origionally posted by Shawndude:
SONIC TECH NOTE SERIES:
Preventative Maintenance Tech Notes 1987 to 1992 Supra MA-70 & 71 Series Non Turbo & Turbo v4.0
Information provided is given free of charge in good faith without prejudice
Table of Contents
Section 1 7M-GE & GTE Engines
1.0 Idling problems
1.1 Head gaskets
1.2 Valve Adjustment & Misc
1.3 Cooling System
1.4 Intercooler System {Turbo Only}
1.5 ODD codes {knock Sensor Code}
1.6 Oil pressure / 7M engines
1.7 7M Cylinder Head Work and machining
Section 2 Drive Train
2.0 Transmission
2.1 Drive Shafts
2.2 Differential Carriers
2.3 Front & Rear Wheel Bearings
Section 3 Suspension
3.0 Front Lower A Arms
Section 4 Brakes
4.0 Brake service
_____________________________
Section 1 ~7M-GE & GTE Engines 1.0: Idling problems
On a warm day, when restarting the engine, as when leaving a gas station or coffee shop after a short visit, the 7M-GE and 7M-GTE engines may exhibit weak idling, hard starting and putting around at 500 rpm for a short period. If this happens only very occasionally it is perfectly normal and is caused by a condition called HEAT SOAK, which happens, after shutting off the engine. After shutdown the water pump and fan are no longer cooling the engine so the heat from inside the engine comes out into to engine bay cooking everything in its way, EFI sensors say "Wako sure is hot in here," gasoline in the fuel rail on the intake manifold is boiled {not to mention a host of other thermodynamic conditions that occur after shutdown}. All Engineering levels are taxed.
To combat this inherit EFI {Electronic Fuel Injection} problem a number factory installed electronic and mechanical engine control systems are used, but under certain conditions they fail to correct the problem completely. For the most part EFI is a wonderful system allowing great fuel economy and silky smooth drive ability so a small bug like HEAT SOAK is still a more livable end than going back to carbs. If this rough idling symptom is happening more often than seems normal there may be a problem with one or more of the following: Cold start injector time switch, Bad Fuel, Throttle position sensor, Plugged or restricted fuel filter or gas cap, Idle speed solenoid air valve (ISC Valve), Fuel pressure, 2 speed fuel pump system, Head Gasket, Air intake leaks, Engine mechanical, Fuel pressure up VSV {vacuum switching valve}.
Other points to remember about the idle speed control valve (ISC valve) are: After shutting of the engine you should here a faint clicking sound for a short time after the engine is killed, this is normal operation.
Unplug the wire at the ISC valve after the valve makes its normal clicking noise after engine is shut off, will cause the engine to run in high idle when the engine is restarted. This is a good sign that the ISC valve is working correctly.
When E1 & T1 in the check connector (Diag Block) are shorted, this will cause the valve to go to a standard closed position. This is the first step in setting the curb idle and ignition timing.
Failure of the ISC valve is not a common problem, what should be checked is the seat section of the valve that sits in the intake manifold. When the ISC valve is removed, this seat will remain in the hole in the intake manifold. This seat valve will get sticky and not work smoothly due to excess carbon and deposits in the intake manifold.
The Bardal Super Tune kit comes with a can of gunk for the fuel tank and a can of gunk to be slowly sucked into the intake manifold while the engine is running at high idle. This gunk stuff works great. Also included in the Bardal super tune kit is a can of gunk that is sprayed into the intake plumbing, and throttle body. Spray this gunk into the airline going into the idle speed control valve. Presto changeo the valve will most often work fine again. Wins also makes a good fuel injection cleaning kit that works wonders as well. The Wynns kit does not have the can of gunk spray, but it does a great job on the injectors and intake manifold.
When the VSV for fuel pressure up is working correctly it allows the fuel pressure regulator to receive atmospheric air pressure to its vacuum port when the engine is hot. To test this VSV you can unplug the vacuum line from the fuel pressure regulator and start the car to see if the vehicle starts normally. If it does the fuel pressure up VSV is the problem.
