Boiling water when bleeding

[G43x]

Hi gents, im an old forum user who lost their password. im in need of some help.

My caddy 1600 bakkie is boiling water when try to bleed the radiator, new thermostat, had the radiator professionally cleaned and a new fan switch.

both hoses are hot, the water starts boiling, the fan doesnt come on with the cap off, but when putting the cap on it does, the fan then runs for longer than 5 mins, with the peugot fan switch no boiling and fan kicks in early, however i dont wanna use the peugot fan switch.

Any idea on what it could be? Please

[mk2-phreak]

Water pump?

[G43x]

Water pump?

Thank you, the water is flowing though, when I rev the car coolant in the bottle does move.

[VAG Fan]

To my knowledge, the MK1 is bled as follows.

Top up the coolant on the cold engine. Keep the cap off, but ready to close at any time.
Open the valve to the cabin heater completely.
Run the engine (e.g. fast idle) until the thermostat opens (you can see this happening when the level drops in the bottle).
Drop the engine speed to a normal idle, and keep adding coolant until no more is taken up by the engine. Make sure the reservoir doesn't run empty. Make it about half full.
Then close the cap and run the engine until the fan kicks in.
Then cool down the engine completely and top up the coolant as needed.

If you keep the cap off, it is normal for coolant to "boil" out of the reservoir before the radiator fan kicks in. This is precisely why you close the cap during the second half of the bleeding procedure.

The standard radiator switch is 92/87, i.e. the fan kicks in at 92°C and stops at 87°C. But if all else fails, I think there are lower ranges also available.

[G43x]

To my knowledge, the MK1 is bled as follows.

Top up the coolant on the cold engine. Keep the cap off, but ready to close at any time.
Open the valve to the cabin heater completely.
Run the engine (e.g. fast idle) until the thermostat opens (you can see this happening when the level drops in the bottle).
Drop the engine speed to a normal idle, and keep adding coolant until no more is taken up by the engine. Make sure the reservoir doesn't run empty. Make it about half full.
Then close the cap and run the engine until the fan kicks in.
Then cool down the engine completely and top up the coolant as needed.

If you keep the cap off, it is normal for coolant to "boil" out of the reservoir before the radiator fan kicks in. This is precisely why you close the cap during the second half of the bleeding procedure.

The standard radiator switch is 92/87, i.e. the fan kicks in at 92°C and stops at 87°C. But if all else fails, I think there are lower ranges also available.

Much appreciated thank you, I’ll try that!

[G43x]

Tried bleeding it. Fan comes on for 10 mins.

Top radiator hose feels like there’s pressure and “no water” in it.

[VAG Fan]

Truly 10 minutes? That's very long. I'm beginning to think you might have a blown cylinder head gasket, with combustion pressure and heat leaking into the cooling system. Any radiator shop should have a testing kit to confirm this.

Also, are you using coolant additive (at least, say, 25%), or only pure water for now? I ask because the additive not only stops corrosion, but also raises the boiling point.

[Ashveer03]

Water pump?

Thank you, the water is flowing though, when I rev the car coolant in the bottle does move.

That doesnt necessarily mean that the water pump is good. Water should be circulating at idle.

Sent from my CPH2371 using Tapatalk

[G43x]

Truly 10 minutes? That's very long. I'm beginning to think you might have a blown cylinder head gasket, with combustion pressure and heat leaking into the cooling system. Any radiator shop should have a testing kit to confirm this.

Also, are you using coolant additive (at least, say, 25%), or only pure water for now? I ask because the additive not only stops corrosion, but also raises the boiling point.

Yes 10 mins, but this was caused by a cheap fan switch, bought one at Goldwagen today and fan doesn’t run longer than 1 min.

[VAG Fan]

Up to 1 minute is perfectly normal.
BTW, some pressure in the pipes is also normal. At operating temperature, they shouldn't be rock hard, but can be quite stiff.

If your radiator fan is cycling, at idle, between
... on for about 30 s to 1 min and
... off for about 3 to 5 min,
then the water pump is OK.

[G43x]

Up to 1 minute is perfectly normal.
BTW, some pressure in the pipes is also normal. At operating temperature, they shouldn't be rock hard, but can be quite stiff.

If your radiator fan is cycling, at idle, between
... on for about 30 s to 1 min and
... off for about 3 to 5 min,
then the water pump is OK.

Thank you, all seems to be 100s now.

I was under the impression there should be no pressure in the pipes, they a bit stiff but not near rock hard

[walidrek0011]

Have you checked the fan relay and wiring? Might be worth a look. Also, make sure the Peugeot fan switch is fully compatible. Airlock could be another culprit; try bleeding the radiator with the front raised slightly.

[VAG Fan]

All the Mk 1 1600s I've ever driven, didn't have a fan relay. Fan current is switched directly at the radiator thermo-switch.
Why would one check the fan wiring, if the fan is running normally?
Why would one check compatibility of the Peugeot switch if it's been replaced with one from Goldwagen, running normally?

[G43x]

Update:

I replaced the water pump, new head gasket, bolts and a skim.

The coolant is still boiling when trying to bleed it with the cap off

[mk2-phreak]

Is the car overheating when you drive?

[G43x]

Is the car overheating when you drive?

Nope it doesnt

[VAG Fan]

Why are you trying to bleed the boiling-hot system with the cap off? In my 30+ years of experience with Mk1's, it ain't gonna happen.
Like I wrote above, when the thermostat has opened and taken in extra coolant (without letting the bottle run dry), then the cap should be closed.

With the cap removed while waiting for the fan, even a properly bled system will boil over and possibly even re-introduce air.

[mk2-phreak]

Is the car overheating when you drive?

Nope it doesnt

So you don't have any problems. What are you trying to do?

[G43x]

From searching the forum multiple posts say you need to let the car run until the fan comes on to bleed it.

So I’m trying to figure out if I have a problem.

[VAG Fan]

You DO need to let the car run until the fan comes on.
But you DON'T leave the cap open until the fan comes on.
The cap is closed after the thermostat has opened and the system has taken in the second portion of coolant.
You then continue to run the engine (with the cap CLOSED and the bottle about half full), until the fan has cycled.
This last part of the bleed, with the cap closed, removes any last bubbles of air from the radiator (and other parts), while the system is under normal operating pressure, and hence, normal flow.

This removal of the last bubbles is why the coolant level often sinks slightly during that last step. Bubbles are removed by the coolant flow, and they accumulate in the bottle. That just doesn't work with the cap open.

[VAG Fan]

And just to re-confirm, because I've tried it myself on perfectly healthy Mk1's:
If you leave the cap open, then just before the fan kicks in, a whole lot of the coolant will boil out of the bottle.
That is not an engine problem, but an operator error.

[mk2-phreak]

From searching the forum multiple posts say you need to let the car run until the fan comes on to bleed it.

So I’m trying to figure out if I have a problem.

Lol. I give up