Low torque on one head stud - Toyota Nation Forum : Toyota Car and Truck Forums

dlf60 · 01-21-2006, 09:50 AM

I am having a coolant flow issue on my 89 Supra turbo. I have no flow with the thermostat installed as well as no movement of the coolant gauge. I have determined that I have flow without the thermostat installed and have replaced the gauge sender (I neglected to check for gauge movement with the thermostat removed) I was told that loose head bolts or studs might cause gases to escape from the combustion chamber and disrupt coolant flow. All of the ARP head stud nuts are torqued to 80 ft. lbs. except the second one back on the intake side of the head. We estimated that one at 65 ft.lbs. and were unable to torque any further as the socket was slipping off the nut. Could this be causing the coolant flow problems and if so , could I retorque this nut or remove/replace it and torque it without causing damage to the head/gasket? ( I mean just that one nut, without loosening/retorquing the other nuts)
Thank you

Jeeves · 01-21-2006, 12:23 PM

To have NO flow via that method, you'd have to be dumping ALL your coolant into that cylinder and we all know that's not happening. What happens if you remove the thermostat? Also note, it's very easy to swap two of the wires on the thermostat housing and then your gauge won't read at all.

dlf60 · 01-22-2006, 03:11 PM

The green and yellow wire (which is the right wire per the factory wiring diagram)is going to the gauge sender (wide flat blade connection) Just to make sure, I ordered a new sensor from Toyota and replaced it with no change. I have grounded the green/yel wire and got a gauge deflection. I have verified voltage present at the connector to the sensor and continuity from the sender body to battery ground. With the thermostat removed, the coolant initially appeared to flow, then stopped. Some time later air was forced out of the system (saw bubbles and coolant was forced out of the radiator). It appeared to be flowing again after that. The car idled for 25 minutes and the water temp did not exceed 130 deg. F. There was no deflection of the coolant temp gauge during this time. Thanks for your help and patience Jeeves.

Jeeves · 01-23-2006, 12:18 PM

There are two flat blade connections. One will make the gauge work, one will cause it to never work. On mine, I accidentally swapped 'em and got nothing. reversed it and they worked.

dlf60 · 01-25-2006, 05:31 PM

The coolant temp gauge is now working. When I changed the sending unit, I had the wires reversed. I removed butt connectors from both wires and soldered in new wire. After running for 20 minutes (no thermostat installed) the temp gauge was at about 1/4 scale. Thanks Jeeves! Can I tighten the one head stud nut that I think is at a lower torque value (65 ft. lbs. as opposed to 80 ft. lbs.) alone and do no damage to the head or do I have to loosen them all and start all over again? Would it be better to just leave it as is? Thanks for your help!

Jeeves · 01-25-2006, 06:57 PM

That's a toughie.

In sticking by the book I'd say that it'd be best to break them all loose a 1/4 turn, then torque them all down to the setting you want over two or three passes including that nut that was looser than the rest. In this way you're doing a full retorque (be sure that you're going through the de-torquing sequence in reverse) and you'll know nothing's awry.

However, the lazy person in me says "Just loosen that one 1/4 turn, then torque it down."

It all depends on how 'well' and how much effort you want to put into it. For all we know, the effect could be the exact same either way.

[img]http://www.**********s.com/supra/torquing.gif[/img]