ifloochies

Coolant boiling in expansion tank - 1.6 Sigma NA

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Revisiting the water pumps, is it possible the impeller could be coming loose off the shaft when it/coolant temperature rises.

Strange thing is, with the thermostat removed, I have observed that coolant coming out of the bleed port at the top of the radiator drops from an intense jet to a steady stream as the engine warms up.

Just want to rule out everything before having to go remove the pump and tamper with timing.

Aside the usual mode of pumps leaking, I haven't as yet read anything of such sort ever been experienced by anyone.

I guess there's a first time to everything, just want to be sure its not anything else first.

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Update:

Pulled off the water pump and there doesn't appear to be physically wrong with it.

The impeller is plastic and doesn't appear to have any erosion damage.

Still ordering a replacement, because at this stage I figure I have nothing else to lose.

Pouring water down the top hose, it pours out through the side of the block uncovered by the water pump, which rules out any blockages in the block/head.

Hope changing the pump solves it, otherwise I've got nothing else to do to it.

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As said before, initially assumed it would be a blockage in the radiator, but when I had that off, I could hose it right through. Strange thing is, from startup, coolant flow seems to be normal, and as it warms up flow would gradually drop off in both the main circuit as well as the bypass. Keeping the revs up above 2.5K seems to keep everything working as it should, and the moment I let off, in the time it takes me to get from the driver's seat to the front of the car, the coolant level would start to rise in the expansion tank.

Even though a test for combustion gases in the coolant came out negative and the engine ticks over smooth and quiet, I'm starting to wonder if I may be having problems with the cylinder head or something - no bubbles to be seen in the expansion tank though, just looks like coolant is not getting pushed around to effect heat exchange.

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Update:

Changed the water pump and no joy yet😕

Still looks like somehow coolant is not moving around; sitting in the block until its brought to a boil.....at this stage, I got nothing else.

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I have very same problem with my 1.6 duratec. Water in the cylinder head boils and pushes coolant out of the expansion tank. However temperature gauge shows normal (faulty temp sensor?) and the fan is not working. Top hose gets hotter than the bottom and radiator gets hot but maybe not hot enough compared to the top hose.

As you said leaving the thermostat out lets it run OK, is that an option to live with? My guess for your problem and maybe mine, is restricted flow through the radiator hence at idle not enough coolant is getting pushed through the rad.

BTW anyone know how to debug the fan; it is not coming on with air con either. I don't seem to have any volts down at the fan.

 

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13 hours ago, ifloochies said:

Update:

Changed the water pump and no joy yet😕

Still looks like somehow coolant is not moving around; sitting in the block until its brought to a boil.....at this stage, I got nothing else.

 

58 minutes ago, EdGasket said:

I have very same problem with my 1.6 duratec. Water in the cylinder head boils and pushes coolant out of the expansion tank. However temperature gauge shows normal (faulty temp sensor?) and the fan is not working. Top hose gets hotter than the bottom and radiator gets hot but maybe not hot enough compared to the top hose.

As you said leaving the thermostat out lets it run OK, is that an option to live with? My guess for your problem and maybe mine, is restricted flow through the radiator hence at idle not enough coolant is getting pushed through the rad.

BTW anyone know how to debug the fan; it is not coming on with air con either. I don't seem to have any volts down at the fan.

 

For the fan, first checks are fuse and relay.

The bottom rad hose should be cooler than the top, that shows the stat is open and the radiator is doing it's job of cooling the coolant between the top and bottom hoses.

I must admit I'm stumped now though.  If leaving the stat out is working for both of you then it seems like a stat problem.  Not opening far enough maybe?  You should be alright running without the stat at this time of year but not when we get to winter, it'll never warm up and you'll have a good chance of warping things as well as wasting loads of fuel and probably failing MOT emissions as well.

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How is anything going to warp because a thermostat is not installed? I think the only downside in winter would be a cool heater and less mpg. Generally I would expect the engine to be under less stress without a thermostat as the temp cycling takes longer.

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So starting to look like the engine might be toast. Started to overheat again even with the thermostat removed.

The entire surface of the radiator gets hot in time, but I constantly have gas/steam purging from the bleed port at the top of the radiator.

Have tried bleeding the system multiple times by filling it from the top radiator hose as well as tried vacuum filling it with a vacuum pump, but still made no difference at all.

Starting to think I may have a crack somewhere in the head that's pressurizing the coolant or causing it to boil off inside the engine.

 

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Any smell of coolant in the exhaust?  Sludge/foam on oil filler cap or coolant bottle?

I think there’s also a test kit to see if there’s exhaust gases in the coolant. A decent workshop should be able to check that for you. 

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Nope, no smell of coolant in the exhaust, and no mayo under the oil filler cap in the coolant bottle.

What happens is it would start to boil over even with the fan running and temperature sitting at 105 degrees C, open the bleed plug at the top of the radiator and a whole lot of gas/steam pours out for a few seconds before actual coolant starts coming out of it.

The moment coolant starts to come out of this orifice, cap it off and the temperature starts to drop and the fan soon stops, meaning this gas was inhibiting coolant flow.

It would run for about 2 to 3 minutes at which time it would happen again.

So have changed just about every part of the cooling system but still have this problem.

So what now, change the cylinder head or replacement engine on the cards?

 

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On 8/8/2019 at 7:07 PM, EdGasket said:

How is anything going to warp because a thermostat is not installed? I think the only downside in winter would be a cool heater and less mpg. Generally I would expect the engine to be under less stress without a thermostat as the temp cycling takes longer.

Because you'll be driving on a cold engine for longer, this is what causes the hot spots which warps things.  You want to be driving carefully until the engine all warms up together before any 'abuse'.  Of course you could just drive carefully everywhere, but you will inevitably have to accelerate onto the motorway or for an overtake fairly often...

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18 hours ago, ifloochies said:

Nope, no smell of coolant in the exhaust, and no mayo under the oil filler cap in the coolant bottle.

What happens is it would start to boil over even with the fan running and temperature sitting at 105 degrees C, open the bleed plug at the top of the radiator and a whole lot of gas/steam pours out for a few seconds before actual coolant starts coming out of it.

The moment coolant starts to come out of this orifice, cap it off and the temperature starts to drop and the fan soon stops, meaning this gas was inhibiting coolant flow.

It would run for about 2 to 3 minutes at which time it would happen again.

So have changed just about every part of the cooling system but still have this problem.

So what now, change the cylinder head or replacement engine on the cards?

 

I really wouldn't recommend opening the bleed point at 105c! :unsure: 

The test for combustion gasses mentioned above is a sniffer test, but I think you've already had that done earlier in the thread right?  A crack in the head should show up in this test.

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