83 Gsl Running Hot
08-23-2005, 11:42 AM
#1
Junior Member
Thread Starter
Join Date: May 2005
Posts: 7
Well, I'm not sure what is normal for this car. Driving easy on a summer day the gauge sits about 1/2 way and all is good. Without the A/C running, on a hot summer day (95-100 degrees), if I have to much fun on the back road home the temp gauge goes to about 3./4 gauge, which makes me, and the engine, uncomfortable. It will cool down some if I take it easy, but will not go back to "normal" while I am driving. With the A/C on, 95-100 degree day, driving normal will push the gauge past 3/4 in about ten miles and I usually will not push it past that. I'm not sure if it will continue to overheat if I keep driving, I'm not that brave. Again, turning off the A/C will lower the temp, but not to normal. This car was sitting for 2 1/2 years before I bought and reserected it in June. Just got the A/C working last week. Thermostat? Clogged radiator? Need an auxiliary fan? Water pump? Where should I start?
01-08-2006, 01:12 AM
#4
Senior Member
Join Date: Dec 2005
Location: Oregon
Posts: 407
The stock mazda gauge sucks for one.. yeah you should try to flush her out mabie replace the thermostat. HEAT is one of the bigest killers of the rotary an A/C sometimes = heat... You can always try a electric cooling fan plus it will free up some ponys at high RPM's... 
01-08-2006, 12:01 PM
#5
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Join Date: May 2002
Location: California
Posts: 22,465
Originally Posted by RE_TurboFB' post='792794' date='Jan 7 2006, 11:12 PM
The stock mazda gauge sucks for one.. yeah you should try to flush her out mabie replace the thermostat. HEAT is one of the bigest killers of the rotary an A/C sometimes = heat... You can always try a electric cooling fan plus it will free up some ponys at high RPM's...
the stock mazda guage is as good any any other guage, try it, mine reads within 1degree of the greddy.
start with a thermostat, but it might need a radiator too, or get it rodded out
01-14-2006, 11:46 PM
#6
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Join Date: Dec 2005
Location: Oregon
Posts: 407
[quote name='j9fd3s' date='Jan 8 2006, 10:01 AM' post='792822']
the stock mazda guage is as good any any other guage, try it, mine reads within 1degree of the greddy.
Mine was real old (22 years old) It was off 8 degrees off from the cheap summit racing guage I bought..
Could the summit gauge be off..?!?!
the stock mazda guage is as good any any other guage, try it, mine reads within 1degree of the greddy.
Mine was real old (22 years old) It was off 8 degrees off from the cheap summit racing guage I bought..
Could the summit gauge be off..?!?!
01-15-2006, 11:19 PM
#7
Senior Member
Join Date: May 2005
Location: Choctaw, OK
Posts: 178
The stock gauges are pot-luck when it comes to accuracy. Some are pretty close, a lot aren't.
1) Clean all the leaves and gunk out of the front of your radiator. Then take your fan shroud off and use a water hose to clean out all the crap.
2) Make sure all your hoses are in good shape. If one of your hoses has a cut on the inside, it can make a flap that severly limits coolant flow.
3) If your fan shroud is missing, get one. A missing fan shroud means half your radiator is going unused.
4) Check your coolant with a hydrometer. If your coolant isn't at least 50% water, then it isn't cooling properly. Glycol is there to keep the system from rusting out or freezing, so make sure you have no less than 40%. The easiest way to get a good mix is by using a hydrometer. When five out of the six ***** are floating you have enough glycol to keep it from freezing. If the sixth ball floats you have too much glycol and your engine can't get rid of the heat.
5) Make sure your radiator is full of coolant and there are no air pockets. This really isn't hard to do on an RX-7 because the radiator cap sits above the rest of the cooling system. Just fill 'er up.
6) If you regularly run over 6000 rpm, or have a hoss engine and hit 9000 rpm on occasion, invest in a reduced diameter eccentric pulley.
At high rpm your water pump moves coolant too fast, reducing pressure on the inlet side of the pump. With a reduction in pressure comes a reduction in boiling point. If the coolant's boiling point drops below its temperature then the coolant boils. The water pump is a good fluid pump, but a terrible vapor pump. Cavitation is what happens when the fluid in the pump is replaced by vapor. It means your water pump becomes ineffective until either (a) the pressure returns and raises the boiling point, forcing the coolant back into a liquid state, or (b) the coolant temperature drops and it returns to liquid on its own. This all happens in a few seconds, but if repeated through several corners, your coolant temperature can raise faster than your radiator can catch up. It also means you can get localized hot spots in your engine which can lead to the dreaded leak-of-death or hot-spots on your side housings.
A reduced diameter eccentric pulley turns your water pump slower, which means the water pump can't move the coolant fast enough to cause the pressure drop that leads to cavitation. Your water pump won't move as much coolant at idle, but it shouldn't be a problem unless you have a pretty radical engine.
7) If you have a beehive oil cooler (coolant-to-oil oil cooler), consider swapping to an earlier or later air-to-oil oil cooler. You oil cooler does a significant amount of engine cooling. If you have any porting, you probably need an air-to-oil cooler.
8) If your setup is pretty hot, consider having your radiator recored.
9) Consider an electric fan. I wouldn't use anything that moves less than 2000 cfm.
