Boiling over / expansion / catch tank woes....

[BERGS2]

not wishing to reopen this can of worms...but:

driving back from southampton yesterday - I reached the top of the M3 (the bit where it hits all the traffic & roundabouts on the A316...) after 5 mins or so of sitting in traffic I heard a horrible mechanical gurgling sound from under the bonnet and the temp guage shot up into the red..... i though to myself - luckily there was a car park just round the corner so I limped there and shut down the engine.

Bizarrely I felt the gurgling through the brake pedal - so I thought it was something much worse (the catch tank being mounted next to the brake servo)

Now - the pressure cap on my car is mounted on the catch/expansion tank rather than the swirl tank - though I am aware that this is a source of some debate I have never had any problems with overheating before - so I just left it there...

the swirl tank is always two thirds full and the temp used to stay rock steady at just under 90 degrees.

the speed at which the guage shot into the red would lead me to believe that there may be an intermittant fault with the thermostat - either that or there may be some air trapped

anyone got any advice?

what was the final word on the pressure cap anyhow?

[M@H]

..partially blocked radiator leading to reduced circulation under idling conditions..?

or

Did the fan come on..? (if not, a corroded connector)


Cheers,
Matt.

[BERGS2]

M@H said:

..partially blocked radiator leading to reduced circulation under idling conditions..? or Did the fan come on..? (if not, a corroded connector) Cheers, Matt.

yeah - fan was good when I resarted after letting it cool of for half an hour or so...

came in at 90ish as usual...

blocked rad.... sound like a bugger to test for!

[WildfireS3]

When mine was overheating I did the following:

Took the pressure cap apart to pieces so the spring actually depresses when on the Swirl tank. Added a new rubber seal to this.

Then I found that the tube from the expansion tank to the swirl tank was blocked. Unblocked this and all is good.

[M@H]

BERGS2 said:

M@H said: ..partially blocked radiator leading to reduced circulation under idling conditions..? or Did the fan come on..? (if not, a corroded connector) Cheers, Matt. yeah - fan was good when I resarted after letting it cool of for half an hour or so...

Thats different though.. could you hear it at the time of the overheat..?

Cheers,
Matt.

[andyf007]

My pressure cap is also on the expansion tank. I would not have thought though, that, in that configuration, the swirl pot should have any air in at all.

I always make sure that the swirl pot is full to the top, before replacing the cap and then fill the expansion tank half full. Any air developing in the block should rise to the top of the swirl tank and then travel along the pipe to the expansion tank, being replaced by water from there, in a sort of closed system.

Also, if the level of water in the swirl pot drops below the level of the top pipe from the thermostat housing, then you risk getting air back into the block.

I would check that the water is flowing freely from the expansion tank to the swirl pot first. To clear most airlocks, take the cap off the swirl pot and start the engine. Let it run up to temperature and ensure that the swirl pot is kept full, especially at the point where the thermostat starts to open and that the heater is on. Rev it a bit to get the pump working too. Then switch off the engine. There should be a bleed for the rad on the nearside top corner, check for air locks there too. Once done fill the swirl pot and replace the cap.

Andy

>> Edited by andyf007 on Monday 10th May 12:17

[BERGS2]

andyf007 said:

My pressure cap is also on the expansion tank. I would not have thought though, that, in that configuration, the swirl pot should have any air in at all. >> Edited by andyf007 on Monday 10th May 12:17

hmmmmm..... whenever I fill the swirl after a short run its back down to two thirds full again...

anything over this seems to get blasted out -

[andyf007]

BERGS2 said:

andyf007 said: My pressure cap is also on the expansion tank. I would not have thought though, that, in that configuration, the swirl pot should have any air in at all. >> Edited by andyf007 on Monday 10th May 12:17 hmmmmm..... whenever I fill the swirl after a short run its back down to two thirds full again... anything over this seems to get blasted out -

But it should expand the water up into the expansion tank and blast it out from there when the expansion tank is full or overpressured , does it?.With a closed system the swirl pot should only get air in if the expansion tank runs dry, so check for leaks too (include the heater matrix).

This is sounding a bit like a head gaskets gone, though . You could test for that by leaving the cap off the swirl tank and starting the engine, etc. DO NOT HAVE YOUR HEAD OVER THE SWIRL POT WHEN TRYING THIS! If a gasket's gone it will blow water out of the top of the pot. Normally you should be able to run the engine up to 90 with the swirl cap off and only get a small displacement caused by the water heating up.

