Sigma Overheating.... Ahhhh!

[mstrrab1992]

Ill have ur siggy if u dont want it, they must replace it under consumer laws! If they dont, sue them lol

[81GL]

I haven't read this thread in entirety since my last post, bit too much jibber jabber.

In normal operation I would not expect the bottom radiator hose & tank of radiator to be hot with in 15min. of operation with these older vehicles.
What you will probably find is the thermo stat is opening slightly, letting "some" coolant pass through until cool enough again. Being a cold start the coolant will be instantly cold so there is no need for it to cycle through the whole cooling system.

As Astronturbo77 suggested for an easy test, sit a thermometer in the radiator with the cap off & see what the actual temperature is. Or get an after market gauge that you can temporarily install, with the gauge just sitting in the engine bay. That way you will know what is going on.

On the other hand, if your doubting your self, maybe it wouldn't hurt for a mechanic to have a look at it. There is no substitute for experience.

[H8DAG8]

I haven't read this thread in entirety since my last post, bit too much jibber jabber.

In normal operation I would not expect the bottom radiator hose & tank of radiator to be hot with in 15min. of operation with these older vehicles.
What you will probably find is the thermo stat is opening slightly, letting "some" coolant pass through until cool enough again. Being a cold start the coolant will be instantly cold so there is no need for it to cycle through the whole cooling system.

As Astronturbo77 suggested for an easy test, sit a thermometer in the radiator with the cap off & see what the actual temperature is. Or get an after market gauge that you can temporarily install, with the gauge just sitting in the engine bay. That way you will know what is going on.

On the other hand, if your doubting your self, maybe it wouldn't hurt for a mechanic to have a look at it. There is no substitute for experience.

Hey mate, cheers for the reply.

The thing is, when the car actually overheated (got to just under H) I remember feeling the bottom hose and it was still not even warm, its was definitely cool. Surely the thermostat should have opened enough by then?

I might get one of those mechanical temp gauges then, are the ones where the unit/sender sits in the radiator hose (where you cut it) ok to use?

E.g. this http://www.trademe.co.nz/motors/car-par ... 704132.htm

paired with this http://www.trademe.co.nz/motors/car-par ... 934949.htm

The latter says it comes with temp sender, is that what's in the first link (as obviously it can't be where the factory one is because they can't be universal)?

[mstrrab1992]

cant hurt

[H8DAG8]

Oh one more Q, when I get the gauge and adapter and install it all, what temp is normal what temp is hot and what temp would be classed as overheating? For a 4g63 SOHC 8 valve carby RWD engine -- depends on engine I assume. All the Sigma manuals I have don't have the 4g63 engines in them because they're all Aussie books and only the NZ ones came with 4g63s

[mstrrab1992]

140 = over heating lol, normal id says around 80-85 degrees? thats just me but around that?

[81GL]

Something like this is what you are after: http://www.ebay.com.au/itm/Mechanical-O ... 27bf00fb15
-any retail store should have one if you want it straight away, just a generic $40 ~ $60 gauge will do the job fine.

No need to cut your top hose to fit it, remove the factory sensor on the manifold & stick that one in for a bit.

When your engine previously went, do you know what caused it? if it was the thermo stat, water pump, blockage etc, then yeah, bottom hose would stay cool-ish except for convection.

Not sure on exact numbers, I think Astronturbo77 mentioned something earlier? but if the thermo stat opens at 82, I guess under 95 would be acceptable.

[damian]

so with no thermostat water flows thru the motor and radiator, but doesn't get hot...

either it's too bloody cold in NZ. or you've got hold of a cold fusion motor

[mstrrab1992]

so with no thermostat water flows thru the motor and radiator, but doesn't get hot...

either it's too bloody cold in NZ. or you've got hold of a cold fusion motor

I concur, what he said

[H8DAG8]

Something like this is what you are after: http://www.ebay.com.au/itm/Mechanical-O ... 27bf00fb15
-any retail store should have one if you want it straight away, just a generic $40 ~ $60 gauge will do the job fine.
No need to cut your top hose to fit it, remove the factory sensor on the manifold & stick that one in for a bit.
When your engine previously went, do you know what caused it? if it was the thermo stat, water pump, blockage etc, then yeah, bottom hose would stay cool-ish except for convection.
Not sure on exact numbers, I think Astronturbo77 mentioned something earlier? but if the thermo stat opens at 82, I guess under 95 would be acceptable.

