Thermostat mod
11-25-02, 03:09 AM
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Thermostat mod
hokay, actually learned this one for the winter beater (Daytona) but seems it might help those in colder climates driving ReXes year round...
One of the achilles heals of the Chryco 2.2 litre engine is the head has a tendancy to slightly warp or blow a gasket (for an econocar they're actually not bad engines, but considering for close to a decade they're pretty much the only engine Chrysler made, I'd HOPE they got it right!)
Anywho, one of the main reasons for this is thermal shock. You get in the car and start it, the thermostat holds the coolant in the engine until it heats up to operating temperature, then opens to allow cool coolant from the rad in and heated coolant out. However, this means right after you get your engine nice and toasty it gets doused with cold coolant (like pouring cold water onto hot metal, hence thermal shock)
A solution to this is to drill a 1/16th hole through the flange of the thermostat that allows a tiny jet of coolant to circulate. This allows a bit of coolant to seep into the radiator, warming it above atmospheric temperature so when the thermostat opens it isn't stone-cold coolant suddenly surging in. 1/8th hole would allow too much coolant through and it'll take far longer to reach Op Temp, and even then in 2.2s it prevents it from reaching the optimum 180 degrees (hovers around 160 instead)
Although the bread-slice design of our beloved 12As and 13Bs aren't as succeptible to the warping that the cylinder head on the 2.2 is, it would seem that introducing semi-warm coolant to a hot engine would be preferable to cold coolant on the same hot metal, if only to minimize a momentary cooling of the side housings. Our engines are fairly dimensionably stable, from what I've been told, but the flatter heating & cooling curves are, the better.
One of the achilles heals of the Chryco 2.2 litre engine is the head has a tendancy to slightly warp or blow a gasket (for an econocar they're actually not bad engines, but considering for close to a decade they're pretty much the only engine Chrysler made, I'd HOPE they got it right!)
Anywho, one of the main reasons for this is thermal shock. You get in the car and start it, the thermostat holds the coolant in the engine until it heats up to operating temperature, then opens to allow cool coolant from the rad in and heated coolant out. However, this means right after you get your engine nice and toasty it gets doused with cold coolant (like pouring cold water onto hot metal, hence thermal shock)
A solution to this is to drill a 1/16th hole through the flange of the thermostat that allows a tiny jet of coolant to circulate. This allows a bit of coolant to seep into the radiator, warming it above atmospheric temperature so when the thermostat opens it isn't stone-cold coolant suddenly surging in. 1/8th hole would allow too much coolant through and it'll take far longer to reach Op Temp, and even then in 2.2s it prevents it from reaching the optimum 180 degrees (hovers around 160 instead)
Although the bread-slice design of our beloved 12As and 13Bs aren't as succeptible to the warping that the cylinder head on the 2.2 is, it would seem that introducing semi-warm coolant to a hot engine would be preferable to cold coolant on the same hot metal, if only to minimize a momentary cooling of the side housings. Our engines are fairly dimensionably stable, from what I've been told, but the flatter heating & cooling curves are, the better.
11-25-02, 06:14 AM
#3
I read your email
Interesting, I always wondered what that hole was for. The Mazda thermostat has such a hole in it. They instruct you to position the thermostat so the hole is at the top.
11-25-02, 12:01 PM
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bmw used 2 thermostats to try and fix this problem in the 70s?
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11-25-02, 12:37 PM
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Yeah, the one Mazda (and ford) uses with the ball bearing is for air. I just changed the one on my Explorer, which is the same as the Mazda Navajo. The book says its to relieve air pressure.
11-25-02, 01:45 PM
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Yeah, I thought the one in the Mazda 'stat was to allow air to bubble out, but wasn't sure of the circumstances under which it opened - whereas this simple mod is an 'always on' temperature equalizer (the key being 1/16th" but no larger for the hole)
Again it isn't as critical with our engines (even though rotaries are less thermally efficient) as it is to prevent cylinder head gaskets from going kerblewy in boingers, but shock is shock and who wants to fatigue engine metal if you can avoid it?
Again it isn't as critical with our engines (even though rotaries are less thermally efficient) as it is to prevent cylinder head gaskets from going kerblewy in boingers, but shock is shock and who wants to fatigue engine metal if you can avoid it?
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