1.1: Head gaskets
I have worked with a few unfortunate club members who have experienced grief with their 7M-GE and 7M-GTE engines due to cylinder heads that had lost their head bolt tension becoming so loose they actually allow the head gasket to oscillate inside the engine block between the cylinder head and block deck surface, thus damaging the cylinder head and the block deck surfaces. Damage resulting in Toyota replacing some entire engine blocks and heads on warranty. This is a very sad thing because the 7M-GE and 7M-GTE engines are designed from the factory to be bulletproof but this problem has tarnished the long-standing reputation for Supra reliability. This tech note series will teach you how to make your Supra with the 7M-GE or GTE engine as bulletproof as Toyota intended it to be.
There are several ways to detect whether your engines head gasket is ok. The best method is to have a service shop, or a friend who owns a block test kit tests your system for a compression leak to your cooling system. If unavailable this test kit can be purchased from a Snap On dealer or contact the manufacturer for dealer in your area. This is a test unit and test fluid that changes color with the presence of exhaust gas in the engine coolant, the kit cost about 50 dollars Canadian to purchase and is good for many tests. Another test that should be completed is a coolant system pressure test, test your system for leaks with five to ten PSI pressure. If your engine passes these tests continue reading to find out what has to be done to keep it that way.
If your system is leaking it is too late for a simple head re-torque. Usually the factory OEM installed gasket looks like mush when the engine is disassembled after a failure. Some of the Head bolts are loose when the engine comes apart. Coolant passages and sealing rings are distorted and compressed out of shape. The exhaust side of this engine runs very hot due to the exhaust manifold and catalytic converter design that locates the catalytic converter right beside the engine block. The manifold and catalytic converter add a tremendous amount of heat to this side of the engine block.
It is always better to know that your gasket is starting to leak than to wait until the engine burns up enough coolant to cause it to overheat. In all cases when the gasket is changed before the engine overheats and starts consuming large amounts of coolant the repair is simple and straightforward.
After the head gasket has failed, a combustion leak that goes undetected leads to immediate destroying of the inhibitors in the coolant, and will set up an acid condition in the cooling system. The acidic coolant will then conduct electricity, and a galvanizing reaction will begin among the various kinds of metals in the cooling system. This will eat away at the radiator and other parts of the system from the inside out. When the coolant enters the cylinders the result is a poorly running engine, cutting engine life with each revolution as the coolant breaks down the engine's lubricants. Combustion leaks in the compression ring area also force coolant away during acceleration causing excessive heat. When acceleration stops, the diverted coolant rushes back to the area, resulting in rapid temperature changes. This is bad enough, but the compression leak also causes the engine to blow the coolant out of the radiator and cylinder head into the overflow reservoir bottle, depleting the coolant, causing the engine to badly overheat. This heat further aggravates the already devastating conditions in the engine by causing the metal alloy in the cylinder head to expand, stretching the head bolts and further compressing the bad head gasket.
After the engine cools down the head bolt tension due to the heat expansion is relieved, leaving what is left of the original head bolt tension from the torque up at the factory. Due to the mashed head gasket, internal surface damage, and warped cylinder head, the factory bolt elongation is all but used up.
Recently I purchased a pair of new head bolts from my local Toyota dealership. One bolt from the 1995 Supra 2JZ-GTE engines, as well as a new bolt from the 7M-GTE. I then contracted a local certified engineering metallurgical company to perform tensile strength tests on the head bolts to compare yield strengths and torque values.
I have lab data reports based on the ASTM A370 tensile test, giving tensile strength, yield strength, ultimate load, yield load, as well as deformation data and maximum tightening torque values for the head bolts from the 2JZ GTE and 7M-GTE engines. Some results of the test are given below.
