Temp Gauge - How Hot is Ok?

[CaesarBob]

Not sure if i'm just overly paranoid or not.

To set the scene, on the M20 I've recently replaced the thermostat for BMW 80o one, changed the coolant and water pump. Viscous fan was given a good degrease, passed the rolled up newspaper test and there are no signs of leaks. Appears to be fully bled with no air coming out the bleed nipple, the heaters get hot in good time and the brass nut is nice and tight. Under normal running the needle sits just below half way and drops slightly further when cruising downhill on no throttle.

So the question is when sat in traffic or idling, as soon as the temp needle creeps passed half way I get paranoid and whack the heater on full to cool proceedings down. How far can i safely let the needle rise before taking evasive action? The owners manual says anywhere between red & blue zones is fine, but my old iS never really when went over half way in 5yrs.

What do you reckon?

[Banjo1981]

A slight bit of creep is to be expected in traffic and as I understand it there is very little difference temp wise between the middle section of the gauge. probably just paranoia as you said.

[mattrs]

I have had a few of these now and they typicaly sit just under half, they will creep up under certain conditions...... I personaly wouldn't worry unless it went over 3/4, especialy given the maintenance you have done.


Prehaps try not putting the heater on and seeing what happens

[CaesarBob]

Prehaps try not putting the heater on and seeing what happens

Looks like i need to take a couple of brave pills and tough it out! Just needed some moral support before i play the cracked cylinder head lottery.

[mattrs]

Look on the bright side, its probably not that and if it is its an excuse for a hot cam! (no pun intended).

[aeberbach]

Where exactly does it stabilise? Does it continue to creep higher if you don't put the heater on? If it reliably stays well under the red, no problem. Mine sits at just under half way BUT this depends heavily on the tolerances in manufacturing present in both the temp sensor and the gauge. Mine could well be hotter than yours.

[mrLEE30]

the middle portion of the guage only covers a few degrees of temp i.e. in side the three white lines.

when you stop in traffic the air flow is obviously less so the engine begins to heat up, the viscous fan then does its job by becoming hot and locking up the clutch to make the fan spin faster, thus pulliong more air and stabilising the temp. this takes some time. if the temp is inside the white lines it is OK. only when you approach the red shoudl you worry and turn on the heater.

for info both my cars do this here, and i live in 50C heat!

mrlee

[CaesarBob]

Thanks for the info.

I haven't driven the car that far yet and for the short time spent in traffic I haven't let the temp rise too far. I think i'll let it get a bit warmer and see where it settles.

Cheers

[ivqii]

I don't think that there is an E30 owner anywhere who isn't at least a bit paranoid about engine temp

I know that I am

[ron2n]

I have same problem, when I drive even on a highway (where air cools down the engine) needle goes above 90C, If I don't turn on the heater temperature will stop on 110C (third bar) If I turn on heater temp comes back to 90C. should I worry about this or relax until needle is about 110C?

[eta]

I think you have a obstructed radiator ron. You should not need to turn the heaters on to keep the engine cool.

[mrLEE30]

I have same problem, when I drive even on a highway (where air cools down the engine) needle goes above 90C, If I don't turn on the heater temperature will stop on 110C (third bar) If I turn on heater temp comes back to 90C. should I worry about this or relax until needle is about 110C?

how do you know whaty the temp is? there are no marks to indicate temp.

if the thing gets anywhere near the upper line of the three middle lines then you have either the wrong thermostat or as suggested a cooling issue i.e. blocked rad/worn water pump/ leak / wrong cap

[dazleeds]

in my experience anything past dead centre on the gauge is to be worried about

most run between the qtr and halfway mark

did you rebleed after driving the car a few miles? i've had a few been a sod to bleed and needed doing 2 or 3 times before everything was spot on

[CaesarBob]

That's kinda what i've found previously Daz.

I've bleed it after each trip i've made since changing the coolant. Maybe there's still a bit of air lurking somewhere.

I should be bleeding while the engine is still warm rather than stone cold, yes?

[daimlerman]

Bleed with the system pressurised.
I would suspect a partly blocked radiator,Mr Moore does suggest that these are a 100,000 mile sevice item!The buggers will pass a 'hosepipe' test but the tiny tubes within can still be partly blocked with a build up of crud.

[CaesarBob]

I forgot to include it's had a new rad too, in the initial post.

I'll keep checking for air for a little longer and make sure the needle never passes 3/4.

Cheers

[clipper]

Be brave.

My E30 325i came back to me after being stolen with an engine full of mayo. H/G was gone and I suspected the worst but the head was OK.

Then last month the top hose burst on the motorway and it lost all it's coolant. As I had the wife and miniclipper with me I cruized to the next services (about 2 miles) and fully expected the head to be scrap. But no, I've replaced the hose and the rad (which was causing slight overheating on the motorway like Ron's is doing) and all is good. No H/G or head problems.

Maybe I'm just lucky, but I reckon you've got to have a serious localized overheat to crack the head.

