WTF! Why?

[... rick]

Not 4x4 tech, but tech all the same.
The missus' Ford AU XR6 is having cooling issues.... sort of. About 6 months ago I replaced the radiator as the old one had cracked a plastic side tank. Put a twin row copper core job in its place.
All was good up until a few weeks ago, we were having to top up the coolant every week or so, usually about 1.5-2 litres.
What is happening is the overflow tank (where you fill it from) is boiling and overflowing, but (and this is the weird bit) according to the temp gauge, the car is not overheating.
So, I went and bought a new thermostat this morning and fitted it, started the car, topped it up, and sat and waited till the car got hot enough for the thermostat to open, so the coolant level would drop and I could top it back up. Basically, the level never dropped (indicating to me that the thermostat didnt open - it was rated to 91*) and the overflow eventually boiled.
Any idea WTF is going on?
Im now waiting for it to cool down, then i am going to reverse flush it from the thermostat end back to the overflow to make sure there are no blockages, then I am going to replace the thermostat with a Tridon, as well as a new rad cap.
Anyone got any other ideas?

Cheers guys.

PS - Burning it is not really an option.

[Tomo_89]

mate i would try a new cap also make sure the line from the over flow bottle to the rad. isnt blocked.

[nastytroll]

if there is a hole or bad seal in the hose from rad to overflow it will push hot water into the overflow and suck air back when it cools.

[simkell]

I would cut the center out of the old thermostat and put that in. Then run a clear hose from the top of thermostat housing and run it up towards the top of the bonnet. fill the system and start it up. if fluid tries to push up the clear hose then your water pump will be working, if not then your pump is cactus.

to me it sounds like there is no flow. if the top and bottom radiator hose are of the same temp, then coolant isn't flowing. assuming the radiator is fine, then i would be looking at either the thermostat or water pump. Also are you sure your gauge is working? Are your fans kicking in?

[bazooked]

i was going to say water pump as well but ya beat me to it, these have been known to play up and cause problems.

[Chops_69]

Blown head gasket is one possibility there aswell make sure your thermostat has a little maybe 2 mm hole in the flat plate part or it may have one there with a little plastic ball thing to block it off they need that to bleed the cooling system also check all your hoses are clear expecially the 10mm ones that goto the tank blow air through em!

[SIMMO84]

X2 on head gasket, very common on fords.But try the easier things.

[chimpboy]

I would have guessed lack of pressure, not water pump. ie, you need a new pressure cap.

If it were a blocked thermostat then the coolant in the radiator and overflow bottle would just stay cool.... I think.

[SIMMO84]

I would have guessed lack of pressure, not water pump. ie, you need a new pressure cap.

If it were a blocked thermostat then the coolant in the radiator and overflow bottle would just stay cool.... I think.

I have driven an earlier ford 6 about 300kms with out a radiator cap (by accident) and didnt have any problems at all. No radiator cap will only cause problems when th ecoolant reaches its boiling point. I know this engine is pushing coolant out like it is boiling but from the description it sounds like combustion gasses from the engine is being pushed into the coolant and acting like it is boiling.

[mhgill]

Head Gasket I'd say.

[-Scott-]

I don't know if this is relevant to your situation, but:

I've converted my Sigma to EFI, so the inlet manifold is different, and the coolant path too. When I first fill the radiator it overheats and/or pushes coolant out. If I top it up while the engine is hot (cap off, engine running) it's fine from then on.

I guess there's a pocket of air getting trapped somewhere which overheats and expands. Once I've got that out, it's fine - if anything, it runs too cool.

What you're describing sounds similar to my problem? But I only have the overflow once.

[SIMMO84]

Make sure the heater is on when you try it next and with the tridon thermostate I wouldnt trust it. I ve got one in my VT commodore and 3 times now it has over heated when standing still and then been fine afterwards and I believe it is the thermostate sticking.