7M head bolt is: 12mm-1.25mm thread pitch {Property Class 10.9 grade 8} yield strength=147,353 PSI... tensile strength=160,550 PSI... ultimate load=70,198 N... % elongation=17... % reduction of area=66 2J head bolt is: 11mm-1.25mm thread pitch {Property Class 10.9 grade 8} yield strength=148,948 PSI... tensile strength=162,581 PSI... ultimate load=68,997 N... % elongation=19... % reduction of area=66
The metals used in the head bolts of the 7M & 2JZ engines are identical in metallurgy +/- manufacturing S.P.C. This is a good material; it stretches smoothly in the plastic region of the curve before it snaps.
By calculating the unit strain for each of the different areas of bolts based on the average yield strength, the following total elongation numbers were calculated. The 7M bolt has a total elongation of .0134" {.3399mm}, and the 2JZ bolt has a total elongation of .01093" {.2775mm}.
By comparing the elongation differences of the bolts, related to the corresponding different thickness of the aluminum in the engines cylinder heads, and allowing for the total length of the bolt shank plus 50% of the length of the threads, the only apparent difference is that the 2JZ bolt has 36 percent more thread than the 7M bolt does. The 7M & 2JZ bolts appear to be designed with the same steel to aluminum expansion stretch theory. I believe the bolt designs are different only because of the different ratio of the bolts metal area versus the thickness of the aluminum cylinder heads the bolt is designed to hold down. The torquing procedure for the two head bolts is also different, as is the head gasket
Toyota service manuals say that the 7M engines head bolt torque specification is 52 to 58 ft. lbs. According to my findings the 52 to 58 ft. lbs. specification for the 7M might be too low a torque value to keep the bolt in acceptable tension, not to mention the normal compression of the head gasket after time. As mentioned earlier many 7M engines that experience head gasket failures have many head bolts that can be removed from the engines failed cylinders by hand, or are very loose when removed.
My calculations show that the 7M head bolts when torqued to the factory specifications of 52 to 58 ft. lbs. is in very low tension related to the bolts actual yield curve. Calculations based on my test data show torque values for the 7M head bolt could be as high as 68 ft. lbs. to 72 ft. lbs. without putting the bolt into the plastic region. On a cold engine this extra torque would allow more tension on the head bolts after the head gasket compresses to normal operating thickness.
Many Supra owners that can afford it are upgrading their 7M engine to the expensive HKS stopper type metal head gasket for the 7M engine. This gasket comes in a number of different thick nesses. My Company stocks the HKS gaskets and I ship them all over the world. The HKS gasket will hold well to over 20 PSI of boost over 400 hp as sea level with upgraded fuel and turbochargers. The factory head bolt torque may be satisfactory with a metal head gasket since metal head gaskets do not deform as much as the soft OEM gasket used in the 7M. I would still recommend torquing the bolts to 72-ft. lbs. When upgrading to Metal head gaskets much must be considered with regard to machine work and the finish of the engine block deck and cylinder head gasket surface. See the following link for full details on doing correct machine work to your engine;
http://www.supras.com/~riemer/HKS/hksgaskets.html
I have many club members running well over 20 lbs boost at sea level with no head or engine failures using the metal head gasket. This problem is not exclusive to the Toyota Supra! Many other automotive manufactures have this problem with their engines: Ford, GM, Chrysler & Mitsubishi to mention a few. Good head gasket condition is a fact of life with any high output engine. GM is currently working with new head surfacing techniques that will hopefully solve their problems with the QUAD 4 and others.
The solution to diverting this problem has turned out to be a simple lesson from the old book of Forgotten Fundamentals 101, chapter one "MAKE SURE THE DARN THING IS ON TIGHT". The only problem with this statement is that for some of the 7M's it is too late the gasket may already be bad. The head bolts needed to be re-torqued after the first 20,000.00 km's or tomorrow if yours has never been done, you may be able to save yourself a future head gasket repair job. I recommend a higher torque value than the factory, 70 foot/pounds versus 58 foot/pounds. Re-torquing the head is not a hard thing to do if you have mechanical background skills and the correct tools including the SST {Specialty Service Tool} for the head bolts. If you are uneasy about doing it I will recommend you to a club member or service shop in your area.
