Technical Coolant issues, bleeding etc

[johntom]

Hi
Ive noticed my daughter’s recently acquired 2010 1.2 has the cooling fan coming on during short journeys. On inspection yesterday the coolant was below the min mark so I have topped it up (inc removing both bleed screws- bubbles from the rear one). I have checked the level this morning which is higher than the max mark (I could have overfilled as the filler tube isn’t transparent) however when I remove the bleed screws nothing comes out - this seems strange could there be a blockage ?

I also changed the oil yesterday, no sign of water contamination and no oil in the water, should I be worried about the head gasket on a 50,000 mile car ?

 

[jrkitching]

should I be worried about the head gasket on a 50,000 mile car ?

Mileage has little to do with it. HG failure is normally associated with overheating; if this happens, the HG will likely fail, irrespective of whether the car has run 50 miles or 50,000 miles.

The 1.2 has a good reputation for reliability, but the HG is known to be vulnerable if run seriously low on coolant. Often the HG will fail before the overheat is sufficient to register on the temperature gauge. Unfortunately leaks are not unusual; the bleed screw on the heater hose being a common failure point.

For these reasons, regular coolant checks are important on this engine. Other symptoms include failure of the heater to deliver hot air when selected, and gurgling noises behind the dashboard. If either of these happens, stop the engine as soon as practicable and check the coolant level.

From what you've posted, it appears you have caught the low coolant level in sufficient time to avert HG failure, but keep a close eye on the level. It may drop again for a couple of cycles as the system will self bleed, but it should soon stabilise. If it doesn't, you have a leak, which should be investigated and rectified as a matter of some urgency.

Also it is important to top up only with the correct coolant; the aluminium radiator core in particular is vulnerable to corrosion and subsequent leakage if there is too much water in the system. If you must top up with plain water in a dire emergency, then at the first opportunity either add an equal volume of coolant concentrate, or (better) change the coolant.

 

[Hilux phil]

Jack sent me this link which I found helpful for when I done my daughters timing belt and changed the water pump, took a couple of days for level to settle down and get round the system I found.
http://4cardata.info/elearn/312/2/312000000/312000000/312000003/312000484

 

[johntom]

Thanks for the replies,
I’m going to try bleeding again as there isn’t coolant visible when I remove the rear bleed screw (with the engine off ) surely if the coolant pipe is full there should be unless airlocked ?

 

[jackwhoo]

Thanks for the replies,
I’m going to try bleeding again as there isn’t coolant visible when I remove the rear bleed screw (with the engine off ) surely if the coolant pipe is full there should be unless airlocked ?

For water to come out of hole water level elsewhere in system has to be higher than the hole.


Remove bleed screw completely and make sure hole clear with a gentle probing if you are not sure.

It boils down to you have to overfill expansion tank on side of rad to get water out of bleed holes.

 

[johntom]

Hi
Yes I thought where I had the car parked the level of the filler neck was slightly higher than the holes - obviously not !
I’ve now parked the car nose up and coolant is present as expected. I will check the level regularly and monitor for any loss, I have a HG test kit I will try when I can find it, just to be sure.
Thanks again your replies

 

[jackwhoo]

Hi
Yes I thought where I had the car parked the level of the filler neck was slightly higher than the holes - obviously not !
I’ve now parked the car nose up and coolant is present as expected. I will check the level regularly and monitor for any loss, I have a HG test kit I will try when I can find it, just to be sure.
Thanks again your replies

No problem.

You are not the only one to find it awkward.

I really dislike expansion tanks that don't show the level in the system.

I do like header tanks where the level in the tank is the level in the system.

As hilux Phil days keep an eye on it for a few days and you will be sorted.

 

[jrkitching]

Don't overcomplicate this; the system will self bleed over a few engine cycles if you keep it topped up to the maximum mark. Fill the expansion tank to the maximum and run the car until it's fully warmed up. Don't fill above the maximum as this risks coolant being blown onto the road as the engine heats up. The level may drop after it's cooled; unless you've got a leak, this means it's purged some air from the system. Refill to the maximum & repeat; it should settle down after a few days. As others have said, there's no certain way to get all the air out first time and we all struggle with this one.

The bleed screw in the heater hose is flimsy, easily broken and prone to weeping. As the system will self bleed without it over time, there's perhaps something to be said for putting it in with a dab of suitable sealant and then leaving it alone. It never seems to be much use when it comes to getting the air out anyhow.

The bottom hose connection is equally flimsy and it's easy to break something when disconnecting the hose. On models with the integral expansion tank at the side of the rad, you can get just as much coolant out by syphoning or vacuuming; you can get a suitable hose right down to the lowest point in the end of the bottom hose. However you do it, you're likely to leave at least a litre behind in the heater circuit, so there's no point obsessing about getting out the last drop. If changing a water pump or thermosta and you're not due a coolant changet, you only need to lower the level below the relevant component and if you use clean utensils, you can put what you've vacuumed out back in at the end of the job.

 

[jackwhoo]

In Systems with header tanks any air in the system will eventually make it's way to the highest point , the header tank.

Your system has an expansion tank on the side of the radiator. The level in the tank doesn't even show the level in the radiator(let alone the rest of system) as the tank only has a tube at the bottom of tank connecting it to the bottom of the radiator.
That is why fiat fitted two air bleed screws.

There is no way for air trapped in the cooling system to self bleed it's way into the expansion tank.

Do what Phil did his system is the same as yours.

After filling system as best you can , reduce level in expansion tank to high mark, it's not good to over pressure system by not leaving expansion room.

Bleed screws just do up finger tight it's all they should need, if necessary get a new rubber washer.

 

[jrkitching]

There is no way for air trapped in the cooling system to self bleed it's way into the expansion tank.

You'd think it wouldn't, but it does. I've seen it happen loads of times.

I'm unsure of the precise mechanism, but it may be that the design of the bottom of the expansion tank acts as an air separator - the coolant flows directly underneath it.. Remember that at operating temperature, the flow through the cooling system is extremely turbulent, and at least some of the entrapped air will mix with and circulate with the coolant.

Another thought: at operating temperature, any trapped air will contain a significant amount of water vapour. I'm struggling to remember enough physics to work out the implication of the law of partial pressure, but I'm thinking any gas in the system will expand, causing the pressure relief valve to vent the vapour (air +H2O) to relieve the excess pressure. When the engine cools, the water vapour will condense, drawing coolant in from the expansion tank. This process repeats each time the engine cycles between hot & cold, removing a percentage of the air each time.

If anyone can come up with a better explanation of why it works, I'd love to hear it, but it's beyond doubt that it does.

 

[typecastboy]

Start the engine, remove the bleed screw completely and remove the filler cap. Slowly add coolant and watch the bleed hole. Eventually the air will get pushed round and coolant will come out if the hole. Replace the bleed screw, run for a few minutes with the cap off and then replace. You may hear some gushing coming from the passenger footwell. After a couple of days it will probably settle down and the air will be expelled into the top of the filler cap. Release the filler cap and top up if necessary.