overheating problem (and some questions)

[btoran]

my car has been running hot recently and my temp gauge doesn't seem to work well. For example, it reads about 140 but the top of the block is 175 (measured with a heat gun) while the bottom is 145. i now have a replacement temp sending unit, but not a deep enough socket. does anyone know what size socket it takes?

i tested the wires going to the radiator fan and i have 12v and the switch was recently working.

so, where do i look next?

should i first test the thermostat (and where would an internal vs external thermostat be hiding?), the radiator (not even sure how to check one of these), or something else?

[spidernut]

The motor will run right between about 185 and 190 degrees and the fan will not turn on until the motor is about 195-198 degrees. As long as you're running under 190 you're doing fine.

Let your car idle for about 15-20 minutes and see if the fan turns on prior to the 200 degree mark. If it does, your fan is working properly. If it doesn't turn on after about 210 then you may have a bad fan temp switch at the bottom of the radiator.

[btoran]

thanks. i'll do that test tonight. a few more questions....

1. does the thermal switch at the bottom of the radiator also sense the temperature, or does it simply turn on/off based on the temperature of the temp sending unit located between the heads (on top of the engine)?

2. what size socket do i need to remove and replace the temp sending unit on the top of the engine? i don't have a deep enough socket to even know the size.

3. should there be a big difference in temps between the top and bottom of the radiator?

[chrisfiat]

the rad fan sensor is self contained and does not rely on the guage sensor, short the two wires in the sensor to test fan
don'k know the socket size, but probably 22 to 24 mm

yes there should be a big difference between upper and lower radiator, otherwise it would not be working and just be a hot water tank, it is designed to shed heat, but remember it must have flowing water and air moving across it to work properly, so if it sits and idles (ie no moving air till the fan comes on) the lower portion will show less of a differential in temp from the upper portion, hence the reason the fan sensor is in the lower tank

[paintdudeluke]

the sending units on the head are only for the gauges. I swapped em out for a mechanical gauge in mine. Without a fan running it will do the slow climb while sitting at lights. Your thermostat could be sticking closed if it has temp issues. Its a t-coupler on the pass side between (connecting)the hoses.

[paintdudeluke]

diag questions:

1) does it boil over or just seem warmer than normal? if yes, how quickly and under what circumstances.
2) does it lose water?
3) how fast does it get "hot" when you fist start it up, does it go straight to overheat?
4)does your heater work?
5) hotwire your fan straight to power. Does it work?

Answer these and isolating the problem gets easier.

[4uall]

Here's where mine was hiding I had both internal and external



This might help

http://wwwe.fiatspider.com/f08/viewtopi ... verheating

[btoran]

Jay - Thanks. I was hoping you would chime in with a "This might help " link.

[btoran]

paintdudeluke- is the "external" t-stat inside the part you pictured below (and can be removed) or is it the whole part you pictured?

[ScotcH]

paintdudeluke- is the "external" t-stat inside the part you pictured below (and can be removed) or is it the whole part you pictured?

It's a complete unit

[4uall]

This might help again

item 22 on 2nd pic



http://www.youtube.com/watch?v=m5Xnrfjc9qU

http://www.scuderiaitaliancarclub.asn.au/tech.htm

[btoran]

it does. thanks again. in reading your previous link, i'll check to see if i have an internal t-stat as well, but i doubt it.

you wouldn't happen to have a linky telling the correct socket size for the temp sending unti that sits between the heads, would you?

[4uall]

Sadly, I do not. Someone reading this should be able to just go out and try some sockets and report back. I am at work and Fiona is at home, otherwise I would have done it already

[paintdudeluke]

internal and external? I didn't know they came with internals at all, I assumed they were all like mine.

[btoran]

i didn't realize there could be two either, but apparently some cars are setup that way (incorrectly, i believe). my cooling system was working until recently, so i don't think that's the problem, but i'll check any way.

a question about testing the radiator fan switch. if the fan does not come on when the car is hot enough, the switch might be ok but the fan itself bad. how can i bypass the switch to test the fan itself? can i use a single wire to jumper across the fan switch terminals (or across somewhere else)?