SONIC TECH NOTE SERIES:
Preventative Maintenance Tech Notes 1987 to 1992 Supra MA-70 & 71 Series Non Turbo & Turbo v4.0
Information provided is given free of charge in good faith without prejudice
Table of Contents
Section 1 7M-GE & GTE Engines
1.0 Idling problems
1.1 Head gaskets
1.2 Valve Adjustment & Misc
1.3 Cooling System
1.4 Intercooler System {Turbo Only}
1.5 ODD codes {knock Sensor Code}
1.6 Oil pressure / 7M engines
1.7 7M Cylinder Head Work and machining
Section 2 Drive Train
2.0 Transmission
2.1 Drive Shafts
2.2 Differential Carriers
2.3 Front & Rear Wheel Bearings
Section 3 Suspension
3.0 Front Lower A Arms
Section 4 Brakes
4.0 Brake service
_____________________________
Section 1 ~7M-GE & GTE Engines 1.0: Idling problems
On a warm day, when restarting the engine, as when leaving a gas station or coffee shop after a short visit, the 7M-GE and 7M-GTE engines may exhibit weak idling, hard starting and putting around at 500 rpm for a short period. If this happens only very occasionally it is perfectly normal and is caused by a condition called HEAT SOAK, which happens, after shutting off the engine. After shutdown the water pump and fan are no longer cooling the engine so the heat from inside the engine comes out into to engine bay cooking everything in its way, EFI sensors say "Wako sure is hot in here," gasoline in the fuel rail on the intake manifold is boiled {not to mention a host of other thermodynamic conditions that occur after shutdown}. All Engineering levels are taxed.
To combat this inherit EFI {Electronic Fuel Injection} problem a number factory installed electronic and mechanical engine control systems are used, but under certain conditions they fail to correct the problem completely. For the most part EFI is a wonderful system allowing great fuel economy and silky smooth drive ability so a small bug like HEAT SOAK is still a more livable end than going back to carbs. If this rough idling symptom is happening more often than seems normal there may be a problem with one or more of the following: Cold start injector time switch, Bad Fuel, Throttle position sensor, Plugged or restricted fuel filter or gas cap, Idle speed solenoid air valve (ISC Valve), Fuel pressure, 2 speed fuel pump system, Head Gasket, Air intake leaks, Engine mechanical, Fuel pressure up VSV {vacuum switching valve}.
Other points to remember about the idle speed control valve (ISC valve) are: After shutting of the engine you should here a faint clicking sound for a short time after the engine is killed, this is normal operation.
Unplug the wire at the ISC valve after the valve makes its normal clicking noise after engine is shut off, will cause the engine to run in high idle when the engine is restarted. This is a good sign that the ISC valve is working correctly.
When E1 & T1 in the check connector (Diag Block) are shorted, this will cause the valve to go to a standard closed position. This is the first step in setting the curb idle and ignition timing.
Failure of the ISC valve is not a common problem, what should be checked is the seat section of the valve that sits in the intake manifold. When the ISC valve is removed, this seat will remain in the hole in the intake manifold. This seat valve will get sticky and not work smoothly due to excess carbon and deposits in the intake manifold.
The Bardal Super Tune kit comes with a can of gunk for the fuel tank and a can of gunk to be slowly sucked into the intake manifold while the engine is running at high idle. This gunk stuff works great. Also included in the Bardal super tune kit is a can of gunk that is sprayed into the intake plumbing, and throttle body. Spray this gunk into the airline going into the idle speed control valve. Presto changeo the valve will most often work fine again. Wins also makes a good fuel injection cleaning kit that works wonders as well. The Wynns kit does not have the can of gunk spray, but it does a great job on the injectors and intake manifold.
When the VSV for fuel pressure up is working correctly it allows the fuel pressure regulator to receive atmospheric air pressure to its vacuum port when the engine is hot. To test this VSV you can unplug the vacuum line from the fuel pressure regulator and start the car to see if the vehicle starts normally. If it does the fuel pressure up VSV is the problem.
