thermostat

T

tee

Member
Had some issues with overheating so i decided to change the thermostat and see what happened.....the one that was already in the car was rated at 65 ish degrees, and the replacement one was 76.5degrees.

After i changed the thermostat the car was fine, though there was a slight leak from the housing as i think i didn't let the sealant set before i started it up.
So opened it up again and refitted as before.....now car overheats again.

Now i have just recently changed the water pump, and have got an uprated copper core radiator with twin fans that are wired constant with the ignition.

So i decided to try running without a thermostat in at all, and it runs fine......

Now before fitting the thermostat i got the new one, the one that was in the car, and another spare one and put them in hot water....they all opened and then closed when removed from the water. Although the one that was originally in the car seemed to open a bit slower and close slower also.

So i am now thinking that the one originally in the car only recently started to overheat, so was maybe on the way out.....and the replacement one is rated too hot and so is causing it to overheat.

So i guess my question is should i get a 65ish degree thermostat (rated the same as the original one) and fit that? And if so where would i get one from? AFAIK i was told it was an uprated NISMO item

Sorry for such a long winded post but just wanted to give as much detail as possible :roll:
 
J

jambo_gtir

Member
The NISMO ones open sooner.... I had one in mine and even in the summer, the cooling system was too good and oil temps stuggled to creep up.
How do you know it's overheating? The coolant temp gauge will not be working properly if you have an air lock.
I take it when you keep opening the stat housing and swopping stats, you bleed the system again each time?
 
T

tee

Member
been spending ages bleeding out the system each time yes.....
at the moment there is definitely no air lock and the temp gauge doesn't go much above about 1/4.

so any ideas on where to get a replacement NISMO one?
 
splmum

splmum

Active Member
tee said:
been spending ages bleeding out the system each time yes.....
at the moment there is definitely no air lock and the temp gauge doesn't go much above about 1/4.

so any ideas on where to get a replacement NISMO one?
Click to expand...
Why are you worrying about the gauge not going much above 1/4, mine sits permanently at about 1/3.
If your gauge was reading not less then 3/4 then there might be a problem.

As you are using a Nismo 65degrees thermo you will be getting water through it a lot faster and cooler that the standard 76.5degree unit, which is what I am using.

Or am I mis-reading understanding what is the problem.
 
T

tee

Member
well car started to overheat with the nismo stat in, gauge was going to about 3/4, so i changed the stat for a 76.5, that was still overheating but worse.
so am now running no stat and car is fine, but i need to put a stat back in at some point no?
 
GTIR1000

GTIR1000

Member
i dont think its a good idea to run with out a thermostat for ever here is a quote from bob himself i found on another thermostat thread. Although i did run one of my old r's wth out one for a few years with no problem so i suppose its up to you:)

"do not run car without a stat fitted....people think that its just for heating the coolant system quicker which is not the case.
the stat effectively holds up the water flow in the rad long enough for it to be cooled, by removing it altogether the water will then flow too quickly and will not get cooled sufficiently, this then has a knock on effect and the coolant will gradually get hotter and hotter and eventually lead to a boil up"
 
T

tee

Member
i would have thought the stat is needed, but what i need to no is, where can i get another one of the lower temp stats from?
 
splmum

splmum

Active Member
tee said:
well car started to overheat with the nismo stat in, gauge was going to about 3/4, so i changed the stat for a 76.5, that was still overheating but worse.
so am now running no stat and car is fine, but i need to put a stat back in at some point no?
Click to expand...
From this statement I don't think it is either of the thermostats that are buggered, sounds to me they are both doing their respective jobs.
But, having said that, you do have a problem, I can't say what is is but the cheapest way to start the elimination process is to chuck out your old radiator cap and replace it, put back in the 76.5degree thermo and see what happens.
If your temp is still 'boiling' then you possibly have something else causing your problem and will need somebody who knows cooling systems to decipher the cause.
 
T

tee

Member
ok coolio will try the rad cap and put back in another 76.5 degree thermostat.

this is a really dumb question, but what does the radiator cap have to do with it? apart from stop the rad water pouring out?
 
PobodY

PobodY

Moderators
Staff member
splmum said:
Oh dear!

It pressurises the cooling system.
Click to expand...
...which makes it like the lid on a pressure cooker. - You get an increase in the boiling point of the water that way.
If it doesn't open and vent when it reaches 0.9bar (for a standard cap; you might be running a 1.2 or 1.3 bar cap) the pressure will keep rising and the coolant will keep getting hotter... until it finds a way to get the pressure out.

Similarly if it's opening too early the coolant will keep boiling out into the reservoir.
 
Fast Guy

Fast Guy

Moderators
Staff member
Do you have any leaks you don't know about? Biggest clue normally is you can heard the cooling system making noises after shut down when it's low on coolant.
There's not much that will cause you to overheat: water pump, thermostat, knackered rad, low level due to leaks, blockage. Cracked head, block and head gasket will probably cause bigger issues.
 
PobodY

PobodY

Moderators
Staff member
That would be my concern too; a pinhole leak in the head gasket letting hot exhaust gas into the cooling system thus causing constant overheating.
 
D

danr

Member
its not the dash temp sender faulty is it? can you hook consult up to read the water temp from that?

thought i'd try the obvious jic..
 
T

tee

Member
i've got a 1.2 bar radiator cap fitted on it......
im gonna try putting back the thermostat now and see what happens, as i got another 76.5degree one today

tbh i don't think its the gauge sensor, tho i do have a replacement on the way so will probably change that at some point.
 
PobodY

PobodY

Moderators
Staff member
So you're running it at about 30% over pressure... that might account for the increase in the reading on the gauge.
 
P

pulsarboby

Guest
ive put you both the temp sensors in your package as you never stated which one you wanted;-)
those and the hub were collected today so may be with you tomorrow hopefully
 
PobodY

PobodY

Moderators
Staff member
Well it's technically 0.9kg/cm2 (which is 0.88 bar), but anything between 0.8-1.0 kg/cm2 is considered good for the standard cap.
 
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