cant keep stable temp

[adrianphu123 73]

Hey guys, recently i've been getting temp fluctuations of 1-3 bars, sometimes rapid changes sometimes gradual. The motor has a low temp thermostat so ideally in this weather it should run at 1-2 bars. Temps will generally drop once you get moving. 

 

Im thinking the thermostats starting to go bad. What do you guys rekon?

[gerg 10,871]

There are lots of scenarios that can cause this problem:

 

Blocked radiator core

Water pump impeller corroded

Cavitation in water pump (higher rpm)

A/c operation

Stop/start driving

Visco fan operation

Ignition timing/advance

 

All these need to be checked. That said, if the temp never goes over half, I wouldn't worry about it.

[adrianphu123 73]

Radiator was flushed out and i run a top hose filter
Water pump replaced 3 months ago
No A/C

Temp still fluctuate on the highway or at the lights
TIming hasnt changed

So I'll be replacing the thermostat, its not expensive.

Would you guys go for a 71 degree or 82 degree thermostat?

[adrianphu123 73]

plus has anyone used a stant thermostat? they dont have a jiggle pin, but seem to have a very small nick on the inner plate. Is this the air bleed?

[revhead 1,392]

id go the hotter thermostat in the colder months ,the jiggle pin is a by pass ,check that fitler isnt slowing the water flow,i myself never bother with the top hose filter,

also check under acceleration,that the top or bottom hoses are not being sucked closed ,flat ,this could cause your probs 

[adrianphu123 73]

I ended up putting in a 160F(71dgree) thermostat because the one i pulled out appeared to be a 160F one. Had 300/400/160 marked on one side and V161 on the backside on the part that moves. The one i pulled off didnt have a jiggle pin either but did have a notch so visually new and old are identical. I placed the notch at the highest possible orientation.

 

The temp fluctuation didnt start after i installed the filter so i can discount that. And whether you're accelerating or not has no effect, its all over the place. 

 

Tested the old thermostat in boiling water and it does open but i didnt test if openings were consistent with the rated temp or not.

[dizzy616 183]

yeh i can vouch for those filters i reckon they are a good thing. sometimes they catch some shit that you do not want running through the engine. i use to use one. my dad uses them on all his cars. they dont seem to upset flow unless their blocked up. and that means that something might be wrong. or your not cleaning it enough. 

ive allways meant to run them in all my cars. but i got slack.

problems i can think of.
might have a block somewhere in the radiator. sometimes flushing wont fix this
might have a temp sender thats on its way out? or problem with the wire running to the temp sender
might have a problem with the water pump
fan operation
 

feel the radiator hose when its warm. then feel it when its fluctuating and compare if theirs any difference. you can even stick one of those roast thermometers on the hose hold it there for a bit and get a stable reading. instead of going by touch

[bear351c 10,270]

Any updates ??

 

Sounds like a sticky thermostat....

[n00bus m@x1mus 465]

Have you proved its not a fault with the cluster first?

[revhead 1,392]

you need to visually check you hoses ,if you driving the water pump can and will pull soft radiator hoses flat as a tack and stop your water flow ,as a mechanic ive seen this quiet a few times ,so when your idling it wont do it.,i mean you lift your foot off the accelerator, the hose opens, then the water flows again ,allowing the motor to cool a bit,just a thought

[adrianphu123 73]

turns out in my haste, i cut the fanbelt and the spares i had are too long(1040 fits and 1060 is too long) better i find out here than the side of the road i guess.

 

No updates until at least tomorrow. I have heard of that happening but dont think its the hoses as both were replaced about 3 months ago.

 

How do i test the cluster? I had the sender tested (somehow?) a few years back but its been consistent ever since.

[n00bus m@x1mus 465]

Get youself a cheap ir temp gun from supercheap will help u find your problem or a simple mech temp guage.

[adrianphu123 73]

just an update, overall im happy with there its at

 

first drive, temps rose to 3 occasionally, all the air still hadnt bled out of the system

 

let it cool, topped it up and went for a second long drive. Temps stayed at 2 bars. 

 

Will continue to monitor over the next few days.

[bear351c 10,270]

So, you changed out the 'stat ??

[adrianphu123 73]

yeah just changed the thermostat and belt. no other changes. went for another drive today. everything seems fine.

[bear351c 10,270]

Awesome news.  Good stuff.

[adrianphu123 73]

turns out its still doing it, intermittent though.

 

Not a headgasket since temp goes up and down, top hose pressure is ok, no water and oil mixing.

 

Will try the fan clutch, i did notice that was leaking when i did the water pump.

[LTD083 278]

Mines doing the same so interested to see how you go. I changed the stat because it was reading too cold, which made it worse. It has improved with a few runs but still moves about a little. Ive narrowed it down to some sort of electrical issue as in unstable voltage. Havent done anything further with it now ive ruled out a mechanical issue.

[adrianphu123 73]

just changed the temp sender and the fan clutch. Still doing it.

 

It'll run at 1-2 bars for a period of time and then have an episode of fluctuation. 

[revhead 1,392]

if the rise and fall of the temp gauge,are minimal it could be the thermostat opening/closing etc

 

you could have a blown head gasket,it could be gone between cylinders or blowing compression,into the water galleries,this will cause silly temp problems  

 

not milky oil

[adrianphu123 73]

top hose pressure is normal and its not missing or running rough

[Vannin 2]

I would expect to see minimal temp fluctuations in a correctly working cooling system!!!!!!!!

[revhead 1,392]

top hose pressure is normal and its not missing or running rough

get yourself a leak down tester ,and pump the system up to see if it hold pressure,if it does its all good ,but if it slowly leaks down you will be able to find the leak if its external

[adrianphu123 73]

I'll look into that. I put on an old radiator cap that i know is good, appears to have fixed the problem somewhat. Will monitor over the next few days