Bleeding Coolant Circuit
Discussion
Shortly after I've worked out how all the new shiny pipes and blue hoses replace the rusty and perished things under the bonnet (replacement is not always as simple as the reverse of removal.... especially when you didn't take enough 'before' photos) I'll be wondering how to bleed the system.
Any tips? presumably the bleed valves on the pipes coming from the top of each engine bank have something to do with it?
Also, before I put it all back together I'd like to shove a hosepipe in one of these pipes and blast the whole system through - is this wise or am I going to upset the impeller blades in the water pump/cause other problems? Which way does the system 'flow'?
Cheers
Joe
Any tips? presumably the bleed valves on the pipes coming from the top of each engine bank have something to do with it?
Also, before I put it all back together I'd like to shove a hosepipe in one of these pipes and blast the whole system through - is this wise or am I going to upset the impeller blades in the water pump/cause other problems? Which way does the system 'flow'?
Cheers
Joe
Bleeding:
I fill the system with 50:50 mix with the rad bleed open.
Once this vents coolant close it off and open the 2 coolant rail pipes. Continue to fill.
Once they vent coolant close and top the system to the top.
Now start the engine with the cap off and open each tap on the coolant rail until all air is gone (keeping the header tank topped up).
Leave the cap off and leave the engine running, as soon as the stat opens and the coolant temp hits about 80°C check the level, top up and replace the cap.
Now leave until the fans have cycled a couple of times and then leave to cool.
Once cooled fully check level again.
All should be good to go but check after the first drive as the increase in flow when the engine speed is raised can push out more air.
I fill the system with 50:50 mix with the rad bleed open.
Once this vents coolant close it off and open the 2 coolant rail pipes. Continue to fill.
Once they vent coolant close and top the system to the top.
Now start the engine with the cap off and open each tap on the coolant rail until all air is gone (keeping the header tank topped up).
Leave the cap off and leave the engine running, as soon as the stat opens and the coolant temp hits about 80°C check the level, top up and replace the cap.
Now leave until the fans have cycled a couple of times and then leave to cool.
Once cooled fully check level again.
All should be good to go but check after the first drive as the increase in flow when the engine speed is raised can push out more air.
When my ZT-T 260 'blew' it's radiator up (literally!) I had a really good guy come out who built a new rad for me. After fitting and bleeding the system he showed me an interesting way to correctly fill the system.
Set the heater control to maximum.
Start and run the engine with the filler cap off.
Open bleed valves once of twice until no more air comes out.
Keep running the engine until stat opens.
Keep topping the header tank up as necessary.
When the engine hits max temperature (fans both on) turn off engine,
Fill header up if necessary then replace filler cap.
He said that using this method will ensure that the coolant system ends up with the correct expansion (air) volume so that a) it has the maximum possible amount of coolant and b) At maximum temperature the system will not over pressurise and dump water.
I have used this method on the 6 cars I have owned since then and I have never had any overheating problems or had any water overflow at high temperatures. When checking the levels cold against the normal 'full' marks on the header tank I got some pretty varied results!! The Cerb is usually a little lower than the normal mark.
Set the heater control to maximum.
Start and run the engine with the filler cap off.
Open bleed valves once of twice until no more air comes out.
Keep running the engine until stat opens.
Keep topping the header tank up as necessary.
When the engine hits max temperature (fans both on) turn off engine,
Fill header up if necessary then replace filler cap.
He said that using this method will ensure that the coolant system ends up with the correct expansion (air) volume so that a) it has the maximum possible amount of coolant and b) At maximum temperature the system will not over pressurise and dump water.
I have used this method on the 6 cars I have owned since then and I have never had any overheating problems or had any water overflow at high temperatures. When checking the levels cold against the normal 'full' marks on the header tank I got some pretty varied results!! The Cerb is usually a little lower than the normal mark.
PoleDriver said:
When my ZT-T 260 'blew' it's radiator up (literally!) I had a really good guy come out who built a new rad for me. After fitting and bleeding the system he showed me an interesting way to correctly fill the system.
Set the heater control to maximum.
Start and run the engine with the filler cap off.
Open bleed valves once of twice until no more air comes out.
Keep running the engine until stat opens.
