blandis

1996 3.4

Just replaced head gaskets on 1996 3.4 5vzfe. All went together well and runs fine. Used all Toyota parts.

Temp gauge does not work. Follow the FSM and did the coolant temp senor ohm test, was withing spec at all temperature ranges. Unplugged the sensor triggered the check engine light. Gauge worked before I tore it down. At this point I am thinking maybe a break in the wire between the sensor and the gauge. Is there a common place where these break? Anything else I should check?

Truck did not overheat prior to me tearing it down. Now that is it back together, Top of radiator gets warm, as well as the top hose. Bottom hose is cold as well as the bottom of the radiator. Thermostat opens up, did the boil test. Want to thank my wife for allowing me to use one of her "old" sauce pans. Does not seem to overheat, had a few temp probes to check, when thermostat is left in it.

Drained radiator. Dumped water in the radiator and it runs out the drain. Removed thermostat. Run truck and coolant flows through the radiator. Tells me it is not plugged. Bottom hose will get hot when thermostat is out and you let it warm up.

Does not seem to be overheating with thermostat in or out. Could I have airpockets? Filled the top hose first. Left cap off when we started it.
Could us running it without the thermostat have eliminated any air pockets? I have not put thermostat back in after running it without thermostat. That is my next step on Monday.

rworegon

You are checking the gauge temp sender near the fire wall on the driver side of the lower intake manifold? It has a single wire going to it that feeds the dash gauge.

HighLux

you have air in the system. you need to burp the system and get the air out.

yodafan93

X2 what highlux said.

Bigblock

Just pull off a heater hose to let the air out. As far as the rad being cold on bottom,sounds like its doing its job.

blandis

Will pull the heater hose and try that.

I was only checking it at the sensor. Very well could be the single wire is not hooked up as I did not check that. Where/what color is the single wire that feeds the gauge.

Appreciate the help.

rworegon

Likely it's yellow with a red stripped wire between the back of the engine and the firewall slightly to driver side of center.

You can see the temp sender threads into the lower intake manifold. See pics in post 12 here. It's the bright spade between the two blue taped off tubes in the first pic. The wire should be in the area if not hooked up.

blandis

Thank. I can tell you I have not even looked in that area. Sure wire it hiding somewhere back there.

I have been trouble shooting the sender up front. This is why I love forums!

I will report back Monday night.

rworegon

ECT sensor up front only 'talks' to the ECM computer. The one in back 'talks' to the temp gauge on the dash.

When you change out the t-stat (or put it back it) fill the block though the upper radiator hose...this helps to fully fill the block before the t-stat opens.

DRCOFFEE

When you replaced the t-stat, did you put the jiggler in the 12 or 6 o'clock position?

rworegon

For the 3.4, the FSM calls for jiggler in the 6 o'clock position.

blandis

I put it at 12. Manual says 15 degrees on either side of 12. Seems like most have better luck at 6.

rworegon

Switch it to the 6 o'clock position. What manual are you using? I'd not be surprised if the Haynes, Chiltons, etc. have a conflict with the Toyota FSMs for the 3.4L.

DRCOFFEE

I thought that might be the issue. everyone who has put t at 12 has this problem. You need to change it to 6 o'clock

kball

You should use that manual for kindling...

blandis

Thanks a ton. Wire connected and temp gauge works. I went over the whole engine bay 3 times prior to hooking battery up. Missed that one. Clip was pinned under the plastic harness, had to dig a little for it. Installed jiggler at 6.

Drove it home tonight (12 miles) and all seems well. Just its maiden voyage. Will watch everything closely for a while.

rworegon

Glad you found the wire and moved the jiggler to the 6 position.
It's a great feeling to do the work, do the debugging, and then enjoy the rig again.