Overheating
Instructor
Joined: Jan 2009
Posts: 129
Likes: 1
From: Tucson AZ
Hook a laptop up to the PCM? Raises several questions.
1. Since I just got the car I do not know where the PCM is located. I can look around or check FSM or you can tell me?
Under the hood, nearest to the windshield, driver's side (1994).
2. The PCM has a serial port? Too old for a USB? or,....
Under the dash, driver's side.
3. Do I need to buy a special cable to go from my computer and PCM?
Yes
4. Do I need special software?....or go into DOS mode and see what happens?
Yes, there are several but I don't know which one works well.
Almost sounds like an OBD scanner tool function?
Any info on this would be appreciated.....or link to a thread....I will do an advanced search in the mean time.
1. Since I just got the car I do not know where the PCM is located. I can look around or check FSM or you can tell me?
Under the hood, nearest to the windshield, driver's side (1994).
2. The PCM has a serial port? Too old for a USB? or,....
Under the dash, driver's side.
3. Do I need to buy a special cable to go from my computer and PCM?
Yes
4. Do I need special software?....or go into DOS mode and see what happens?
Yes, there are several but I don't know which one works well.
Almost sounds like an OBD scanner tool function?
Any info on this would be appreciated.....or link to a thread....I will do an advanced search in the mean time.
Racer
Joined: Oct 2008
Posts: 299
Likes: 1
From: Ottawa Ontario
Ok there's a whole section of this forum dedicated to this stuff.
http://forums.corvetteforum.com/c4-scan-and-tune-82/
Here's what I use as far as Tunercat is concerned and is free for 30 days or 69.00 to purchase:
http://tunercat.com/software/tuner/tnr_setup.zip
You will also need the Y body bin file from them which you need to purchase. For 94 and 95 Corvettes it's $EE.
Lastly You need a cable to connect from a laptop or computer to the car under the driver's side dash. I bought a USB one and it works great from several laptops I've used. It's called an ALDL cable.
I hope this helps.
http://forums.corvetteforum.com/c4-scan-and-tune-82/
Here's what I use as far as Tunercat is concerned and is free for 30 days or 69.00 to purchase:
http://tunercat.com/software/tuner/tnr_setup.zip
You will also need the Y body bin file from them which you need to purchase. For 94 and 95 Corvettes it's $EE.
Lastly You need a cable to connect from a laptop or computer to the car under the driver's side dash. I bought a USB one and it works great from several laptops I've used. It's called an ALDL cable.
I hope this helps.
Instructor
Joined: Jan 2009
Posts: 129
Likes: 1
From: Tucson AZ
You can get the cable here.
http://www.aldlcable.com/sc/details.asp?item=aldlobd2u
The tunercat site is confusing. I can't tell what I would need to get.
I tried several different software packages and could not get any of them to work but maybe something was wrong with the PC I was using.
I was looking at a TechScan 7000 but do not know if it will program the PCM. I emailed them to see if one could do that. Plus it will work on my other ODBII vehicles. Here is its link. You can get it cheaper on Amazon.
http://www.autoxray.com/product_detail.php?pid=136
http://www.aldlcable.com/sc/details.asp?item=aldlobd2u
The tunercat site is confusing. I can't tell what I would need to get.
I tried several different software packages and could not get any of them to work but maybe something was wrong with the PC I was using.
I was looking at a TechScan 7000 but do not know if it will program the PCM. I emailed them to see if one could do that. Plus it will work on my other ODBII vehicles. Here is its link. You can get it cheaper on Amazon.
http://www.autoxray.com/product_detail.php?pid=136
Drifting
Joined: Sep 2003
Posts: 1,363
Likes: 7
From: 1994 LT1 Coupe 6-speed with FX3 & 2000 LS1 Vert 6-Speed with F45 Hunterdon County, NJ
K.C.E.,
Before reprogramming things, suggest considering you actually might have a slight problem with your coolant system.
The digital dash coolant temperature is derived from the Electronic Coolant Temperature (ECT) sensor mounted in the water pump.
By contrast, the analog gauge coolant temperature is derived from an old style coolant sensor mounted in the rear passenger side block/head of the engine.
If the coolant is moving through the engine properly (and assuming sensors and gauges are operating correctly), then both temperature gauges should be about the same (i.e. our 94 are = +/- 5 degrees F).
However, if something is preventing the cooler water introduced into the water pump via the thermostat (remember the LT1 engine has a reverse coolant flow) from properly mixing with the hot coolant in the engine, or preventing the cooled-down coolant from being directed into the heads/block, then it can cause the rear of the engine to be much hotter than the front, which IS NOT GOOD.