1.1: Head gaskets
I have worked with a few unfortunate club members who have experienced grief with their 7M-GE and 7M-GTE engines due to cylinder heads that had lost their head bolt tension becoming so loose they actually allow the head gasket to oscillate inside the engine block between the cylinder head and block deck surface, thus damaging the cylinder head and the block deck surfaces. Damage resulting in Toyota replacing some entire engine blocks and heads on warranty. This is a very sad thing because the 7M-GE and 7M-GTE engines are designed from the factory to be bulletproof but this problem has tarnished the long-standing reputation for Supra reliability. This tech note series will teach you how to make your Supra with the 7M-GE or GTE engine as bulletproof as Toyota intended it to be.
There are several ways to detect whether your engines head gasket is ok. The best method is to have a service shop, or a friend who owns a block test kit tests your system for a compression leak to your cooling system. If unavailable this test kit can be purchased from a Snap On dealer or contact the manufacturer for dealer in your area. This is a test unit and test fluid that changes color with the presence of exhaust gas in the engine coolant, the kit cost about 50 dollars Canadian to purchase and is good for many tests. Another test that should be completed is a coolant system pressure test, test your system for leaks with five to ten PSI pressure. If your engine passes these tests continue reading to find out what has to be done to keep it that way.
If your system is leaking it is too late for a simple head re-torque. Usually the factory OEM installed gasket looks like mush when the engine is disassembled after a failure. Some of the Head bolts are loose when the engine comes apart. Coolant passages and sealing rings are distorted and compressed out of shape. The exhaust side of this engine runs very hot due to the exhaust manifold and catalytic converter design that locates the catalytic converter right beside the engine block. The manifold and catalytic converter add a tremendous amount of heat to this side of the engine block.
It is always better to know that your gasket is starting to leak than to wait until the engine burns up enough coolant to cause it to overheat. In all cases when the gasket is changed before the engine overheats and starts consuming large amounts of coolant the repair is simple and straightforward.
After the head gasket has failed, a combustion leak that goes undetected leads to immediate destroying of the inhibitors in the coolant, and will set up an acid condition in the cooling system. The acidic coolant will then conduct electricity, and a galvanizing reaction will begin among the various kinds of metals in the cooling system. This will eat away at the radiator and other parts of the system from the inside out. When the coolant enters the cylinders the result is a poorly running engine, cutting engine life with each revolution as the coolant breaks down the engine's lubricants. Combustion leaks in the compression ring area also force coolant away during acceleration causing excessive heat. When acceleration stops, the diverted coolant rushes back to the area, resulting in rapid temperature changes. This is bad enough, but the compression leak also causes the engine to blow the coolant out of the radiator and cylinder head into the overflow reservoir bottle, depleting the coolant, causing the engine to badly overheat. This heat further aggravates the already devastating conditions in the engine by causing the metal alloy in the cylinder head to expand, stretching the head bolts and further compressing the bad head gasket.
After the engine cools down the head bolt tension due to the heat expansion is relieved, leaving what is left of the original head bolt tension from the torque up at the factory. Due to the mashed head gasket, internal surface damage, and warped cylinder head, the factory bolt elongation is all but used up.
Recently I purchased a pair of new head bolts from my local Toyota dealership. One bolt from the 1995 Supra 2JZ-GTE engines, as well as a new bolt from the 7M-GTE. I then contracted a local certified engineering metallurgical company to perform tensile strength tests on the head bolts to compare yield strengths and torque values.
I have lab data reports based on the ASTM A370 tensile test, giving tensile strength, yield strength, ultimate load, yield load, as well as deformation data and maximum tightening torque values for the head bolts from the 2JZ GTE and 7M-GTE engines. Some results of the test are given below.