The engine in my '83 GSL is a half-bridgeported 12A with a 2nd gen aluminum water pump housing and a 2nd gen cast iron water pump. I'm running an '82 radiator (short radiator) recored with a 3-row core and an '82 air-to-oil oil cooler. My engine regularly hits 9000 rpm so I also have a reduced diameter eccentric pulley. I have a Flex-A-Lite Black Magic fan mounted in a stock shroud. This summer at SCCA events it routinely idled at 800 rpm for long periods of time without showing any signs of overheating.
1) Clean all the leaves and gunk out of the front of your radiator. Then take your fan shroud off and use a water hose to clean out all the crap.
2) Make sure all your hoses are in good shape. If one of your hoses has a cut on the inside, it can make a flap that severly limits coolant flow.
3) If your fan shroud is missing, get one. A missing fan shroud means half your radiator is going unused.
4) Check your coolant with a hydrometer. If your coolant isn't at least 50% water, then it isn't cooling properly. Glycol is there to keep the system from rusting out or freezing, so make sure you have no less than 40%. The easiest way to get a good mix is by using a hydrometer. When five out of the six ***** are floating you have enough glycol to keep it from freezing. If the sixth ball floats you have too much glycol and your engine can't get rid of the heat.
5) Make sure your radiator is full of coolant and there are no air pockets. This really isn't hard to do on an RX-7 because the radiator cap sits above the rest of the cooling system. Just fill 'er up.
6) If you regularly run over 6000 rpm, or have a hoss engine and hit 9000 rpm on occasion, invest in a reduced diameter eccentric pulley.
At high rpm your water pump moves coolant too fast, reducing pressure on the inlet side of the pump. With a reduction in pressure comes a reduction in boiling point. If the coolant's boiling point drops below its temperature then the coolant boils. The water pump is a good fluid pump, but a terrible vapor pump. Cavitation is what happens when the fluid in the pump is replaced by vapor. It means your water pump becomes ineffective until either (a) the pressure returns and raises the boiling point, forcing the coolant back into a liquid state, or (b) the coolant temperature drops and it returns to liquid on its own. This all happens in a few seconds, but if repeated through several corners, your coolant temperature can raise faster than your radiator can catch up. It also means you can get localized hot spots in your engine which can lead to the dreaded leak-of-death or hot-spots on your side housings.
A reduced diameter eccentric pulley turns your water pump slower, which means the water pump can't move the coolant fast enough to cause the pressure drop that leads to cavitation. Your water pump won't move as much coolant at idle, but it shouldn't be a problem unless you have a pretty radical engine.
7) If you have a beehive oil cooler (coolant-to-oil oil cooler), consider swapping to an earlier or later air-to-oil oil cooler. You oil cooler does a significant amount of engine cooling. If you have any porting, you probably need an air-to-oil cooler.
8) If your setup is pretty hot, consider having your radiator recored.
9) Consider an electric fan. I wouldn't use anything that moves less than 2000 cfm.
The engine in my '83 GSL is a half-bridgeported 12A with a 2nd gen aluminum water pump housing and a 2nd gen cast iron water pump. I'm running an '82 radiator (short radiator) recored with a 3-row core and an '82 air-to-oil oil cooler. My engine regularly hits 9000 rpm so I also have a reduced diameter eccentric pulley. I have a Flex-A-Lite Black Magic fan mounted in a stock shroud. This summer at SCCA events it routinely idled at 800 rpm for long periods of time without showing any signs of overheating.
02-07-2006, 10:01 PM
#8
Junior Member
Join Date: Feb 2006
Location: Puyallup Wa
Posts: 11
Excellent commentary by BeaterRX7 only thing I might add is check your clutch fan. It will be stiff when the car is cold but once it warms up it will free up some. It will never turn as fast as the RPMs but I you (or previous owner) have wound it up a lot. The clutch for the fan may have worn out. If you have access to a rotation tach (not a timing tach) you can check if your clutch is still in good shape. With your engine at around 4,200 RPMs, your fan should be spinning around 1,400 RPMs. Or, bring up your car to temp and see if it spins “real” freely then spend a few bucks and get a new one or go electric. Also if it has any oil leaking around the clutch for the fan it is probably crap.
In an emergency you can turn your heater on high to cool down the engine a little. It makes it nasty in the car, but it will save your engine.
In an emergency you can turn your heater on high to cool down the engine a little. It makes it nasty in the car, but it will save your engine.
02-07-2006, 11:43 PM
#9
Senior Member
Join Date: May 2005
Location: Choctaw, OK
Posts: 178
It will cool down some if I take it easy, but will not go back to "normal" while I am driving. With the A/C on, 95-100 degree day, driving normal will push the gauge past 3/4 in about ten miles and I usually will not push it past that. I'm not sure if it will continue to overheat if I keep driving,
On the clutch fan front... you should hear your fan 'come on' when your engine heats up. It'll make a whooshing sound like it does a few seconds after you start the engine. Mine started freewheeling a few years ago on a hot august night while I was idling in a Taco Mayo drive-thru about a week after I installed a good engine. Luckily it didn't toast the dowel pins o-rings or the coolant seals. I replaced the clutch fan with an electric fan a few days later.
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