Replace normal engine in 87 supra with turbo 7mgt, complete with harness and computer. the tac did not work, the temp gauge reads hot at all time, key on engine not started it reads hot. changed cluster and tac works but temp is the same way. changed sending unit and no different, reads hot. also turbo boost gauge stays all the way up.need help with this please.

Hi Bill, is the engine actually getting hot enough for the fans to come on? if the engine does have overheating problem (but you say the temp gauge reads normal) then i would check the operation of the engine temp switch, there are two, one for the gauge and one for the fans.

I'll put my bets on a faulty gage...but that's just me.

I think you correct in thinking the sending unit is bad, this is a common problem. if the temp gauge reads hot and the engine is running normal and there is no coolant overflowing onto the ground and the radidator is full then i would have to say that the car is not really overheating but rather the sending unit is bad, i would replace the unit and go from there. these trucks run up to above the three quater mark on the gauge at times before the cooling fans are turned on by the computer. hope this is helpful.

The boost gauge is fed by the Turbo. It tells you how much extra air the turbo is putting into your engine. This is turbo ONLY. Usually a little plastic line from the turbo to the gauge.

The gauge is working fine, the turbo will not kick in untill the engine is spinning fast enough, as the turbo is propelled by exaughst from the engine. So, you can drive around normal and never use the turbo, and climb in the gas and spool the turbo up, what you are noticing is called turbo lag, which is the biggest down fall when compaired to superchargers!

Its eather the gauge or sending unit. On a single wire unit,if you ground the wire ,the gauge will max out.This means the unit is bad. I hope this helps.

1987 non-turbo: 10 deg Before Top Dead Center (BTDC) @700 rpm
1987 Turbo: 10 deg BTDC @650 rpm.

To set the timing, you will need to connect a jumper wire between terminals E1 and TE1 on the diagnostic terminal. This diagnostic terminal is located just aft of the engine compartment fuse box. It is a black plastic box marked "diagnostic" on the cover, which flips open to reveal the terminals inside. There is a diagram on the inside of the cover which explains the terminal positions. On the Turbo model, you need to remove the forward section of the engine cover to gain access to the number one spark plug wire.

It sounds like your cooling fans are not comming on by themselves, but when you turn on the ac it forces them to turn on. Make sure relay is good, then replace coolant temp sensor, this may have failed no telling pcm to turn on cooling fans. Thanks

is the temp gauge sender new
or the engine cooling fans spinning fast enough
air in the heating pipes ? bleeding

Check to make sure your thermostat works right by monitoring the warming up of your engine. With a completely cold engine, start and run the engine for a few minutes, then put your hand on the top radiator hose to monitor if and when it gets warm as the thermostat opens more and more and note the gauge reading( if it works) the top radiator hose should be unbearably hot within 5-8 minutes. If the therm. opens right it should close right aswell, staying open a little while eventhough the radiator may have cooled may be what you are experiencing causing the rapid cooling and is nothing to worry about. The Hose should not get warm very soon after starting the engine. Regarding you gauge, lets take one step at a time, verify proper op. or the therm.