Ok yea I've had a look at the stores and I'm looking at around $100+ which I don't really want to spend at the moment on a gauge.
If this one: http://www.trademe.co.nz/a.aspx?id=411934949 comes with a temp sender will that be OK? I asked a question on that auction and he mentioned the temp sender being for under the dash?? Are there 2 types? Thought the temp sender had to be in the manifold.

When the head originally cracked? Was just age. Nothing actually failed the head must have just had too many cold starts I guess and the ali finally cracked a hairline crack where they normally fail.

Ok I'll when I get a gauge I'll post up what I get with the thermostat in. Just need to find the right gauge! Preferably on trademe.co.nz so it doesn't take long to get to me so if anyone has a spare minute and can look for one on trademe.co.nz and let me know that'd be much appreciated. As cheap as possible.

so with no thermostat water flows thru the motor and radiator, but doesn't get hot...

either it's too bloody cold in NZ. or you've got hold of a cold fusion motor

With no thermostat water flows great through both the motor and the radiator, the water does get hot, but the temp gauge stays just above COLD when I ran it for 20-30minutes. I guess with no thermostat that just wasn't long enough for it to get to running temp? Haha it's cold here but not THAT cold atm.

[H8DAG8]

Ill have ur siggy if u dont want it, they must replace it under consumer laws! If they dont, sue them lol

Lol sure I'll have some $$ if you don't want it ;) do they have to if I don't have the box? That what I thought.. as long as I had proof of purchase.

EDIT: Just realised the one I'm looking at on trademe is an electric one. Does the mechanical one run water into the actual gauge? Can't seem to find a cheap mechanical one. If, when I find one, the fitting doesn't thread into the hole in my manifold below the thermostat housing are there adapter threads that I can find to make it fit? Or do I specifically have to find a mechanical gauge that has the sender that fits

EDIT EDIT: Ah found one, http://www.supercheapauto.co.nz/online- ... escription

[81GL]

Depending on the ambient temperature, there is a good chance the engine will not reach normal running temp with the thermo stat removed.

That is a good sign, meaning the cooling system is doing its job well - cooling the motor.

Mechanical temperature gauges do not run the coolant into the cabin, they use a gas in there line to measure (measure pressure change i assume?). Mechanical oil pressure gauges on the other hand... they run pressurised oil up to the gauge. Not a good idea in the cabin.

Anyway... back on track, I think I have a spare one in the shed somewhere if you want it. Was given to me so happy to pass it on to someone who could use it, plus I'm curious my self to see the result. Not sure what postage is to NZ though ?? and how long it may take? But its yours for the postage cost if you want it.

Edit: The one in your last link will do the job fine

[H8DAG8]

Thanks for the offer mate very kind but I'm going to pop down to supercheap as 1 of the stores close to me has 1 left, and only $25 which is great -- is a mechanical one too.

Will install it today hopefully and post up what I find. Just to confirm, all the temps talked about on this thread (and the 82 degrees on the thermostat) are in celcius right? Pretty obvious they must be as 82'F would be far too low but best to confirm

[81GL]

Yeah, all in celcius.

Just on a side note, are you still running the standard carby?

[mstrrab1992]

Eep, probably not, but anywho

[H8DAG8]

Yes, standard carby. Everything is standard. Only 'mod' is 252 grind lumpy cam -- because I like the sound (if you don't like it get over it don't bother saying "why a lumpy cam and nothing else" ) and half of the exhaust re-done with a newer muffler like the standard one at the back as old one rusted out and this one gives slightly better performance as less restrictive.

Just got the temp gauge, will be installing soon.

[H8DAG8]

For f*******************k sake the mechanical temp gauge doesn't fit. The 'bulb' bit fits in the temp sender hole fine, the thread fits in fine to lock it in there, but it doesn't thread in far enough to make it a snug fit and seal it. It needs to be spaced out or have more thread on it. Realised also that if I installed this in the engine bay then I'd have no idea of the temp inside the cabin as the standard gauge and temp sender won't be in there/work.

