General is it a sticky thermostat?

[stillzy]

Hi, i have a fiat bravo and noticed the temp would be one marker below the half way point on the dial and then every know and then would go down to the next marker (roughly) and then work its way back up?

my thoughts were that the thermostat is sticky and opens realy quickly when its gets to the running temp and all that cool coolant in the rad comes gushing in and makes the coolant temp go down more than it should.

i have used a coolant flush, drained it and it was FILTHY so i done it again, then again untill the water was clear ish.. and it seems to be better, doesnt do it as much and not realy at all on motor way which was when i noticed it more.

im going to replace the thermostat tomorrow.

first thought it was the head gasket but plugs, oil seem fine and doesnt apear to be loosing coolant?

if any one can throw some advise my way or let me know if they have had similer problems and if you sorted it...

thanks for taking the time to read.

 

[bluejohn125]

You've done the right thing flushing the system, if it's been really neglected and filthy this can mess up the thermostat so you're right to change that. You may find that there is still residual crap settled at the bottom of the rad.

Make sure you bleed the system properly (rad bleed screw, then hose into cabin / heater, then hose out of heater). Obviously heater set to full when you're filling.

Fluctuating temperature usually means low coolant, not the stat / rad suddenly opening.

 

[stillzy]

You've done the right thing flushing the system, if it's been really neglected and filthy this can mess up the thermostat so you're right to change that. You may find that there is still residual crap settled at the bottom of the rad.

Make sure you bleed the system properly (rad bleed screw, then hose into cabin / heater, then hose out of heater). Obviously heater set to full when you're filling.

Fluctuating temperature usually means low coolant, not the stat / rad suddenly opening.

cheers for the reply BJ (giggle), what could i do about the crap in the bottom of the rad then, other than replacing as it doesnt look that old. I did bleed the system but with only the rad screw and 1 screw on a pipe at the back of the engine, so theres 2 back there to bleed is there?

thanks again, off to go change that thermostat

 

[wrightyHGT]

Undo bottom hose and run hose pipe through.....replaced my thermostat couple weeks ago, easily bled through it was just pain that thermostat a sealed unit and not especially cheap.

Only the 2 bleed points as you say. Rad and heater hose.

 

[bluejohn125]

Bleeding process depends on the car engine etc, mine is a 1.2 16V with little bleed screws on the in and out hoses going through the bulhkead (one is on a side-extension to the hose).

I wasn't able to do a hose flush so I just refitted the bottom hose, poured a kettle of hot water into the rad, let it stew for a while, then whip off the bottom hose and let the mucky residue gush out. Repeat as necesary. No need to fill system properly, run to temperature, drain the whole thing etc etc.

Mine was full of rusty brown/orange gunk due to a heater matrix leak. Thermostat was crappy too.

 

[stillzy]

cheers wrighty.

ok guys replaced the stat, bit more of a job than i thought, i removed battery and battery tray and the ecu to get good access to it, cost me £60 which i wasnt expecting but hay its done.

it still does it though!

but now its one thing i know is good, and i can claim back on it at the end of the year on my tax return so.....

fella in the shop also said it could be part of the rad blocked with crap, said to check to make sure its all hot,(it was), and said could also be the water pump...

im going to do the cam belt any way so not to fussed gonna check online for the water pump, will do the belt withen the next few days probably, fingers crossed.

ill post back if i get it sorted but in the mean time if any one has any thing else to add.....

thanks

 

[bluejohn125]

Well it sounds like you're on the right track.. you can be confident in what you've done. I'm assuming you put nice new antifreeze in it and you are using the car, that should help to shift any extra redidues that may be hanging around.

When you do your water pump (may be a red herring, i'd expect it to fail by leaking or having a rough / seizing bearing) you can drain the coolant again and see how it looks.. any extra crud that comes out should settle in your drain bucket/ bowl and the coolant should be reusable. If there is crud then keep flushing before refilling, and maybe add another shot of coolant flush while doing it just to be sure.

Of course you could be observing a genuine effect of the rad / stat opening, but I'd say it's normally not noticeable unless you were really looking....

 

[stillzy]

Well it sounds like you're on the right track.. you can be confident in what you've done. I'm assuming you put nice new antifreeze in it and you are using the car, that should help to shift any extra redidues that may be hanging around.

When you do your water pump (may be a red herring, i'd expect it to fail by leaking or having a rough / seizing bearing) you can drain the coolant again and see how it looks.. any extra crud that comes out should settle in your drain bucket/ bowl and the coolant should be reusable. If there is crud then keep flushing before refilling, and maybe add another shot of coolant flush while doing it just to be sure.

Of course you could be observing a genuine effect of the rad / stat opening, but I'd say it's normally not noticeable unless you were really looking....

yea nice new coolant in it, drained it all again for the stat change then filled with just water, took for a test drive and seemed to be doing it more often but today as i was flushing the oil system waiting around for it to do its job i thought i would replace the water with the proper mix of anti freez and water and relised the cap wasnt done up tight emptyed the lot again and it was crystal clear so refilled with anti freez/coolant mix roughly 50 50. oil flushed and filled back up with new oil + filter, im getting the air filter tomorrow. Cam belt soon and when thats done i will feel comfertable in giving it some wellie to see what its made of

when you say "unless your realy looking" my eyes are flicking to it prety often and it does kinda settle down when fully up to temp, when stopping and starting in traffic it goes to the 2nd marker over half way mark and the fan kickes in and it goes down again but not as quick as when its warming up. maybe its fine, maybe it is the pump but the engine purrs and theres no rattling or grinding so maybe the pumps fine.
its not normal as far as im concerned ive had quite a few cars and this has never happend, they get to temp and stay there or keep going and boil over never realy up and down unless theres issues with head or cooling system... but all seems fine... im still a little stumped on it, water pumps are around £60 so do i replace or not is what im asking my self.

sorry bout the long winded text, still buzzing from cola and coffee:slayer:

 

[bluejohn125]

Okay I checked my car yesterday to see how it behaves on warmup, and I think what you're seeing is actually normal... Car is 1.2 Brava that had cooling system overhauled last year (comprehensively flushed, new heater matrix, good new antifreeze 50%).

Start car, heater off, drive about 2 miles semi-urban up to roundabout... Engine temp rises slow and steady to 1/2 notch ABOVE normal.

Move off, temp dips to 1/2 notch BELOW normal, so stat has opened and cold rad coolant now entering warm engine block.

Drive on, temp rises steadily and settled BANG ON normal, turn on heater, no change in temp, carry on like this.

So realistically since say if maybe 2/3 of the coolant is in the rad, you have to expect a temp dip when this starts flowing. That was a problem with the early Rover K-series engines.... cold water suddenly dumped on hot cylinder head... bye bye gasket. They had to add a little bypass hose or port so that a bit of rad coolant was always circulating during warm-up.

So by my reckoning you're good to go, just make sure all your filler caps are on properly! Oh and it's a bugger to correctly check your coolant level looking halfway down the tank inside the rad isn't it!