This can be caused by:
1. wrong/bad/old/failing thermostat. Although it doesn't sound like your thermostat is wrong based on temps (LT1 thermostats are quite different than most), it could be an aftermarket brand which doesn't open as much or as quickly -- or just old/tired -- or it could have a mechanical problem -- where the lower plate is slipping off the main plunger, causing a reduction in the openning size, and thereby an increased coolant temps (this happened to our 94, and when replaced, dropped the temps 15-20 degrees F).
2. Old/wrong anti-freeze -- our 94 takes the old style green anti-freeze (getting difficult to find e.g. Texaco brand available at FX/Driver) -- anti-freeze older than 2 years may have trouble preventing spot-boiling within the engine, causing air-pockets which can restrict coolant movement, until higher RPM's start to move it around.
3. bad/failing flow-restrictor -- mounted in the 'inlet' heater hose to the heater core is a spring-operated plastic flow-restrictor -- designed to limit flow pressure to the heater-core at higher rpm's, but allowing full flow at lower rpms -- if the spring is 'tired' or the moving restrictor inside is stuck, it could allow it to 'restrict' flow when it should not, reducing the heater core's assistance in keeping the engine cool.
4. vapor pipes partially clogged -- the LT1 engine has two 'vapor' pipes mounted on the back-side of the heads, which route water and vapor to the black pressure tank where it is 'scavenged' into the air-bubble which is maintained in the pressure tank to allow/maintain pressure in the coolant system. Test for flow by removing the radiator cap, pinching the small hose from the passenger top side of radiator, and looking for water squirting into the pressure tank via the small hose (may need to remove some coolant from the tank to verify/see this).
5. 'junk' in the engine block/heads coolant passageways -- a good flushing should fix this -- manual says to remove 'knock' sensors to properly drain block -- alternative is multiple drain/refill with distilled water/run cycles with shop-vac in blower mode on black pressure tank to help push out 'junk' through the radiator drain (passenger side of radiator).
6. corrosion on coolant sensors plugs -- since the gauges 'read' the resistance of the sensors, sometimes just removing and reinstalling with a squirt of WD-40 or electrical contact cleaner, could cause the gauges to read different temperatures.
Before reprogramming things, suggest considering you actually might have a slight problem with your coolant system.
The digital dash coolant temperature is derived from the Electronic Coolant Temperature (ECT) sensor mounted in the water pump.
By contrast, the analog gauge coolant temperature is derived from an old style coolant sensor mounted in the rear passenger side block/head of the engine.
If the coolant is moving through the engine properly (and assuming sensors and gauges are operating correctly), then both temperature gauges should be about the same (i.e. our 94 are = +/- 5 degrees F).
However, if something is preventing the cooler water introduced into the water pump via the thermostat (remember the LT1 engine has a reverse coolant flow) from properly mixing with the hot coolant in the engine, or preventing the cooled-down coolant from being directed into the heads/block, then it can cause the rear of the engine to be much hotter than the front, which IS NOT GOOD.
This can be caused by:
1. wrong/bad/old/failing thermostat. Although it doesn't sound like your thermostat is wrong based on temps (LT1 thermostats are quite different than most), it could be an aftermarket brand which doesn't open as much or as quickly -- or just old/tired -- or it could have a mechanical problem -- where the lower plate is slipping off the main plunger, causing a reduction in the openning size, and thereby an increased coolant temps (this happened to our 94, and when replaced, dropped the temps 15-20 degrees F).
2. Old/wrong anti-freeze -- our 94 takes the old style green anti-freeze (getting difficult to find e.g. Texaco brand available at FX/Driver) -- anti-freeze older than 2 years may have trouble preventing spot-boiling within the engine, causing air-pockets which can restrict coolant movement, until higher RPM's start to move it around.
3. bad/failing flow-restrictor -- mounted in the 'inlet' heater hose to the heater core is a spring-operated plastic flow-restrictor -- designed to limit flow pressure to the heater-core at higher rpm's, but allowing full flow at lower rpms -- if the spring is 'tired' or the moving restrictor inside is stuck, it could allow it to 'restrict' flow when it should not, reducing the heater core's assistance in keeping the engine cool.
4. vapor pipes partially clogged -- the LT1 engine has two 'vapor' pipes mounted on the back-side of the heads, which route water and vapor to the black pressure tank where it is 'scavenged' into the air-bubble which is maintained in the pressure tank to allow/maintain pressure in the coolant system. Test for flow by removing the radiator cap, pinching the small hose from the passenger top side of radiator, and looking for water squirting into the pressure tank via the small hose (may need to remove some coolant from the tank to verify/see this).