So to have both, I'll need standard temp sender in there, and then the mechanical one installed somewhere.. in the radiator hose? The adapters I've seen have tiny holes, none would fit this mechanical temp sender in them, and this temp sender is so damn long it probably wouldn't fit that way either.

Stuck again..

[H8DAG8]

Found a little rubber o-ring to go between the temp bulb and the threaded bit to space it out, installed ok didn't leak (for now?).
Thermostat in. Ran car, not moving, was stationary, constant 1500rpm.

8 MINUTES: temp hit 82, then quite quickly dropped back down to 65-70ish. No radiator flow (or very VERY minimal to the extent it looked no different). Top hose and tank hot, bottom cold.

11 MINUTES: temp rose to 75ish and stayed there. Still no flow. Top hot bottom cold.

17 MINUTES: same as above.

20 MINUTES: no flow. Temp 75ish. Top hot, bottom warm-ish.

25 MINUTES: same as above.

HUH!?!?!? How can it hit the thermostat opening threshold then drop down and work its way back up to 75ish and stay there? For almost 30 minutes. The thermostat stayed closed as it didn't flow, just a slight swirl due to vibrations and shaking I think.

Is this normal?

EDIT: a car thermostat should be fully open about 20F above the temp rating on it, so about 10C, correct? And an engine should reach operating temperature between 5 and 15 minutes. How come mine reached the temp rating once, then dropped to about 10 under the rating and never nudged after 25-30min's of running the car at 1500rpm, stationary. May as well not have a darn radiator!

[mstrrab1992]

sell think bout what u just said, it should open 10degrees over wat its rated, so 82 - 92. its probably not getting that hold over there in freezing cold weather, id be trying to find a 75 degree thermostat and see if that fixes it.

[mstrrab1992]

but in all honesty, id be removing the thermostat for a week and see how it goes.. for some reason it seems like ur engine isnt getting hot enough, it may be the cold over in nz doing it?

[H8DAG8]

Wow guys calm it down. I'm the one with the car issues not you guys!
Lets keep it nice so I can get this issue resolved ASAP, you guys have been really helpful so far and I appreciate that - really wanting to sort this myself as don't want to fork out more $$$$ for this problem when I have a hunch it's a small problem that is just a mission to find.

The weather here isn't that cold! It has nothing to do with how the engine is running.
Thermostat's open at the temp rating they have, but they FULLY open ABOUT 10'C above that - is that not correct?

Just installed the mechanical water temp gauge in cabin and flagged the standard one. Thermostat is in. Everything is back on.
Going to take it for a good drive tomorrow and see what the temp does.
If after 30-45min of solid driving it doesn't get over 82'C surely there is something wrong? But what can make an engine run TOO cold!??!



astronturbo77: does what I said before (about the temps and flow etc. over time) sound right? Once a car hits the temp rated on the thermostat, should the thermostat continue to open until it is open fully, and then stay fully open as surely the car gets hotter and hotter until it reaches a constant(ish) temp above the thermostat rated temp? I can't understand why mine settled at below the thermostat rated temp..

[75wagon]

I HAVE DELETED SOME OF THE POSTS ON THIS TOPIC.

THIS CRAP WILL STOP NOW.

I'M OVER IT.

DAVE...

[astronturbo77]

it should open and stay around the thermostat opening temp... have you tried taking it for a drive with the new gauge yet?

[H8DAG8]

it should open and stay around the thermostat opening temp... have you tried taking it for a drive with the new gauge yet?

Hey mate.

Yea that's what I thought, but it definitely didn't stay around 82, was more like 75.
No didn't get time to take it for a good drive today with the new gauge, will do that tomorrow morning hopefully. Although in saying that, shouldn't being run stationary at 1500rpm for 30mins yield the same results? Or even hotter results?

Will post up temps tomorrow after the drive.

Once again thanks all for all the info. and help. Suprised no one has run into this (weird) problem before.

[81GL]

Going by the results of the mechanical gauge, wouldn't it suggest the cooling system is working as it should... ?

Keep in mind the thermostat is a mechanical device that does require some time to react, so when some coolant passes through at 80 degrees, it might not be fully closed until 75.

