Slightly overheating

[endless_punk]

Ok, well my story starts a couple of weeks back when I was on my way to palmy. Cruiseing along in my AE101 Levin when I start to hear this rattle then I see the temp gauge flying up and steam coming out of the bonnet. The rattle I could hear was the radiator cap that had flown off the radiator and landed next to the throttle bodies. Now I'm pretty sure I had put the cap on properly before I checked the water coz it made it over the Rimutakas no hassles. So first question: What could have caused it to fly off??

Anyways, I let it cool down and filled it up again and nursed it to Palmy. It was then that I found it was running a bit warmer than usual. I've got it back home and changed the radiator with a new one (well 2nd hand) but it is still running warm, just over half way. I use to always run under half, more so quarter way before the cap came off. So what could be the problem?? Could it be a blown head gasket, or something else?? It seems to go through the water quiet a bit, I need to top it up once a week or so.

Sorry for the long winded description, but any help would be great!!!!

[Silent Knight]

Does your oil look milky at all? If it doesn't then I don't suspect it will be a BHG so that will rule one thing out......

[kingcorolla]

Changing the cap would do close to nothing if your car is running hotter. The radiator caps function is to control cooling system pressure, not heat. The thermostat controls the heat My bets on that, insuring your cap is the correct pressure rate..


Also, thers nothing better for a cooling system than a good reverse flush, also the flushing radiator. Does wonders. easy to do, Takes a socket set, pliers, hose, air compressor (if poss) Take you 1-2 hours in the weekend.

[Adamal]

He said he changed the radiator, not the radiator cap!

I'd do what Silent Knight has said. Rule of thumb, if you're loosing water, check your oil for milky cream colour substance. If you're loosing oil, check your radiator for milky cream substance.

Had an old 85 Sunny (I STILL miss that car!) that was loosing lots of oil. Checked the radiator and found a milky cream mix in there. Oil and water don't mix, right? Well they do under pressure! That cream coloured liquid is what the end result it.

It can mean 2 things.
The most common thing is that you've blown a head gasket and the water/oil is passing through to the other jacket.

The less common one is that you've cracked your head between the oil and water jacket feeds. You haven't been thrashing it while its cold, have you? Thats one thing that can cause that.

As to what could have actually made the cap fly off in the first place.... Not too sure on that one. Other than it wasn't done up properly in the first place. Theres typically 2 "clicks" to a radiator cap. When you put it on, the first one holds it in place, but with hardly any pressure. The other one is fully on and for normal operating conditions. You'd only use the half on one if you had like a split hose or something and didn't want the cooling system to pressurize.

[BZG Wagon]

Check the simple things first:
1) Thermostat
2) Pipe Blockages
3) Any split pipes / other leaks (Frost Plugs?)

Then,

4) Head Gasket
5) Waterpump

- Get a pressure test, most raidator places will do them for free.

[[V8ROLA]]

if it is pressurising the cooling system it will most likely be the thermostat as it will be staying shut and causing the water to boil. and when you top it up make sure you bleed your system (make sure your heater is on hot and the best way is to remove one of the heater hose's and flush it threw there as it goes threw the whole system) or you will get air pockets in the system and it will cause it to over heat aswell.
another way to check if it is the thermostat is to let it go dead cold, run it and keep checking the top and bottom radiator hose's and see if they both are getting hot, if they dont then yes it will be the thermostat if they do get hot then look else where for props, get it pressure tested, head checked etc.
as for the cap popping off if it was only on one click then it wont pop off as it wont let the pressure build up in the system cause it is not sealed.

[fangsport]

if the head gasket has blown between the cylinder and the water jacket there will be no oil in the water or vice-versa. the water will become pressurised from the cylinders and blow the radiator cap or hose.

take your waterpump drive belt off and get the engine up to temperature with the cap off, if the are a lot off bubbles in the water then chances are you have blown the gasket .

[B18CPOWER]

My guess would be to add more antifreeze to your coolant. Raises the boiling point of the water and will make it run cool again.

[endless_punk]

Well the oil/water doesn't have a any tinge of white to it so that could be a really good thing ie not a blown head gasket.
How do I check if the thermostat is the problem??
Cheers for all the help

[Silent Knight]

Well the oil/water doesn't have a any tinge of white to it so that could be a really good thing ie not a blown head gasket.
How do I check if the thermostat is the problem??
Cheers for all the help

get another one and test it against the old one from your car

[fangsport]

take the thermostat out and put it in a cup of boiling water. if it dosn't fully open it is rooted and needs to be replaced.

if your pressure cap was blown off, then chances are the gasket is blown as the air from cylinders is not only under pressure but also the heat turns the water into steam which has up to 17 times the volume as when it was water, further pressurizing the system.