5. 'junk' in the engine block/heads coolant passageways -- a good flushing should fix this -- manual says to remove 'knock' sensors to properly drain block -- alternative is multiple drain/refill with distilled water/run cycles with shop-vac in blower mode on black pressure tank to help push out 'junk' through the radiator drain (passenger side of radiator).
6. corrosion on coolant sensors plugs -- since the gauges 'read' the resistance of the sensors, sometimes just removing and reinstalling with a squirt of WD-40 or electrical contact cleaner, could cause the gauges to read different temperatures.
Thread Starter
Racer
Joined: Oct 2008
Posts: 250
Likes: 5
From: Winchester VA
K.C.E.,
Before reprogramming things, suggest considering you actually might have a slight problem with your coolant system.
The digital dash coolant temperature is derived from the Electronic Coolant Temperature (ECT) sensor mounted in the water pump.
By contrast, the analog gauge coolant temperature is derived from an old style coolant sensor mounted in the rear passenger side block/head of the engine.
If the coolant is moving through the engine properly (and assuming sensors and gauges are operating correctly), then both temperature gauges should be about the same (i.e. our 94 are = +/- 5 degrees F).
However, if something is preventing the cooler water introduced into the water pump via the thermostat (remember the LT1 engine has a reverse coolant flow) from properly mixing with the hot coolant in the engine, or preventing the cooled-down coolant from being directed into the heads/block, then it can cause the rear of the engine to be much hotter than the front, which IS NOT GOOD.
This can be caused by:
1. wrong/bad/old/failing thermostat. Although it doesn't sound like your thermostat is wrong based on temps (LT1 thermostats are quite different than most), it could be an aftermarket brand which doesn't open as much or as quickly -- or just old/tired -- or it could have a mechanical problem -- where the lower plate is slipping off the main plunger, causing a reduction in the openning size, and thereby an increased coolant temps (this happened to our 94, and when replaced, dropped the temps 15-20 degrees F).
2. Old/wrong anti-freeze -- our 94 takes the old style green anti-freeze (getting difficult to find e.g. Texaco brand available at FX/Driver) -- anti-freeze older than 2 years may have trouble preventing spot-boiling within the engine, causing air-pockets which can restrict coolant movement, until higher RPM's start to move it around.
3. bad/failing flow-restrictor -- mounted in the 'inlet' heater hose to the heater core is a spring-operated plastic flow-restrictor -- designed to limit flow pressure to the heater-core at higher rpm's, but allowing full flow at lower rpms -- if the spring is 'tired' or the moving restrictor inside is stuck, it could allow it to 'restrict' flow when it should not, reducing the heater core's assistance in keeping the engine cool.
4. vapor pipes partially clogged -- the LT1 engine has two 'vapor' pipes mounted on the back-side of the heads, which route water and vapor to the black pressure tank where it is 'scavenged' into the air-bubble which is maintained in the pressure tank to allow/maintain pressure in the coolant system. Test for flow by removing the radiator cap, pinching the small hose from the passenger top side of radiator, and looking for water squirting into the pressure tank via the small hose (may need to remove some coolant from the tank to verify/see this).
5. 'junk' in the engine block/heads coolant passageways -- a good flushing should fix this -- manual says to remove 'knock' sensors to properly drain block -- alternative is multiple drain/refill with distilled water/run cycles with shop-vac in blower mode on black pressure tank to help push out 'junk' through the radiator drain (passenger side of radiator).
6. corrosion on coolant sensors plugs -- since the gauges 'read' the resistance of the sensors, sometimes just removing and reinstalling with a squirt of WD-40 or electrical contact cleaner, could cause the gauges to read different temperatures.
Before reprogramming things, suggest considering you actually might have a slight problem with your coolant system.
The digital dash coolant temperature is derived from the Electronic Coolant Temperature (ECT) sensor mounted in the water pump.
By contrast, the analog gauge coolant temperature is derived from an old style coolant sensor mounted in the rear passenger side block/head of the engine.
If the coolant is moving through the engine properly (and assuming sensors and gauges are operating correctly), then both temperature gauges should be about the same (i.e. our 94 are = +/- 5 degrees F).
However, if something is preventing the cooler water introduced into the water pump via the thermostat (remember the LT1 engine has a reverse coolant flow) from properly mixing with the hot coolant in the engine, or preventing the cooled-down coolant from being directed into the heads/block, then it can cause the rear of the engine to be much hotter than the front, which IS NOT GOOD.
This can be caused by:
1. wrong/bad/old/failing thermostat. Although it doesn't sound like your thermostat is wrong based on temps (LT1 thermostats are quite different than most), it could be an aftermarket brand which doesn't open as much or as quickly -- or just old/tired -- or it could have a mechanical problem -- where the lower plate is slipping off the main plunger, causing a reduction in the openning size, and thereby an increased coolant temps (this happened to our 94, and when replaced, dropped the temps 15-20 degrees F).
