96 Bronco Spikes Temp Guage

[IdahoSpud]

Okay boys,

First of all nice forum. I have a couple and know where to find info I can't figure out. Here it is and lets see what you think. I am out of ideas.

A customer brought in a 96 for Bronco with a 5.8, the issue is that at idle the truck is fine. But the ECT sending unit guage will spike. Like 90% and then go back down to half.

The Data port on the scanner says 156-175 when it does this.

So I checked the guage by grounding the wire and if went full, did this a couple times.

Water flow in radiator is flowing well, it was brought into me after the heads were done. The guy said it overheated and quit. I am unsure if this was the safety shutdown for the head temp or not.

It has a new water pump on it. It doesn't look like a motorcraft or any name brand I am used to seeing.

I took readings with a infared and the head temps never went above 180 even when the guage spiked.

I installed a mechanical sun pro temp gauge to see if that was it. Nope.

The sun pro will sit at idle about 190 which Is good. Then it will spike to 215-230 and then go back down.. to 190 and continue to do this.

The truck has some lifter noise even after this customer got the truck back from the guy who did the heads for him. But it goes away after about 10 minutes of running. This motor only has less than 100 miles on it since the heads were done.

So since all I did was rant.. this is what I have replaced.

1) ECT

2) ECT sending unit.

3) New motorcraft Thermostat

4) Removed the sending unit and installed a mechanical temp guage. (tonight) still spikes

Other than the spike on the temp it runs pretty good. Flew through smog.

This truck doesn't have any special burb procedure does it? I mean it is still a pretty basic system. I don't think the water pump could be doing this?

The top radiator was averaging about 140 and the bottom was 120-130. The thermostat housing stayed pretty close to the scanner readings about 170-190 even when the dash gauge and the mechanical aftermarket guage spiked. The scanner did not spike?

Confused ? I am

Thanks again for any input.. I will check tomorrow.. when I get to go try and fix this beast..

Nothing I can find on IATN or Identifix..

Spud

 

[rednck7736]

By any chance did the shop that done the heads may have put one of the head gaskets on backwards.Both the large water ports in the gasket must be to teh back of the head.I did this once many years ago before I new better and my truck wanted to run hot pulling a load and sitting and idelling it would jump up above 190 and once u dronve it it would go back down.

 

[IdahoSpud]

Yes true mechanical guage. The spike is only showing on the guage from the sending unit, then to this guage. And yes sorry about not being to specific. I replaced the sending unit next to the distributor, and installed the mechanical guage in its place.

It does not show on the scanner which is monitoring the ECT correct?

I am trying to burp the system with the front raised and the heater on this morning.

Thanks for the input. I will let you know what turns up..

Spud

 

[IdahoSpud]

Correct,
ECT no spike. And the stock and Sunpro "did" I have it raised in the front, cap off and heater on. And it has been running for a half hour. It hasn't spiked this morning at idle. And it did last night? Will let you know.

Thanks for the help.. And I will read those Bull's.

Thanks again Guys..

BTW: The scanner says 165-170 but the sunpro says 210 just a little more info.. thermostat opens fully at 210-215 so what would be a good operating condition.

 

[IdahoSpud]

BTW: The scanner says 165-170 but the sunpro says 210 just a little more info.. thermostat opens fully at 210-215 so what would be a good operating condition.

UPDATE: I replaced the fan clutch because it was free spinning a little to much at the higher temps. It reduced the vibration I was feeling quite a bit.

Also I removed the thermostat all together and now it doesn't spike. It stays at 150-170 when it idles. But this can not be a good operation temp for the vehicle can it.?

I cannot find a 160 thermostat for this truck to try it. But the motorcraft 190 was just getting it to hot.

The truck is a 96 ford bronco with a 5.8

So the temp guage doesn't spike anymore with the thermostat completly out. Let me know what you think I should do from here. I dont want to let this go if it is going to cause this guy any worries.

Spud

 

[Yardape]

Have you tried it with the new fan clutch with the thermostat in?