170 Thermostat= No heat?

saint777

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Hey guys just popped a new engine in my 95 town car and I switched to a 170 degree thermostat to replace the 195 that was in there originally. Now I don't have any heat, could thus be the culprit? Also never had a check engine light on before the motor swap, maybe I missed a wire or something but I don't think so, would the light come on due to this as well?..
 

Robot

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Do your vents not blow air on the heat setting? Are you using AUTO setting?
 

TourDeForce

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Hey guys just popped a new engine in my 95 town car and I switched to a 170 degree thermostat to replace the 195... never had a check engine light on before the motor swap, maybe I missed a wire or something but I don't think so, would the light come on due to this as well?..

If your 1995 is an OBD I system, so the thermostat should not trigger the CEL. OBD II cars will trigger a CEL if the thermostat is too cool because (tree hugger reasons). A 180 should work fine.

Take your car to an auotzone store and ask them to get and WRITE DOWN the exact codes they report. Look them up on the internet and one of them may indicate a thermostat stuck open, or some such engine temp control malfunction if the thermostat is at fault.
 

TourDeForce

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Why would you use a 170, especially in Boston. Gas mileage may drop and sludge increase.

Fuel mileage should go up slightly, and since engine temps are lower you get less sludge because the oil breaks down as a result of higher temps, not lower.

Back in the day engines ran pretty cool. 160 thermostats were pretty common. Emission standards required a cleaner burn and part of the formula to achieve this was higher engine temps. Trouble with that is you get pre-ignition - especially since we don't put lead in gasoline any more. To combat pre-ignition (pinging and knocking) manufacturers had to pull timing which reduces efficiency and power. So, higher temp thermostats are nothing more than built in heat-soak.

With the introduction of modern engine management (OBD II in this case) a cold engine will run in closed loop off of internal tables, but once warmed to normal operating temperature of 140 or so, they enter the open loop mode which gathers info from various sensors to refine the mix and timing for optimal emissions and mileage. As the engine gets hotter than about 160 the computer pulls timing to prevent pre-ignition. Hotter it gets, more timing is pulled = Bad for performance and efficiency. Here's a table from the VWVortex.com website to summarize. It's a bit low res, but you get the idea that at any given RPM timing is taken away as temperature rises:

http://i36.photobucket.com/albums/e5/TooLFan46n2/Eurodyne Maestro Reference Thread/Igntion and Cam Timing//timing_corr_air_temp.jpg
 
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atikovi

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Fuel mileage should go up slightly, and since engine temps are lower you get less sludge because the oil breaks down as a result of higher temps, not lower.

Engine is designed for a 195 thermostat. With a 170 the computer thinks it hasn't warmed up and will richen the mixture and raise the idle. Both will lower gas mileage. And sludge forms when condensation in the oil doesn't burn off if it doesn't get hot enough. For oil to break down from heat, it would have to get a lot hotter than a 195 degree thermostat would allow.
 

TourDeForce

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Engine is designed for a 195 thermostat. With a 170 the computer thinks it hasn't warmed up and will richen the mixture and raise the idle.

Wrong. The normal operating temp starts at just over 140 when the computer goes into open loop. No matter what thermostat you put in the car, the engine warms up to normal operating temperatures just as fast, so you're not running rich at 170. In fact, you actually run leaner at 170 vs. 195 because the computer doesn't have to pull as much timing. Check the table I linked.

The magic 195 is ideal for emission control purposes, but far from ideal for an efficient running engine. Less energy wasted generating heat = more energy being put to use to move the car.
 

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