Engine Temp Question

[pcf_mark]

Odd thing has started with my 5.0 roller engine when I swapped it for the 289. When I did this swap and put a new 195 thermostat in so I know it is 195 (says so anyway). I also did the serp. conversion at the same time. With my 289 and the 195 the temp would hit 195 and sit no matter how hot or cold, sitting still or driving. Super stable. I have the sensor in the thermostat housing.

With the 5.0 and serp set up my engine barely gets to 140 sitting still. Today I blocked part of the radiator and let it idle for 10 minutes. It hit 195. I jump in and drive down the road. Temp drops right back down to 140-150 range.

Something does not seem right. I am wondering if I have some air and maybe it comes to the highest point so it fools the sensor? I have not checked what my EFI thinks the temp is - that is a different sensor in the manifold. Or is the Explorer fan and shroud mod so awesome that I am getting over cooled?

Thanks fellas

 

[Timmy390]

If the stat is 195 it sure as heck shouldn't be running 140ish even with the Explorer serp. My guess is, either the stat is hung open, you got a bad stat from the parts store or the temp sensor is bad i.e. reading wrong.

I had a bad sensor on my brand X full size pickup a few years back. It would never get up to temp per the gauge and the ECM was freaking out because it was getting a reading of too cool when other aspects of the engine data showed it shouldn't be cool. I replaced the sensor and all was well.

Do you have a thermometer gun? I use them all the time to check temps. You can use it to check the temp at the stat housing and then you know if the temp is right or wrong. I have a cheap HF temp gun and it's awesome. I use it when doing maint on my outboard. I can quickly see how hot each cylinder is getting and when the stats open.

Tim

 

[Seventee]

It's all too common to get a bum parts house T-stat. I try to only run Motorcraft or a quality aftermarket brand.

As suggested, try the thermo gun, it's an easy way to check without pulling your hair out.

 

[brianstrange]

Bad engine ground, or too much Teflon tape around the sensor can cause that as well.

 

[surfer-b]

Like others stated. The temp sensor, you need to use the OE from the 289 or one that is calibrated for the Bronco gauge

 

[savage]

I agree with everyone on making sure you have the right temp sender.I run a 180 thermal and it runs around that temp give or take depending on temp out side.

 

[pcf_mark]

The sensor is a carry over from the 289 so I had not considered it. It have a wrap of teflon tape but just 1 1/2 turns. Let me see if I can see what my EFI sensor is reading that should tell me if I have a bad t-stat or a bad sensor. Thanks fellas.

 

[Broncobowsher]

The fact you can get to 195 by blocking the radiator shows that the temp sensor is working right. IF it was reading low due to bad ground you would have really cooked the engine when you did the blocked airflow test.

Go get the thermostat from the 289 (that worked) and put that into the engine that runs cold.

 

[pcf_mark]

Ok I replaced the t-stat with a new Stant 195. I had to do this anyway because I had a leak at the t-stat housing so I swapped it. With the engine idling for 10 minutes or so the temp gauge reads 170.

When I hook up my laptop the EFI temp gauge says 195. This tells me the engine is really at 195.

The EFI sensor is in the intake on the front left near the t-stat housing opposite the heater outlet. The gauge sensor I have at the back of the intake manifold near the firewall. The EFI intake (95 vintage) did not have a sensor back here (no cross over passage either) so I drilled and tapped it.

Now I am wondering if it is cooler back there which seems impossible or the water getting to the sensor is not from around the bores and chambers but maybe just cruising along the top of the engine.

When I have time I am going to move the sensor back to the t-stat housing like it was on my 289 to see if it reads the same as the EFI.

Kind of weird but wanted to share that for the curious among you.

 

[Viperwolf1]

It is cooler at the rear of the intake because the coolant hasn't flowed through the heads at that point. It's probably reading the correct temp for that location.

 

[pcf_mark]

Interesting I was not sure how the water flowed through the engine. Good news is I fixed a leak and found the upper hose was rubbing through so all good. Thanks!