[H8DAG8]

Going by the results of the mechanical gauge, wouldn't it suggest the cooling system is working as it should... ?

Keep in mind the thermostat is a mechanical device that does require some time to react, so when some coolant passes through at 80 degrees, it might not be fully closed until 75.

I understand that by what the gauge is showing the cooling system IS working (so the old gauge must have been showing the car was overheating on the occassion when I pulled it off the road in error?) but should it be working THAT well? Surely after 30 minutes of stationary 1500rpm should have warmed the car to operating temperature which is surely above the thermostat rated temperature?? Or am I wrong?

EDIT: the thermostat never opened and water never flowed through the radiator after those 30 minutes, that's what has me confused.

[H8DAG8]

Ok, 35-40minutes of driving. Temp reached 82 within 5-10minutes, then dropped to around 70. Rose again to 75 and sat there for the remainder of the drive.
Got home, turned radiator cap to the pressure release point, and it did spit out some water and pressure and the water was extremely hot. Overflow water was stone cold.
After I'd taken the cap off looked at temp gauge and it was reading just over 82, say around 84-88 (damn gauge has stupid markings for 'C).

Can any mechanic on here tell me what this means? Is this normal?
I thought when the radiator water got that hot it dumped some into the overflow so shouldn't that have been luke warm or warm? Not stone cold?
And does this mean my cars operating temp is below the opening threshold temp of the thermostat? Isn't that odd!?

Cheers

[A112H]

Your thermostat has nothing to do with the overflow bottle nor does the temperature, as such. How the fluid gets into the overflow bottle is all about pressure. It should really be called a pressure relief bottle or something like that.
The thermo stat is controlled by the fluid temp, once it reaches its operating temp it will open allowing the fluid to pass from the head to the radiator. As the cooler fluid passes from the rad, through your engine it will make its way back to the thermostat and it will close again.
This allows the fluid in the rad time to cool down before being released into the system once again.
Your radiator cap operates on pressure; on the top it will have a rating. What this is designed to do is relive the cooling system of any pressure before causing damage. Your cooling system is a sealed system, if it starts to get hot and the fluid turns to a vapor (steam) it causes pressure. At this time the rad cap will release some of this pressure and fluid to the overflow to prevent the pressure causing any internal damage to gaskets or bursting hoses and things like that.
As a complete unit the cooling system is a fine balance, managing heat and pressure, if either is incorrect i.e.; wrong pressure cap, thermostat too hot or cold, no coolant, water pump failure or a blockage it will through this balance off and the system will become inefficient.
Having said all that, what you describe above sounds fine to me.
The problem with a numerical gauge (and the reason they are not fitted by the factory) is that you will pay too much attention to it.
The temperature should rise initially, this is how the engine warms to a good/safe operating range, and the first opening of the thermostat will always be the biggest jump as the fluid in the radiator is at its coolest having not been through the cycle yet so a drop to 70 is fine. Sitting at 75 for about 30 mins driving sounds spot on to me, if it isn't fluctuating after a 10 min run getting up to temp then I wouldn't be at all concerned.

Well that is my rant for the day, it is only 7:30 and I have already hurt my brain

[H8DAG8]

Haha cheers mate - yep that's completely how I understood the cooling system to work.
But hitting the 82'C mark only once in a 30-40minute drive just sounded .. odd to me.
I guess my car just runs cooler than I'm used to in other cars. Good thing I guess.

If you don't mind me asking, are you (or were you) a mechanic by trade? If so, what would you say would be an "overheating" temperature for my engine? (4g63 SOHC Carby 8 Valve RWD, 2L.)

Cheers

[A112H]

No I am not qualified but have always worked around mechanics and my old man onwed a wrecking yard/workshop
Anyway, most engines are safe up to about boiling point, but it really depends on condition and age of the alloy, gaskets, hoses, water pump and radiator as to how much pressure and temp they can handle.
As I mentioned before it is the pressure boiling water puts on the system that will cause damage as much as the heat.
This is a basic breakdown of boiling points;

Pure Water - 100 C

50/50 mix of Coolant/Water - 106 C

70/30 mix of Coolant/Water - 113 C