need help......quick engine question!!!!

[rhodog77]

Can someone verify what this is and what it does. I have a small problem and I think this might be the main issue...long story!!!!

thanks a ton

[lo72]

Looks like a temperature sensor, they are usually in the head to get a true temp reading. They go to the gauge or temp light. Greg
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[rhodog77]

well thats what I thought as well. I placed my temp sending unit is the same location but something is not right. I have matching gauges and sending units but I think its not reading right. My gauge is working but I think its reading incorrect. When the guage reads 225, i checked the water jacket, rad hose and block with an infared therm gun it reads 185. I had troubles with a temp sender for my fan relay as well. I think this might be the issue. I think I will place the gauge sender in the intake and see what happens.

thanks for the quick response.

[lo72]

No problem hope ya get it worked out. Are you using any kind of sealer on the thread? Some times that will screw with the readings.
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[rhodog77]

no thread on either the gauge sender or the relay sender. I was going to place the relay sensor in the block as well but I couldnt find another access point. So i think I will place the gauge sender in the intake as well. I have the fan wired to a switch now but would love to get the relay working.

thanks again

[entourageguy]

the head will read different than the manifold but I can't remember which is higher.

[rhodog77]

my head temp is higher than the intake, Im going after this little problem tomorrow.

thanks for the info

[mr48chev]

I've seen some aftermarket electrical gauges have readings way off the mark before. The worse was a new highly respected brand on my buddy's Model A ford with a Chev V8 in it. It read about 100 degrees high.

That spot on the head is the normal position for the temp sender on small block Chev engines though .

One thought. Is the body grounded to the engine properly?

[OrrieG]

When I moved my sender from the intake manifold to that head location is read 12-15 degrees hotter. I assumed it was because the water was closer to the combustition and heat associated with the pistons, etc. I have been doing some research on emission Q-jet carbs and remember that there may also be some emission sensors that go in that location to.

[T Hilde]

I am getting ready to do the wiring on my rig. From what I have read the fan sensor should go in the head and the gauge sender in the intake. I think it was for the reasons Orrie said.

[rhodog77]

hey guys,
thanks for all the info. I got the block drained this morning and removed my temp gauge sender from the block and up to the intake. I also re-installed my temp relay switch for my fan in the intake. I really wanted to have both sending units in the same location. I hooked the temp gauge sender back up and now its reading much closer to what my temp gun says. I think that this was the way to go IMO. The reading when it was in the block was way to high. Im going to rewire my fan relay now to see if i can get it to kick on.

Thanks again.

[55metalmonkey]

Originally Posted by mr48chev

I've seen some aftermarket electrical gauges have readings way off the mark before. The worse was a new highly respected brand on my buddy's Model A ford with a Chev V8 in it. It read about 100 degrees high.

That spot on the head is the normal position for the temp sender on small block Chev engines though .

One thought. Is the body grounded to the engine properly?

Dotto on the ground, I never rely on the head bolts as the ground for the head. I usually put a ground strap from the block to each head on the back by the fire wall. it's not always nessasary but couldn't hurt. poor grounds make strange things happen

[solidaxel]

I have found the passenger head to be a bit cooler than the drivers side head 10* +/_.

I have also found that I need the relay switch (ground for relay) sending unit to be 15-20* HIGHER than the thermostat, with the gauge sending unit next to the outlet in the manifold.

I can calculate from these positions how the engine is performing with the outside ambient temps.

Down here in the summer you don't have the fan in the off position very often with a 200* swith"

Make sure you have all of the air pockets "burped" from your cooling system as steam will read 15-20* higher than plain water.
Cycle your cooling system several times with a catch can to make sure you are filling the voids in the system, maybe even over night 2 or 3 times before you make any great changes.
You should be able to start the fan with a cold engine (key on) by just touching the connection at the ground switch with a jumper from there to the block or a known ground.

[wildearp]

It makes more sense to put the sensor for the fan in the radiator, if you have a fitting for it.

[wildearp]

As far as accurate gauges, Autometer's racing series gauges use a permanently attached pickup with a nitrogen filled capillary tube to the gauge in the dash. It would be hard to find a more accurate or faster reading gauge on the market. If you have a lot of money in your engine, it is good to use the best temp gauge that money can buy.