7M head bolt is: 12mm-1.25mm thread pitch {Property Class 10.9 grade 8} yield strength=147,353 PSI... tensile strength=160,550 PSI... ultimate load=70,198 N... % elongation=17... % reduction of area=66 2J head bolt is: 11mm-1.25mm thread pitch {Property Class 10.9 grade 8} yield strength=148,948 PSI... tensile strength=162,581 PSI... ultimate load=68,997 N... % elongation=19... % reduction of area=66
The metals used in the head bolts of the 7M & 2JZ engines are identical in metallurgy +/- manufacturing S.P.C. This is a good material; it stretches smoothly in the plastic region of the curve before it snaps.
By calculating the unit strain for each of the different areas of bolts based on the average yield strength, the following total elongation numbers were calculated. The 7M bolt has a total elongation of .0134" {.3399mm}, and the 2JZ bolt has a total elongation of .01093" {.2775mm}.
By comparing the elongation differences of the bolts, related to the corresponding different thickness of the aluminum in the engines cylinder heads, and allowing for the total length of the bolt shank plus 50% of the length of the threads, the only apparent difference is that the 2JZ bolt has 36 percent more thread than the 7M bolt does. The 7M & 2JZ bolts appear to be designed with the same steel to aluminum expansion stretch theory. I believe the bolt designs are different only because of the different ratio of the bolts metal area versus the thickness of the aluminum cylinder heads the bolt is designed to hold down. The torquing procedure for the two head bolts is also different, as is the head gasket
Toyota service manuals say that the 7M engines head bolt torque specification is 52 to 58 ft. lbs. According to my findings the 52 to 58 ft. lbs. specification for the 7M might be too low a torque value to keep the bolt in acceptable tension, not to mention the normal compression of the head gasket after time. As mentioned earlier many 7M engines that experience head gasket failures have many head bolts that can be removed from the engines failed cylinders by hand, or are very loose when removed.
My calculations show that the 7M head bolts when torqued to the factory specifications of 52 to 58 ft. lbs. is in very low tension related to the bolts actual yield curve. Calculations based on my test data show torque values for the 7M head bolt could be as high as 68 ft. lbs. to 72 ft. lbs. without putting the bolt into the plastic region. On a cold engine this extra torque would allow more tension on the head bolts after the head gasket compresses to normal operating thickness.
Many Supra owners that can afford it are upgrading their 7M engine to the expensive HKS stopper type metal head gasket for the 7M engine. This gasket comes in a number of different thick nesses. My Company stocks the HKS gaskets and I ship them all over the world. The HKS gasket will hold well to over 20 PSI of boost over 400 hp as sea level with upgraded fuel and turbochargers. The factory head bolt torque may be satisfactory with a metal head gasket since metal head gaskets do not deform as much as the soft OEM gasket used in the 7M. I would still recommend torquing the bolts to 72-ft. lbs. When upgrading to Metal head gaskets much must be considered with regard to machine work and the finish of the engine block deck and cylinder head gasket surface. See the following link for full details on doing correct machine work to your engine;
http://www.supras.com/~riemer/HKS/hksgaskets.html
I have many club members running well over 20 lbs boost at sea level with no head or engine failures using the metal head gasket. This problem is not exclusive to the Toyota Supra! Many other automotive manufactures have this problem with their engines: Ford, GM, Chrysler & Mitsubishi to mention a few. Good head gasket condition is a fact of life with any high output engine. GM is currently working with new head surfacing techniques that will hopefully solve their problems with the QUAD 4 and others.
The solution to diverting this problem has turned out to be a simple lesson from the old book of Forgotten Fundamentals 101, chapter one "MAKE SURE THE DARN THING IS ON TIGHT". The only problem with this statement is that for some of the 7M's it is too late the gasket may already be bad. The head bolts needed to be re-torqued after the first 20,000.00 km's or tomorrow if yours has never been done, you may be able to save yourself a future head gasket repair job. I recommend a higher torque value than the factory, 70 foot/pounds versus 58 foot/pounds. Re-torquing the head is not a hard thing to do if you have mechanical background skills and the correct tools including the SST {Specialty Service Tool} for the head bolts. If you are uneasy about doing it I will recommend you to a club member or service shop in your area.