[whincup]

well ive seen a few overheating issues on the forum... a few similar, but not quite the same... so it only does it at highway speeds (>80km) in 5th gear. drop it to 4th and (despite heavy revving) it actually runs cooler. doing 100km/h the temp gauge hits the red, and i have to drop to 4th and take it easy for a minute or two... i can sit on 60 or 70 no worries in 5th gear through town. it still runs warmer than it should, above halfway but still below 3/4.

i changed the thermostat, although it was a cheap brand one and the seal was a little small, but im about 99% sure thats not the problem. i want to know opinions on this theory:
from what i understand, the engine recycles a little bit of used exhaust gas back into the air intake, to make it run a little leaner, and this helps to cool?? i dont understand it properly, i may have just read that wrong... but at least one of the bolts for my extractors has come off, and theres black soot marks on the engine block where its blowing out exhaust from the gap there. could this mess with the system that recycles air?? its going in on wednesday for new extractors anyway, just hoping it kills 2 birds with one stone...

only other thing is the hose that runs from over the extractors to the air intake broke off a few months back, but from what i understand (again, could be wrong) this only helps warm the engine up in cold weather...

if not, i guess a new radiator is next on the shopping list...

[Ben_Sierra]

Put it this way... An improperly sealing exhaust manifold is not a good thing... If you are blowing sooty exhaust all over the block, even if it isn't causing your cooling problems, its hardly something you should knowingly leave unfixed... Its not like bolts are expensive or hard to fit...

[Fmoss3]

i must be the only person in australia that has a problem with his sierra running too cold.

seriously if its a cold night and i put the heater on its only just above the bottom mark of the gauge.

[Ben_Sierra]

Nope, mine runs pretty cold too...

[MacDaddy]

whincup wrote:

well ive seen a few overheating issues on the forum... a few similar, but not quite the same... so it only does it at highway speeds (>80km) in 5th gear. drop it to 4th and (despite heavy revving) it actually runs cooler. doing 100km/h the temp gauge hits the red, and i have to drop to 4th and take it easy for a minute or two... i can sit on 60 or 70 no worries in 5th gear through town. it still runs warmer than it should, above halfway but still below 3/4.

i changed the thermostat, although it was a cheap brand one and the seal was a little small, but im about 99% sure thats not the problem. i want to know opinions on this theory:
from what i understand, the engine recycles a little bit of used exhaust gas back into the air intake, to make it run a little leaner, and this helps to cool?? i dont understand it properly, i may have just read that wrong... but at least one of the bolts for my extractors has come off, and theres black soot marks on the engine block where its blowing out exhaust from the gap there. could this mess with the system that recycles air?? its going in on wednesday for new extractors anyway, just hoping it kills 2 birds with one stone...

only other thing is the hose that runs from over the extractors to the air intake broke off a few months back, but from what i understand (again, could be wrong) this only helps warm the engine up in cold weather...

if not, i guess a new radiator is next on the shopping list...

I would take a guess and say maybe your water pump is not pumping to well, and not moving the coolant enough until you keep the revs up... it could also be a clogged up radiator, but i dont think so... and one other thing, if your cooling system isnt pressurized properly, the coolant will get very hot alot quicker than normal...
A leaking exhaust manifold will not help your engine run well.. but that would effect engine performance and tuning... as far as i understand, it recycles exhaust gases because of the enforced and stupid emissions control system... not sure how it would cool the engine, it just makes it run dirtier and under perform, recycling burnt exhaust gases.....

Anyway, thats my thoughts/opinions, hope it helps...

[morpheus]

i had a sierra and vitara both with overheating issues. My vitara got hot enough to crack the head. Turns out all it was, was a blocked radiator. I took it out myself, they cleaned it out, put it back in and now it never gets above a quater, and it only cost me $80, probably worth a try. And even if that aint the problem, @ least you have eliminated one possibility, & will know you have a clean radiator.

[steak_knife]

morpheus wrote:

i had a sierra and vitara both with overheating issues. My vitara got hot enough to crack the head. Turns out all it was, was a blocked radiator. I took it out myself, they cleaned it out, put it back in and now it never gets above a quater, and it only cost me $80, probably worth a try. And even if that aint the problem, @ least you have eliminated one possibility, & will know you have a clean radiator.

X2 on blocked rad.

[royce]

I would say you tune is off and you are pushing it at the lower revs and making it heat up, back to 4th or going slower is taking some load off, which some times is All it takes

the EGR takes exhaust gas in some circumstances and injects it into the intake, this reburning of gas lower Nox or some other gas emissions, and from memory is locked out by the 4th and 5th gear switches on the box anyway, plus with extractors you nee a little pipe that goes from the number 4 cylinder pipe back into the head via the header flange about 2cm behind it, most dont have this so the egr is blanked off anyway

[31zook]

sorry for the hi-jack, but should a sierra at running temp have the needle sitting parallel with the bottom of the gauge? Not on the bottom but up a bit above the lower marking....

holy crap i did bad at explaining that....

[royce]

I reckon from old age and million other factors they will all read differerent, some even read different depending if the lights are on

the best thing to do with your car is when its up to temp stick a thermometer in the rad and check the temp is around the 82-92 mark and remember where that is on the gauge, then go for a long drive and come back and turn the engine off and leave the ignition on and see how high it gets, that point is probably as high as you would ever want to see it while driving

[hutch]

x3 dodgy radiator, also agree on the dodgy water pump issue.

[whincup]

hmmm... ok well i have most of next week off, guess i'll give flushing the radiator a go, see what happens. there are a few bent fins on it, but not many and i dont think thats the problem. i didnt originally think that blocked rad would be the reason as i would have thought it would have run hot at low temps instead of high...
how much effort is water pump to replace?

[hutch]

[quote="whincup"]i would have thought it would have run hot at low temps instead of high...
quote]

Huh?

[steak_knife]

hutch wrote:

whincup wrote:

i would have thought it would have run hot at low temps instead of high...
quote]

Huh?

Beat me to it..

[whincup]

speeds sorry. thought it would run hot at low speeds instead of high speeds...

[jdk81]

whincup wrote:

speeds sorry. thought it would run hot at low speeds instead of high speeds...

My experiences

Due to sleek zook aerodynamics my high speed fuel consumption is stupidly high

At 80 km/h I get 7-8L/100 km and 100 km/h its closer to 12 L/100 km

As I am going through fuel at a faster rate (50% faster) there is a lot more heat in the engine, which needs to be transferred


At 12L/100 km (100 k/hr)
44 MJ/kg
.8 kg/L

fuel energy input is 117kW
47 kW is leaving the crank into gears etc and eventually to wheels to fight the drag.
leaving 70 kW of excess. Lots will go out the pipe, there will be pumping losses etc, but the radiator is working pretty damn hard and it probably wasnt designed to function at this level after 20 years of use and abuse.