu have a rough life, given the amount of time they find themselves in stop and go traffic, I daresay a vehicle which has travelled 100K miles here is akin to one driven 300K on the mainland...

 

[Porpoise Hork]

Well at least it's not like doing it on an audi 6 cyl . As I do shorter trips now <10 miles, I want the engine to quickly reach operating temp to burn off any contaniments, esp fuel.

Seeing this confirms that I do not in any way miss working on my VW...

 

[dtech]

Seeing this confirms that I do not in any way miss working on my VW...

Good catch because the car in the pic is actually a VW with the V6 and apparently both Audi's and VWs were designed to make the front end easy to remove for service access., and replacing the thermostat was recommended when the t belts were changed.. My friend with the Audi was plagued with electrical gremlins, just like vw.

 

[Mokume]

Good catch because the car in the pic is actually a VW with the V6 and apparently both Audi's and VWs were designed to make the front end easy to remove for service access., and replacing the thermostat was recommended when the t belts were changed.. My friend with the Audi was plagued with electrical gremlins, just like vw.

It's thoughtful that VW made the front of the car easily removeable, it makes the front on the engine very easy to work on.
However, having to remove the timing belt to replace the t/stat is absurd. Is the water pump driven by the timing belt? If so, it would behoove the owner not to replace it with a reputable NEW pump.
Is the pale blue thing a vacuum reservoir? I remember peering into the engine compartment of my Mom's then new '67 Mercury Colony Park with my Dad and seeing what resembled a pineapple juice can painted black attached to one of the fender liners.
It was sure an un-elegant version of a vacuum reservoir, functional but ugly...

 

[Blmpkn]

Ass backwards German engineering is Germanys way at getting back at the rest of the world for kicking their dirty no fun having asses twice about 100 years ago.

 

[Mokume]

Ass backwards German engineering is Germanys way at getting back at the rest of the world for kicking their dirty no fun having asses twice about 100 years ago.

Lol...so true
My Dad's vintage 420 SEL's HVAC controls began as electrically operated, turn to vacuum, then back to electrical...go figure

 

[MXGOLF]

Wow thanks for all the input about the thermostat. I believe I will just change the plugs that Torrie gave me and leave the thermostat alone. I do want to keep my Ranger long term and don't want to mess with any of the critical systems such as coolant. I am still used to the older cars and trucks where I could do everything and never have to take them to a expensive mechanic and really miss that. Although I am getting older where I can't do that stuff even if I wanted LOL.

Thanks,

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