V6 Overheating and bad rattles

[asustek]

My 1997 VT has been leaking coolant and overheating. Yesterday after work i was on my way home and the engine temperature started rising drastically i was forced to pull over and let the car cool down. Started the car again and went for a drive watching the temp again it rose. Found something out, only overheats really quickly if the aircon is set to hot. As soon as it is set to cold from H it drops really quickly to about half way.

Also, I've noticed that my car has a really bad rattle under load. I dont know where it is coming from engine or tranny?? It doesn't do it when I shift into neutral and give it a little rev but it does do it when I move the steering wheel from left/right. The rattle doesn't happen all the time - but when it does, gets progressively worse as I continue to drive the car.

When I turn the car off and take a look at the engine - I can hear a hissing noise, like there is a build up of pressure and the hose just wants to explode. Not good huh?

All this has started happening since I flushed the radiator.

Any help would be great thnx

[AttaBoy]

Well something is not right within the coolant system.

Did you bleed the coolant after the flush?? I assume the hissing sound means air in the system.

There is a bleeder screw on top of the thermostat housing. Unscrew that and let the engine idle and close the screw when coolant starts coming out. (The engine cover needs to come off to access the bleeder screw).

[pablo]

Do you have enough coolant in the system, no air pockets??
Did you bleed the air out from the top of the thermostat housing when you did the coolant change??

[Not_An_Abba_Fan]

Another vote for air in the system. Did you turn the heater to hot when you filled it up again? Did you change the thermostat? Is it in the right way around? If you didn't maybe the flush washed all the crap into it and it doesn't open properly.

[Noy]

Mate I had the same problem not long ago, only because I didnt bleed it properly.

[Clutchy]

When ya do bleed it let the coolent flow out abit befor you close it just to besure ya get all the air out and with the hissing try find were thats coming from as if the air can get out so can the water so maybe the clamp is not tight enough or something else ia amiss in there somewere good luck with it anyway mate.

[Not_An_Abba_Fan]

The hissing could be the radiator cap, steam is at a higher pressure so it will come out of the cap before water does.

[asustek]

Thanks guys yeah its been about 2 weeks since i flushed the system followed instructions from another thread on jc. Did turn on the heater to hot and ran the hose through all the channels. I had a feeling it was something to do with the thermostat and the bleeder. Havnt changed the thermostat yet as im currently running a barsleaks cleaning agent (maybe this stuff blocked the thermostat) through but i did play around with the screw didnt know what i was doing. So how do i bleed?? engine on, disconnect the hose from the top of the radiatior and turn the screw til water comes out then tighten again?

[accentstencil]

Don't undo anything. Run the engine till it reaches normal operating temperature and then slightly undo the bleeding screw and the air will come out. Tighten when only coolant and no air comes out. Repeat to make sure all the air is gone.

[asustek]

Nice i'll give that a go. First I'll have to fix the leaking radiator - found where it was leaking from. Is it worth going for a "high performance" aluminium radiator or are they just as good as the oem version?

[asustek]

You'll never believe what has just happened. Broken left engine mount what else could go wrong...

[dazza33]

Was having overheating problems for ages. I had tried everything, Pressure Test, Flush, Water Pump, Thermostat and new Radiator Cap, eventually broke down in the middle of nowhere the other weekend (on that really hot day) splitting the heater tap for the second time in 3 weeks. Anyway finally realised maybe this was a little out of my league, bit the bullet and paid Natrad to look at it. Basically boiled (pardon the pun) down to not bleeding the system properly when i did the work on it! Wasted a lot of money because i didn't do the job properly, before i do anything on the car now i always check the forum for advice and other's experience's.

[lout]

Drop into one of the radiator shops and ask them to do a pressure test of your system.
You may have a head / gasket problem. Is your main thermo fan working?, when you turn air con on the second fan will kick in. Also was the rattling when the engine overheated or could that have caused it to overheat, thinking of knock sensor