Andy

[greenv8s]

Sounds like a typical overheating scenario. These rubber sealed pressure caps don't work very well, the rubber sticks to the metal and doesn't release until the pressure has gone past the nominal blow-off pressure, then is it comes unstuck it blows off suddenly dumping a load of pressure. Normally, the heads will boil at this point pushing a load more water out and replacing it with steam. Since the water pump can't pump steam the cooling system basically stops working at this point and a hot engine will overheat in seconds.

I strongly suggest you fit a new pressure cap after the old one has blown, they are reusable in theory but not in practice. Also investigate why the car boiled. Could be the fan stopped working, could be you had air in the radiator (you need to bleed this a couple of times a year), could be the radiator itself has scaled up, the scale acts as an insulator and stops heat from conducting out of the radiator.

[Le TVR]

A typical 'air-lock' description there.
Where does it leak from if you lose a third so quickly? Overflow or elsewhere?

Swirl tank should be full.

At worst you could drain the system and re-fill (slowly!)

[mikee boy]

I suffered from erratic overheating for about a year and always assumed it was serious. Managed to cure the problem by buying a new pressure cap (fitted to the swirl tank) and running 25% antifreeze (helped find some small leaks as it dries sticky!!). It's fine now.

[aka Spike]

Took mine off to the garage after it had been under cover for about a year... always had overheating problems. Turns out the radiator was 70% blocked!
So they re-cored the radiator and *removed* the swirl tank altogether, saying it's actually not necessary on the Ford 2.9 V6.
Also recommended I use 50/50 water/antifreeze and I must admit, problem solved!

[joospeed]

altho adding antifreeze increases the temperature range of the coolant, it can inhibit the transfer ability of the coolant too .. so in summer use slightly less concentrated mixture and top up to strength again for winter .. the corrosion inhibitors are important to prevent internal corrosion so don't run with no antifreeze at all.
If you're using strong antifreeze to disguise a fault in teh cooling system better to get the fault sorted first.

[greenv8s]

aka Spike said:

So they re-cored the radiator and *removed* the swirl tank altogether, saying it's actually not necessary on the Ford 2.9 V6.

Sounds a bit dodgy to me. You need a decent de-gas system which invariably means passing some of the flow through a separation tank of some description - in our case the swirl tank. What did they replace it with?

[bridgdav]

Ar$e...

Just limped home from work...

The car overheated pretty rapid, same as BERGS2, the expansion tank was full when I started...

It is now blown over the road from B/Stoke to Tadley...

Looking back through this thread, is it as simple as replacing the cap..?

'15lb long reach'..??

What is the best way to bleed the system?

Steam, Steam everywhere... well coming out of the expansion overflow anyway...

[mikeo]

Mine did the same last week. Check the radiator as only the right hand side of mine was getting hot - the other half was stone cold. LeeBee's having the car for the weekend to give it a severe talking to !

[aka Spike]

greenv8s said:

Sounds a bit dodgy to me. You need a decent de-gas system which invariably means passing some of the flow through a separation tank of some description - in our case the swirl tank. What did they replace it with?

Um... nothing, as far as I can tell. I take your point about the de-gas though - don't really know anything about this sort of thing but it sounds logical.
Also noticed this morning, after the drive to work, a small greenish puddle under the car. I think I'll stop by the garage again and see what they say.

[Simon Brooks]

Had a similar problem after winter layup, temp gauge would slowly rise to well over 90 then drop like a stone, this repeated itself all the time engine was running. Tried flushing system both when cold and with engine running with no luck, finally removed thermostat completely for a few days, problem solved the stat had packed up working, replaced stat for a few quid (and bolts, old ones snapped!!!!! be careful)temp now sits at just under 90. Down side was that flushing system cleaned out sediment/rust which opened up a small rad leak, small can of rad weld solved this, everything now tickety boo.

[aka spike]

By the way... just had the thermostat removed and all problems appear to be solved. Just did four 3-hour trips in the blazing hot sunshine and it didn't overheat once (even when pushed). Hasn't lost any water yet either (garage did a pressure test, didn't find anything) but that's one to watch.