overheating - thermostat or radiator? *cage thread*

[lukamon]

hey, took the car into the garage today to have the thermostat replaced, as it's been not heating up at all for a while. the garage is about 200m from my house. took it for a drive this evening and after about 5 miles it started to over heat

was able too keep it at a reasonable temp by having the heater on full blast, and when i had a look later, there is _no_ pressure in the expansion bottle and the water in there is cold. also, the water going in th top of the radiator is hot but the hose to the pump the other side is stone cold

oh, the thermostat + gaskets were supplied by me, as i was going to do it myself but didnt have time, so it had been sitting around for a while.

any help appreciated, cheers.
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killa wrote: Im an ass man myself

[rotax81]

my first thought is a blocked radiator.
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[Robby]

Seeing as the stat is the thing that was changed, that is the most likely problem. Only place it can dump any heat is through the heater.

[lukamon]

well, im inclined to say it isnt the stat, because the engine heats up just fine now like it used to, stays at perfect temp for 5 miles or so, and only then overheats. surely if it was the stat stuck shut it would just go strait into the red?
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killa wrote: Im an ass man myself

[MattEMulsion]

What car is it?
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[Ben.]

blocked hose? flush the system out as best as you can, try and make sure no hoses are blocked, if it still does it you know its probably the stat.
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[Stelmer]

I'd remove the thermostat, put heater on hot and remove the bottom hose to the radiator.

Flush with a hose through where the thermostat goes and you'll be surprised by how much crud comes out through the bottom rad hose.

Do the same through the radiator. If it's bad, remove it and flush backwards. If you cannot flush the rad, it will probably need replacing.

Is there any evidence of previous coolant leaks or damage on the rad fins? Could've been blocked by that stuff you stick in to block leaks. I'd definatly remove the bottom hose and check inside it and look into the rad too.

I've also heard of people putting eggs in the coolant to stop leaks.

[Robby]

Sounds like the stat is stuck closed.
The stat doesn't open up until the coolant around the engine is up to around 75 celcius - so registering about 1/3 or more up the temp gauge. On most (all?) cooling systems the water can still get to the heater before the stat opens, to get the cabin warm as quickly as possible.

The warm up speed depends on the thermal efficiency and coolant capacity of the engine. Modern diesels and small petrols will be slower than old high performance petrols.

[NiteMare]

first of all we need to know what car/engine it is ...

an awful lot of cars cooling systems have to be bled to get airlocks out of them ....


i suspect this is your problem rather than blocked radiators etc'


and i suspect you mean there is no water in the expansion bottle (might be wrong)
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it ain't broke...

i ain't fixed it enough

[lukamon]

chhers guys, its a fiesta zectec - s (1.6) 2000 x reg, phase one engine.

updates - took the bottom hose off the radand flushed through the rest of the system, the rad is fine, water pissed out the bottom fast as i put it in the bottle. now having refilled the system i get pressure in the system and hot water instead of coldin the bottle, but still it overheats and the pipe from the bottom of the rad is only lukewarm. maybe the stat isnt opening properly?

btw - on the owners forum i hear a lot about the heater control valve on these car but mine is fine so it isnt that. (tested)
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killa wrote: Im an ass man myself

[Finglonga]

[Rockhopper]

Stats almost never fail shut, they are designed not to do that. If the rad is running okay my guess would be an airlock somwhere.

[stevo as b4]

I agree that the stat is the most likely culprit, and it's fairly easy on some cars to get to and remove for testing and replacement. If the Rad is fine, and the hoses are all in good condition, then i have to say id be thinking about the water pump next.

Having said that, most car's that overheat with a failed water pump, usually do it at high speed like barrelling down the motorway at high cruise speeds, when the cooling system has to work harder to get rid of the heat from the engine.

I have some sort of cooling system problem on my Astra, in that the temp needle never seems to move off the cold mark, and yet there is plenty of coolant in the system, and the cabin does still get warm eventually. It's too cold to look at it now before the spring, so i'll wait till then to service the cooling system and change the stat.

