The Dodge Challenger Message Board

Hi
I look for your oppinion guys. I have mounted a sender unit to control my electric fan a while ago. I choosed a model from a toyota because i liked the small shape (M16 x 1,5) and the temp seemed to fit my needs. It was supposed to have 92 C- 85 C (197 F- 185 F) i am so bored out now because it will not be accurate.
The first i tried did not give signal until the water boiled, and stopped very soon (short signal to fan)
So i tested it in water with a temp sensor. It gave signal at 101 C - 97 C (213F- 206F) I bought another one, and it was nearly the same... These two was supposed to have the signal area about 95-88 C (203-190F)
I got a bit depressed since i already had welded in a nut in the radiator, but found the sensor with a bit lower range, i tried 3(!) and the best gave signal at 97 and dropped signal at 90 (206-194F) I am using this sensor for the moment. My plan was to get a overflow tank to my radiator, but for the moment i have a 16psi cap. But still i feel this is to close to boiling point...

What can you guys suggest? Will this be safe? The fan is really realible/ effective. I thought maybe this sensor will due if i get a overflow tank, because that should do that the water do not boil at 100C (212F) but if i do not, is it enough to have the 16psi cap...?
Or should i try to install another sensor with more accuracy, and weld another nut if necessary... (please not)



(I have placed the sensor near the top of the radiator because of the range the sensor is supposed to have)
But the sensors are tested in water indoors before i ever mounted them. So trust my numbers...

Also... i may have been thinking wrong installing the 16 psi cap. Will this help increase the boiling point(?) Or just keeping the preassure for a longer time? My plan was to have a 13psi cap with a owerflove bottle, but thought this could be a way out for the moment... Maybe it is a bad idea using this cap. Correct me if i am thinking wrong here guys??

I use regular thermostat about 85 or 88 i think 185 or 190 F

First.

Rather than fit an overflow tank fit an expansion tank so that water is sucked back into the radiator as it cools and keeps the radiator completely full at all times.

Second.

A 15 or 16 psi cap is fine. Use a modern one that will allow for the expansion tank.

Third.

Idealy you want the fans to come on at 185F and off at 170F.

You do not want the temp to ever go over 190F if possible. That way you have some headroom for that one day where you are stuck in a traffic jam and the outside air temp is 95F.

Painless do a thermostat switch that screws into the radiator, engine block or water pump. I have this one;

http://www.painlessperformance.com/webc ... ield=30103

They also do an adjustable version that allows you to fine tune the on-off temps;

http://www.painlessperformance.com/webc ... ield=30104

Thanks Dave. I feel the temp should depend on where the sender are placed. Where have you mounted your's? I thought this from painless might suit best in the lower part of the radiator? I have a stock radiator, so no tubes for the water to return...(?) Is it meant to have some special cap to combine with a tank(?) I have no clue how to determine if the cap are made for a tank(?) It is a new cap from Mr Gasket...
Do you think it is enough to have a 16psi cap and no tank?
I thought because i have a stock radiator the only way to go is a 13psi cap and an overflow tank, like these maybe? http://store.summitracing.com/compare.a ... toview=sku
They told me the other pipe do not need to be connected to the radiator..
Tell me what you think, i appreachiate it.

I don't have a heater in my car so I screwed the fan thermostat into the water pump housing where the hot water outlet would go.

This gives me the temp of the actual engine block which is what you want really.

An alternative would be the radiator close to the top hose as this is where the hot water enters the radiator from the block. But to work correctly there you need the radiator completely full.

You can make an expansion tank easily.

All radiators have an overflow outlet at the cap neck.
All you need is a plastic bottle such as the cheap catch cans sold by Summit Racing and Moroso. They have a little tap on the bottom you can open to drain water out.

All you need to do is to fit a bit of brake pipe to the top of the bottle that runs down to within a inch of the bottom of the bottle. Attatch the overfow pipe to that.

What happens is that as the water expands it fills the bottle. As it cools and contracts it will suck the water up the bit of brake pipe and back into the radiator.

Your cap will probably allow this. Most modern caps do as modern cars have expansion bottles.

One of these will work.

http://store.summitracing.com/partdetai ... toview=sku

Just fix a bit of brake pipe to run from the top down the inside. Cheap way to do it.

Or you can get an expensive aluminium one.

Sorry Dave, the link i posted is to caps that are very simular to mine, i do not remember part number. But they look almost like those in the link.
I was really about to post a link to some TANKS It went wrong.. here you go:
http://cgi.ebay.com/ebaymotors/ws/eBayI ... 0182455945
Do you think one of these would work out?

I have placed mine close to the upper house in the radiator. Should it be better with 13psi cap with tank? I have started to worrie a bit with the 16 psi cap, if the houses etc will keep intact with higher preassure, since i am running the radiator so full... Am i thinking wrong here?

http://store.summitracing.com/partdetai ... toview=sku
Cap looks like this, but 16psi

Jimiboy wrote:http://store.summitracing.com/partdetail.asp?autofilter=1&part=MRG%2D2470S&N=700+115&autoview=sku
Cap looks like this, but 16psi

I have one of those. Not tried it yet to see if it works with the expansion tank. But don't worry about the 16psi. that is fine.

The steel tanks you linked to are overflow tanks and not expansion tanks. They probably have no internat tube but it is impossible to tell for sure.
You want a tank with an inlet at the top that runs down to the bottom of the tank.

Thanks for helping out. The overflow tank i posted will not suck the water back then?

Jimiboy wrote:Thanks for helping out. The overflow tank i posted will not suck the water back then?

Does it have a pipe that goes from the top to the bottom?
If not then no it is no good. The water has to siphon back out.

I asked if it work like a overflow can or expansion tank, and if it will suck back the water, this is how they replied: "There is a pipe that stick up inside, that tube is to empty the tank if it overflows. and yes it will suck back to the radiator when it cools." Tell me what you think Dave... I like the look, and it should fit beside the radiator.. But i do want it to work of course..

How much water it sucks back into the radiator depends on how long the internal part of the pipe is. It can only suck water if it is submerged in it.

You also want to maintain an overflow because you don't want the can to fill completely and if your engine did boil it is better to blow steam out of the catch can than out of the radiator core if she blows!

I feel like this is hard english reading for the moment, but they told me this... "The second hose is for the overflow of the tank it self in case it gets full" Should i ask about the pipe inside?

If that twist cap sits at the top then it must have two pipes at the bottom for a reason. It probably functions as an expansion tank as well.

If it goes that way up (cap at the top) then you will need to connect the overflow from the radiator to the short pipe. Then the long pipe will get rid of any excess water in the can.

Go for it!