[chunks]

The Au's run a metal shim type headgasket and don't have anywhere near as many problems as the older models. Make sure you fill the cooling system completely before you start the engine, I've had many a Falcon get an airlock while bleeding the cooling system. The thermo fans will come on but they won't be blowing hot air so there is no circulation through the system. If you've put an el cheapo thermostat in it may not have a jiggler to stop air getting trapped under it. As said, drill a small hole in it to let any air pockets escape. The heater taps on Falcons also get all corroded and jam closed so check that too, it's under the inlet manifold near the firewall.

[pinkfloyddsotm]

Not 4x4 tech, but tech all the same.
The missus' Ford AU XR6 is having cooling issues.... sort of. About 6 months ago I replaced the radiator as the old one had cracked a plastic side tank. Put a twin row copper core job in its place.
All was good up until a few weeks ago, we were having to top up the coolant every week or so, usually about 1.5-2 litres.
What is happening is the overflow tank (where you fill it from) is boiling and overflowing, but (and this is the weird bit) according to the temp gauge, the car is not overheating.
So, I went and bought a new thermostat this morning and fitted it, started the car, topped it up, and sat and waited till the car got hot enough for the thermostat to open, so the coolant level would drop and I could top it back up. Basically, the level never dropped (indicating to me that the thermostat didnt open - it was rated to 91*) and the overflow eventually boiled.
Any idea WTF is going on?
Im now waiting for it to cool down, then i am going to reverse flush it from the thermostat end back to the overflow to make sure there are no blockages, then I am going to replace the thermostat with a Tridon, as well as a new rad cap.
Anyone got any other ideas?

Cheers guys.

PS - Burning it is not really an option.

someone has to say it ... sell it and buy a VE SS

[coxy321]

Head Gasket I'd say.

x356

How many km's has it done?? From previous experiences, i've found them to pack up around the 200-250,000km mark.

[-Scott-]

PS - Burning it is not really an option.

I used to work with an ex-Navy bloke who was trying to upgrade his E(something) Falcon. As a trade-in, he couldn't get much over $2k - but it was insured for $10k.

It burst into flame while he was driving it. Completely destroyed, in broad daylight in Brisbane.

He was demolition diver in the Navy - had nothing to do with the accident, of course.

[Eddy]

There is a little hose under the intake manifold near the firewall. It is common for this to develop a pin hole, and gradually get larger. I've had this one let go on me several times, and on one car caused BIG overheat, warped head, nil oil pressure etc.
Check this one as the symptoms you describe match perfectly.

[Luxo]

Hey mate, It could very well be a head gasket issue but its not likely on the Au onwards. It does happen but nowhere near as coomon as the E-Series. If you run the engine with the radiator cap off does it push water or bubbles out through the cap? While you are there make sure the coolant is circulating to ensure the waterpump is working. Make sure you run a genuine thermostat with a 3mm hole drilled in it opposite the jiggle pin. Also fit a brand new radiator cap if not already. When filling the cooling system run the engine and remove the small hose from the thermostat housing. Keep filling until it stops spitting air out of the outlet on the thermostat housing and refit the hose. If you are not ridding the system of air it can cause over heating, unsteady temp gauge and also allow the coolant level to drop as the air will turn to steam and be forced out of the oveflow.

If the problem still persists have the system both pressure tested and CO2 tested. Generally a headgasket issue with symptoms you describe will aslo exhibit a misfire or force exhaust gases out of the overflow from startup. We have had cars that bad at the worshop ( usually daihatsu's) that they wont run without removing the cap first! If yours does not do this then It sounds more like you have air pockets throughout the system.

[V8Patrol]

PS - Burning it is not really an option.

I'll happily lend you my lighter

[NutterGQ]

As said above AU not prone to bust head gaskets as it uses a revised metal headgasket, is the car on LPG?

[RUFF]

If its boiling in the pressure tank but the guage is saying its not hot. You have an air pocket right where the temp sender is or its got no water in it. A temp sender does not work if it is not in water. Steam or hot air will not read on your guage.

[... rick]

Finally got the system to burp late yesterday afternoon, so far has been fine. Fingers crossed!!

[ajsr]

if it persists rick i'd plug a scan tool into it and check the sender and make sure the thermo's are kicking in properly and at what supposed temp acording to the computer and then check that this is really correct.
also piss of that tremostat and run a ford one
cheers andrew