Renewed cooling system -- now it's running hot?

[Brendan-s]

Okay in prep for Fraser Island in August I've just completely redone the cooling system. Brand new radiator, new water pump, new thermostat, new hoses and clamps, good Nulon coolant.

Finally finished putting it all together tonight, flushed it with a treatment, ran that for 10 min, dropped it, then twice filled and flushed with fresh water before putting the coolant in. Problem now is that under hard load the engine temperature climbs - I'm only going on the stock guage but it gets up to 2/3 quickly.

The radiator is doing its job perfectly as the top tank is bloody hot and the bottom is cold enough to hold when its running. The only thing I can think of is that maybe the thermostat isn't the right one? Not sure what temperature it opens at but I had the option of a standard or hi-flow, and seeing as the entire engine and everything's stock I figured standard was the way to go.

Any suggestions on what might be happening. Gonna go and make sure the fan belt is tight enough and maybe put the old thermostat back in but apart from that I'm stumped??

[suzimad]

stupid question , but did you put the fan back on the right way ? eg the ribs in the middle where the bolts go to the front of the car ?

[Brendan-s]

Pretty sure I did, the inside of the fan had a mark from where the spacer block that goes between it and the pump had been sitting so its on the right way.

I just went down to have another look, and figured I'd let it idle for a bit while I changed a wheel over (leaky bead). After 5 minutes it was at 2/3 temp -- the needle was sitting dead flat horizontal.

One other thing I forgot to mention. When filling it back up with coolant it was sitting flat. Today someone mentioned that it should have been facing uphill to help get any air pockets out. I did idle it with the cap off for about 5 minutes while I kept filling it and it definitely wasn't bubbling when I put the cap back on (new recovery cap). Is it worth draining and refilling it in case it has air in the system?

[zook4fun]

i'd be checking that you put the thermostat in the right way. its got me before when i didn't look at it right.

turn you heater on full and run for a few minutes as well

[Brendan-s]

That's definitely in the right way too, with the bleed valve towards the front of the car. I might go put the old one back in when it all cools down and see how that goes unless someone has a better suggestion?

[Dozoor]

That's definitely in the right way too, with the bleed valve towards the front of the car. I might go put the old one back in when it all cools down and see how that goes unless someone has a better suggestion?

good idea.

[suzimad]

the best way to bleed air out is to to take the hose closest to the r/h hand guard on the auto choke off and fill the radiator till no air bubbles come out that hose (you will need to drop the hose below the manifold level for it to run out) , this is the highest point in the cooling system.

if the gauge needle is staying horizontal and not rising above this point while idling (when airflow through the radiator is at it lowest) or when driving (where airflow over the radiator is its greatest) i would seriously not worry about it , it probably means that things are working fine.

if it was too cold there is issues with the auto choke not coming completely off.

in your first post you said the temp climbs high under load , does it get over the horizontal mark on the gauge ? if that were the case id say you had a blocked radiator or airflow issue , or the thermostat was not opening fully.

you have confirmed the fan is on the correct way and that it is a new radiator and thermostat.

maybe do a test drive in 4x4 where in most cases your cooling system will get its hottest and report back.

[Brendan-s]

Hmm well I pulled the thermostat but couldn't find the old one (must have chucked it) so tomorrow I guess I'll try and get a high flow one and see if that helps.

The needle was sitting on horizontal at idle with obviously bugger all airflow, but that isn't halfway -- it's more like 2/3+ the way up. And it was definitely getting above horizontal on the short drive (couple of kms and couple of biggish hills). Downhill it dropped pretty quickly down to a third then wanted to climb again.

It never used to get over 1/3 except once when I was really fanging it on Stocko in first for about 20 minutes which is why I am sure something's wrong. Radiator is an exact copy of the old one and is brand spankers so I'm sure it's not blocked (plus it drains with no hesitation).

[=SKB=]

Check the new thermostat actually works. Put in the freezer then drop it in a glass of boiling water and see if it opens.

[reprise]

When i first had my sierra, no matter what i did, the temp stayed around 1/3....even after 3-4 hours 4wd which included 1.5 hr drive each way up the freeway. no problem. It then started to overheat and blew gaskett. Had new head put in, and brand new radiator and hoses themostat etc etc same as yourself. The first time i drove it i noticed it creeped up to half way pretty quickly, something it had NEVER done before. anyways i was thinking something is wrong here. anyway left it be, went driving, went 4wd and it got hotter then it used to but never past 2/3 and thats after good 6-8 hrs continuous driving. That was about a year ago and its still fine. With all the new gear i assume it must just read the temperature better then it did prior. So may be nothing to worry about at all.

Now in traffic it gets about half way up, and it never did this before!

Hopefully you'll be fine.

[alien]

im having the opposite trouble of mine running cool! ie: at 1/8!! lol

[... rick]

What about an accurate gauge with actual temp readings? That way you KNOW where your at.

[Pyrotech]

im having the opposite trouble of mine running cool! ie: at 1/8!! lol

that makes 2 of us,

mine has never come anywhere close to half, thats even after a solid day of crawling (so bugger all airflow), hmm, any ideas?

[lay80n]

im having the opposite trouble of mine running cool! ie: at 1/8!! lol

that makes 2 of us,

mine has never come anywhere close to half, thats even after a solid day of crawling (so bugger all airflow), hmm, any ideas?

Check your thermostat. Check your auto choke. Get a acurate temp gauge too, the factory ones are only average.


Layto....

[Brendan-s]

What about an accurate gauge with actual temp readings? That way you KNOW where your at.

Top call, but from what I've heard it's mainly the send that goes, the actual guage usually is alright? (PS just send you an email)

Gonna go home at lunch and put it back in without the thermostat temporarily to see if that's what it is or not. Haven't actually seen the car running in daylight for about 3 weeks.

[Pinball]

flat on the gauge is where they are "supposed" to run...

mine runs icy, always has when it isn't blocked with crap.... causes massive issues with the auto-choke

if you think it's hot, check the shroud, check the fan. Bleeding the air as mentioned at the carby point... or run it for a few days and then check/top up...

Spock

[Brendan-s]

Well I reckon I found the problem. I picked up a too high temperature rating thermostat, rated to 95° so obviously bloody hot. Put it together without the thermostat and once it heated up (took a while obviously) I couldn't get it to overheat. Going to go and get a cooler thermostat tomorrow, what temperature guage setting should I be looking for?

Thanks for the input everyone. This weekend's trip will be the real tester so I'll see how she runs but I'm confidant it was all the result of a thermostat opening too late.

[zook4fun]

79- 85 is about what you are looking for. most are about 82 i think

[Brendan-s]

Got an 82, working perfect now. It heats up to running temperature when idling, then after 20 minutes of working it hard and letting it idle the gauge didn't budge.

Cheers for input