g60 pressure in coolant hoses/burst head flange

[Andy T 0]

The other day while sitting in traffic the coolant temp crept up to 115 degrees then steam rose from the bonnet. The front head flange had sprang two major leaks (a 3 month old item from Euro car parts, looks like it blew the seal on the 'plugged' bottom outlet) I also noticed that the fan wasn't running at all, and the radiator didn't feel very hot.

 

A few wks before this happened I'd noticed that the top coolant hose felt pressurised (not swelling but pretty firm) but the matrix hoses seemed fine. What could be causing the pressure in the top hose, a stuck thermostat? before the burst happened the running temps had been normal, and the system was flushed out and replaced with G12+ around 2 years ago.

 

This weekend I'm going to replace the head flanges & radiator fan thermo switch, should I be checking anything else/change the thermostat aswell?

[Riley 0]

does sound like either the thermostat or the water pump... :)

 

strange how its blown the sealed off part of the flange though,i think it should have vented through the expansion tank...which would mean that the cap is dodgy,may as well replace it while your at it.

 

and the blue ones are better. :)

 

neil.

[Andy T 0]

Good point I have a new 'blue' cap that I bought from AVS and forgot to fit it :roll:

[Andy T 0]

Started work on it this afternoon, the front head flange had cracked in two places in the main bore and was mis-shaped, I think I must of overtightened it when I first saw it leaking :oops: it had also cracked between the two sender housings. The plugged outlet looked fine so the leak must of been coming from the bore cracks. The one I fitted today is from GSF as opposed to ECP, the quality does look better especially the sealing face.

 

I also replaced the side water flange, the cyl head was quite pitted behind the seal so it must of been leaking for ages.

 

I Checked my Bentley manual, all water flange bolts should be torqued to 10Nm (7 lb ft) only, my torque wrench can't access those bolts so I torqued another M6 nut to 10Nm to get a feel for how much force is required (not a lot) then used a spanner.

 

I have been topping the expansion tank up every few weeks for last few months, could doing that introduced an airlock, and can airlocks cause pressure in hoses?

[Riley 0]

I have been topping the expansion tank up every few weeks for last few months, could doing that introduced an airlock, and can airlocks cause pressure in hoses?

 

you wont necesarilly get an airlock from topping up the expansion tank,as long as the coolant is still visible.but...a slight leak somewhere could take air in when the level is dropping etc...

 

air locks can cause pressure in the system,you would have very hard rad hoses(if the cap isnt working properly) and coolant p1ssing out through the expansion tank if it is working properly.

 

are you still having the problem then m8?

 

if so id disconect the overflow hose at the expansion tank end,and point it into the expansion tank.

start the car and blip the throttle by hand,just to check that the water pump is working.

 

neil.

[Henny 0]

the coolant system is designed to be pressurised... (0.8bar IIRC) Water boils at a higher temperature when pressurised...

 

With the leaks you had there, you're system becomes unpressurised as it warms up, this knock the temps up causing more the water to boil, release much more gas and over-pressurise the system...

 

Give it a go for a few days now you've fixed the leaks keeping a close eye on the temp gauge and the oil temps and see how it goes on... 8)

[Andy T 0]

I didn't finish it off, started doing other 'little' jobs in the engine bay then got rained off, will fill it up tomorow and test the overflow hose, good idea that mate.

[Riley 0]

no probs m8 :)

 

as henny says,the system is pressurised,but through heat/water expansion.an air lock would pressurise it in a diffarent way.

 

so with the overflow pipe,as the engine builds temp coolant would run out...but if you blip the throttle it will pulse out in relation to the rpm.

 

ps:have some coolant/water ready to chuck in,so as not to let the level drop below visible in the expansion tank.

 

neil.

[Henny 0]

oh, and check that your fan is coming on! Sounds to me like your rad switch has died... ;)

[Andy T 0]

Back on the road again, everything seems ok!

 

I checked the overflow pipe, it seemed to have a slight blockage so cleared it, ok now and water trickles out of it when the engine is idling. The bottom rad hose is hot when up to normal temp and with the new thermo switch the fan is coming on now at 95 deg. (probably never used to). There's no abnormal pressure in the hoses and the temp never rose higher than 95 deg. while driving or sat in traffic, cheers for the help guys.

[Henny 0]

8) Good to hear mate... 8)