2. Old/wrong anti-freeze -- our 94 takes the old style green anti-freeze (getting difficult to find e.g. Texaco brand available at FX/Driver) -- anti-freeze older than 2 years may have trouble preventing spot-boiling within the engine, causing air-pockets which can restrict coolant movement, until higher RPM's start to move it around.
3. bad/failing flow-restrictor -- mounted in the 'inlet' heater hose to the heater core is a spring-operated plastic flow-restrictor -- designed to limit flow pressure to the heater-core at higher rpm's, but allowing full flow at lower rpms -- if the spring is 'tired' or the moving restrictor inside is stuck, it could allow it to 'restrict' flow when it should not, reducing the heater core's assistance in keeping the engine cool.
4. vapor pipes partially clogged -- the LT1 engine has two 'vapor' pipes mounted on the back-side of the heads, which route water and vapor to the black pressure tank where it is 'scavenged' into the air-bubble which is maintained in the pressure tank to allow/maintain pressure in the coolant system. Test for flow by removing the radiator cap, pinching the small hose from the passenger top side of radiator, and looking for water squirting into the pressure tank via the small hose (may need to remove some coolant from the tank to verify/see this).
5. 'junk' in the engine block/heads coolant passageways -- a good flushing should fix this -- manual says to remove 'knock' sensors to properly drain block -- alternative is multiple drain/refill with distilled water/run cycles with shop-vac in blower mode on black pressure tank to help push out 'junk' through the radiator drain (passenger side of radiator).
6. corrosion on coolant sensors plugs -- since the gauges 'read' the resistance of the sensors, sometimes just removing and reinstalling with a squirt of WD-40 or electrical contact cleaner, could cause the gauges to read different temperatures.
Thanks for explaining the location of the 2 sensors and their difference. You provided a lot of good information. I have been so busy at work/home I have not had time to read the FSM or even pop the hood. I have not driven the car to work since the experience and did not want to until I am confident this issue is resolved. I will drive it locally and keep an eye on it. My drive to work has a lot of country roads and sometimes no way of pulling off the road.
I am not considering the idea reprogramming anything until I am convinced everything is running as designed....but I am very intrigued with the idea.....
It still bothers me how quickly the needle dropped when I hit the aftermarket "on/off" switches on my center console that turned the fans on. I just can not believe the temperature of the water could ever drop that quickly. The analog went from almost maximum down to match the digital. Again, I am going to drive it locally and play with the fan switch more to see what is going on.....one data point does not provide good statistics!
I am still weighing out the issues trying to decide my next step. We do have some good Corvette shops in the area and I am tempted to just drop it off and tell them to flush it, change the hoses and thermostat, and check out everything and take the financial hit......or I might take a few days off from work and jump into it and do all of it (as well as work on house,yard, the 4runner which has a water leak between the back of the engine and the firewall, etc.) .....still thinking it through.
I will probably at minimum check the electrical connections on both gages and then spray with electrical cleaner and then WD40.
kce
Thread Starter
Racer
Joined: Oct 2008
Posts: 250
Likes: 5
From: Winchester VA
Hook a laptop up to the PCM? Raises several questions.
1. Since I just got the car I do not know where the PCM is located. I can look around or check FSM or you can tell me?
Under the hood, nearest to the windshield, driver's side (1994).
2. The PCM has a serial port? Too old for a USB? or,....
Under the dash, driver's side.
3. Do I need to buy a special cable to go from my computer and PCM?
Yes
4. Do I need special software?....or go into DOS mode and see what happens?
Yes, there are several but I don't know which one works well.
Almost sounds like an OBD scanner tool function?
Any info on this would be appreciated.....or link to a thread....I will do an advanced search in the mean time.
1. Since I just got the car I do not know where the PCM is located. I can look around or check FSM or you can tell me?
Under the hood, nearest to the windshield, driver's side (1994).
2. The PCM has a serial port? Too old for a USB? or,....
Under the dash, driver's side.
3. Do I need to buy a special cable to go from my computer and PCM?
Yes
4. Do I need special software?....or go into DOS mode and see what happens?
Yes, there are several but I don't know which one works well.
Almost sounds like an OBD scanner tool function?
Any info on this would be appreciated.....or link to a thread....I will do an advanced search in the mean time.
Instructor
Joined: Jan 2009
Posts: 129
Likes: 1
From: Tucson AZ
Well, those are exactly the things I want to do. Anybody in Tucson have one of these so I can see it in action?
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