Technical 4x4 coolant bleeding.

[Albert Alfvag]

Hi.
Just a quick question. I drive a panda 4x4 1988 and as I understand it the 4x4s have a self-bleeding coolant system.
I just emptied the cooling system to change the metal coolant pipe in front of the engine.
The owners manual says the system holds 5,2 litres of coolant, but I've only put in 3l and even when I start the car the coolant level in the tank doesn't get lower (it's about half full atm).
Should I just drive and top up as necessary or should I do something else?
I don't want to risk overheating some part of the engine if there isn't enough coolant.
I havn't run the engine up to when the fan cuts in yet. Should I?

Thanks,
Albert

 

[bugsymike]

It may be that not all the old coolant came out, but I agree not something you want to leave.
In general terms I would check that there is water/coolant above and below thermostat if possible by slackening hoses to check, if water comes out I would then retighten hoses, run engine at idle whilst constantly checking water temp. and hoses around engine to detect a change in temp.
Usually the heater hoses will start to warm first and possibly the top hose coming from the thermostat going to the radiator , until the thermostat opens the bottom hose and the lower part of the radiator will remain cooler, once thermostat opens they should warm up and all hoses be at same temp.
Ideally after running for ten minutes or so at idle from cold the hoses will all reach the same temperature, roughly a little too warm to hold and your temp. gauge should reach normal.
With engine off but after running for ten minutes if you put hand on the two heater hoses they should both be equally warm if heater in hot position, if one is noticeably colder colder due to air in system, if VERY CAREFUL slacken the hose clip to the colder one (usually the highest) where it goes through the bulkhead towards passenger compartment, just enough to let a little air/water to escape to release any trapped air. The reason being is that the heater is usually the highest point in the cooling system so trapped air most likely there, which is an early warning of coolant problems when heater blows cold!
If you suspect engine is overheating DO NOT slacken any hoses as serious burns can happen!!!
A safer way of doing the last bit is to use a coolant pressure testing pump to imitate the normal engine coolant pressure to help remove any trapped air, but most people do not have access to one. If you do have one only pump to the pressure written on the radiator/coolant pressure cap, usually no higher than around 1Bar (14.7lbs) psi. otherwise you may damage the radiator and hoses etc.

 

[Albert Alfvag]

It may be that not all the old coolant came out, but I agree not something you want to leave.
In general terms I would check that there is water/coolant above and below thermostat if possible by slackening hoses to check, if water comes out I would then retighten hoses, run engine at idle whilst constantly checking water temp. and hoses around engine to detect a change in temp.
Usually the heater hoses will start to warm first and possibly the top hose coming from the thermostat going to the radiator , until the thermostat opens the bottom hose and the lower part of the radiator will remain cooler, once thermostat opens they should warm up and all hoses be at same temp.
Ideally after running for ten minutes or so at idle from cold the hoses will all reach the same temperature, roughly a little too warm to hold and your temp. gauge should reach normal.
With engine off but after running for ten minutes if you put hand on the two heater hoses they should both be equally warm if heater in hot position, if one is noticeably colder colder due to air in system, if VERY CAREFUL slacken the hose clip to the colder one (usually the highest) where it goes through the bulkhead towards passenger compartment, just enough to let a little air/water to escape to release any trapped air. The reason being is that the heater is usually the highest point in the cooling system so trapped air most likely there, which is an early warning of coolant problems when heater blows cold!
If you suspect engine is overheating DO NOT slacken any hoses as serious burns can happen!!!
A safer way of doing the last bit is to use a coolant pressure testing pump to imitate the normal engine coolant pressure to help remove any trapped air, but most people do not have access to one. If you do have one only pump to the pressure written on the radiator/coolant pressure cap, usually no higher than around 1Bar (14.7lbs) psi. otherwise you may damage the radiator and hoses etc.

Thank you for the very comprehensive explanation!
It all worked out in the end. I let the engine reach operating temp, squeezed the hoses a little and just changed parking space. And after that the expansion tank gurgled and I could fill in an additional two litres. I guess a little bit of movement and an open thermostat made coolant flow into the empty spaces.

Cheers,
Albert