[Ichy]

[stevo as b4]

Cheers! I was going to change the stat anyway, as i can get it out without taking the cam belt off thankfully. I need to change the cam cover gasket and possibly the cam carrier to head gasket, as i have a bit of a dribble of oil coming from this area, and making a mess on the drive. I was going to reverse flush the rad and coolant pipes, and then flush and re-fill the system with some decent antifreeze mixture.

Rover 100's are a bit of a pain to work on, but at least the single cam K-series is a bit less prone to HGF than the 1600 and 1800cc 16v versions.

[NiteMare]

ok this thread has got a little confusing so i'll try and clear a few points up ....

most cars that start overheating (modern cars) have the problem caused by the owners not routinely checking the coolant levels are correct until they get the guage telling them it has over heated...

then all they do is top the expansion tank up without clearing any airlocks or allowing the coolant levels to settle before walking away thinking they've finished the job...

some (quite a few not all) cars have TWO points on the cooling to bleed air from, make sure you find them all...

some have NO points to bleed from as they are a self bleed system...

some are real fuckers to bleed (bmw's), some are easy (rovers, but the steel pipe bleed point regularly has corrosion sealing it so you need to poke a strong needle thru to clear the crap)...

only car i've known to commonly have the waterpump fail on is BMW (plastic impeller which loses it's blades) unless you're talking about the seals and bearing....

i think in 30 plus years of working on cars i've only ever once or twice HAD to change thermostats, thier failure rate is really low but as said before they would usually fail SHUT...

if your coolant has been drained to replace pipes, radiators or anything else then always open the heater valve (but turn off the cabin fan) once refilled and bring the engine up to full working temperature so that the radiator fan kicks in whilst keeping an eye on the gauge and checking for leaks/overflows

p.s.
always screw the expansion tank cap on tight, water boils at a lower temperature if it is not kept under pressure....

now grab the manual for your car and follow the directions in it rather than a bunch of guesses on an internet forum or the next thing you'll be doing is skimming the head along with having the valve seats sorted (zetec engines bugger the seats when they overheat)
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it ain't broke...

i ain't fixed it enough

[lydanial]

onm my brothers old fiesta he had a similar problem after trying everything we could think of we actually took the resevoir return pipe off and left it off till the water became boiling coming through.

this seemed to expel air and was right after that.

dumb luck? maybe. worth a try? definately.

sorry i missed your last update somehow.

have you tested the temp sender unit?? if you have and ive missed that too then bugger.. bad headache and trying my best.

[lukamon]

sigh, the bloke at the garage now thinks it uiasnt the stat it might be a head gasket i doubt it. maybe the system was getting up to temp and took a while to overheat because a teeny bit of water was pissing through the hole in the stat? (there is one drilled in the flange)
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killa wrote: Im an ass man myself

[Ichy]

Take the thermostat out and see what happens.
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[NiteMare]

[lukamon]

when has any car ever had a waterpump driven by the cambelt?

anyway, its been taken out of the hands of the spannermonkey. headgasket my arse. when i say overheting,i meant it was running at 106 - 115 deg instead of 90.

oh well, have to do it myself i suppose. the stat is beind the alternator meaning you have to take out that and the aux. belt to get to it. sigh.

no water loss and no bubbles coming through the header tank. will change the oil at weekend to check for white crap aswell.

the courtesy car (a fiat difficulttospell) is rather fun though
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killa wrote: Im an ass man myself

[NiteMare]

[Finglonga]

[Robby]

As has been said a few times, before people hopped in with tales of woe over a head gasket, whip out the stat and heat it up in a pan of water with a thermometer. You want to see it starting to open around 70 celcius, and full open by around 85.

Before you car went in it wasn't heating up. The only thing the garage changed was the stat. Therefore, the most likely problem is the stat.

One other thought - the garage should be fixing this. Whatever they did to it is what's making it overheat.

[lukamon]