DISCLAIMER: It obviously does happen so don't blame me if it goes wrong !

[Morat]

My personal rule based on nothing more than paranoia is to shut it down if the temp goes above 3/4 (the white line before the red starts). I've never seen the temp above that line on a fit and healthy E30.

[CaesarBob]

That's the philosophy i am adopting and i'll continue to check for more air in there.

[325zimmer]

After a H/G change on 325, it never used to get to the middle on the guage, so I ran a earth from the base of the sender to the earthing point on the strut, and bingo sits in the middle nicely. Now there is very little wavering in traffic.
Its worth a try.

[CaesarBob]

I don't get it. What does that do?

Shouldn't the sender already be earthed somewhere or is it that fact the earth strap is knackered?

[325zimmer]

Basically yes, the sender earths through the engine, to the strap and body. But it a has a way to go thro the aluminium stat, head then block to the strap. I even changed my earthstrap as well with no joy. So i tried earthing it direct, and it helped.

[KimH]

Once it's warm, my 325 sits exactly on the first white line all the time. It used to creep up in traffic a little so I replaced the viscous fan. Now it's back to the quarter mark and stays there - even in traffic.

[markus_74]

so, the normal temperature is below and to the centre gauge, no more even it sligthly?

[agd931]

As MrLee, apart from I live in 40C heat!

[mrLEE30]

As MrLee, apart from I live in 40C heat!

when it drops down to 40 we wear a sweater!

to reply to all.....the E30 gauge is non linear so the middle portion of the guage only covers a few degrees. most E30's should sit just below half when in motion but dont worry if it creeps up to the half way and even the "hot" white line, this is normal in a situation such as a fast hard drive and then pulling to a stop, the engine is hot and thus the slower speed will mean less water circulating and the engine should warm up a bit, this you see on the guage.

when you worry is when it gets toward the hot side and does not come down, or runs in the hot side all the time, if this is the case then first bleed the air, then inspect or change the thermostat. if this does not help then inspect the radiatior, then look to water pump, and finally head gasket after a pressure test.

loosing water is a big issue caused by leaks or head gasket. but most E30's will run with the water toward the bottom of the expansion tank so dont confuse leaking with the system finding its own level, i.e is there is alsways water in the bottle its probably OK.

and as for your chilly 40C this is what we had a few weeks ago, E30 running faithfully as ever.....

[KimH]

so, the normal temperature is below and to the centre gauge, no more even it sligthly?

I guess cars destined for tropical markets have bigger rads/ fans/ or both. Here in UK, where anything hotter than 20 C is a heatwave, it would seem the norm for a 6 pot is between 1/4 and mid point.

[Alex]

As MrLee, apart from I live in 40C heat!

when it drops down to 40 we wear a sweater!

to reply to all.....the E30 gauge is non linear so the middle portion of the guage only covers a few degrees. most E30's should sit just below half when in motion but dont worry if it creeps up to the half way and even the "hot" white line, this is normal in a situation such as a fast hard drive and then pulling to a stop, the engine is hot and thus the slower speed will mean less water circulating and the engine should warm up a bit, this you see on the guage.

when you worry is when it gets toward the hot side and does not come down, or runs in the hot side all the time, if this is the case then first bleed the air, then inspect or change the thermostat. if this does not help then inspect the radiatior, then look to water pump, and finally head gasket after a pressure test.

loosing water is a big issue caused by leaks or head gasket. but most E30's will run with the water toward the bottom of the expansion tank so dont confuse leaking with the system finding its own level, i.e is there is alsways water in the bottle its probably OK.

and as for your chilly 40C this is what we had a few weeks ago, E30 running faithfully as ever.....

How Hot Feck me.

[hongkongfuey]

i had a problem like this and changed the brown temp sensor on the thermostat, it never went above middle in traffic

[markus_74]

As MrLee, apart from I live in 40C heat!

when it drops down to 40 we wear a sweater!

to reply to all.....the E30 gauge is non linear so the middle portion of the guage only covers a few degrees. most E30's should sit just below half when in motion but dont worry if it creeps up to the half way and even the "hot" white line, this is normal in a situation such as a fast hard drive and then pulling to a stop, the engine is hot and thus the slower speed will mean less water circulating and the engine should warm up a bit, this you see on the guage.

when you worry is when it gets toward the hot side and does not come down, or runs in the hot side all the time, if this is the case then first bleed the air, then inspect or change the thermostat. if this does not help then inspect the radiatior, then look to water pump, and finally head gasket after a pressure test.

loosing water is a big issue caused by leaks or head gasket. but most E30's will run with the water toward the bottom of the expansion tank so dont confuse leaking with the system finding its own level, i.e is there is alsways water in the bottle its probably OK.

and as for your chilly 40C this is what we had a few weeks ago, E30 running faithfully as ever.....

How Hot Feck me.

what mirror at the picture? it is good has a direction and temperature sign

[mrLEE30]

GMC they all have temp and direction in mirror. and yes Middle east spec have longer and slightly thicker rads