Keep topping the header tank up as necessary.
When the engine hits max temperature (fans both on) turn off engine,
Fill header up if necessary then replace filler cap.
He said that using this method will ensure that the coolant system ends up with the correct expansion (air) volume so that a) it has the maximum possible amount of coolant and b) At maximum temperature the system will not over pressurise and dump water.
I have used this method on the 6 cars I have owned since then and I have never had any overheating problems or had any water overflow at high temperatures. When checking the levels cold against the normal 'full' marks on the header tank I got some pretty varied results!! The Cerb is usually a little lower than the normal mark.
And quite possibly boil your engine. You need the pressure on when the engine is at MAX temp to prevent boiling. You can end up boiling coolant inside the heads due to local hot spots.Set the heater control to maximum.
Start and run the engine with the filler cap off.
Open bleed valves once of twice until no more air comes out.
Keep running the engine until stat opens.
Keep topping the header tank up as necessary.
When the engine hits max temperature (fans both on) turn off engine,
Fill header up if necessary then replace filler cap.
He said that using this method will ensure that the coolant system ends up with the correct expansion (air) volume so that a) it has the maximum possible amount of coolant and b) At maximum temperature the system will not over pressurise and dump water.
I have used this method on the 6 cars I have owned since then and I have never had any overheating problems or had any water overflow at high temperatures. When checking the levels cold against the normal 'full' marks on the header tank I got some pretty varied results!! The Cerb is usually a little lower than the normal mark.
Hence why I suggest bleed until air is out and then refit the cap to heat up fully and cycle the fans.
The heater to max idea is from old cars due to them having coolant flow control valves that cut the flow of hot water to the cab heater. More modern engines have full flow to the cab heater at all times.
ridds said:
And quite possibly boil your engine. You need the pressure on when the engine is at MAX temp to prevent boiling. You can end up boiling coolant inside the heads due to local hot spots.
Hence why I suggest bleed until air is out and then refit the cap to heat up fully and cycle the fans.
The heater to max idea is from old cars due to them having coolant flow control valves that cut the flow of hot water to the cab heater. More modern engines have full flow to the cab heater at all times.
Hence why I suggest bleed until air is out and then refit the cap to heat up fully and cycle the fans.
The heater to max idea is from old cars due to them having coolant flow control valves that cut the flow of hot water to the cab heater. More modern engines have full flow to the cab heater at all times.
You will still get pressure! This method ensures that when the water expands with heat it doesn't go over pressure. Once cool and the cap replaced there is an air gap in the header which allows expansion of the water and increases pressure. As I said, the end result (for me) has ended up with water levels in the header tank which do not always agree with the 'Max' marks on the tank. In fact, the header for the Cerb is from another car, unless the engine runs at exactly the same temperature and has the same volume of water why would the 'Max' level mark be correct for the Cerb?I have read a few times about people topping their Cerbs up with water only to find them blowing water/steam out in traffic because they have been overfilled.
The guy who showed me this method had been building/replacing radiators for 25 years so I do trust his method.
Interested in the fact that the heater matrix is permanently connected to the system and not controlled by a valve though. I've obviously not worked on enough modern cars!
ridds said:
How do you get any pressure with the cap off?
You don't! You only leave the cap off when you fill it. Water expands as it heats up, let it get to max temp (fans on, less than 100 degrees so it won't boil). When you are happy that it is full and all air out turn off. When the engine is cool the level will have gone back down. This level will ideally be at the 'Max' mark in the header (but not always!).
Then you put the cap back!
Using this method in my Cerb I've never had a boil/leak even on a very hot summers day (remember those?) after having pushed her very hard for about an hour then getting stuck for 2 hours in an M25 traffic jam. temperature has never gone over 95 degrees!
PoleDriver said:
You don't! You only leave the cap off when you fill it.
Water expands as it heats up, let it get to max temp (fans on, less than 100 degrees so it won't boil). When you are happy that it is full and all air out turn off. When the engine is cool the level will have gone back down. This level will ideally be at the 'Max' mark in the header (but not always!).
Then you put the cap back!
Using this method in my Cerb I've never had a boil/leak even on a very hot summers day (remember those?) after having pushed her very hard for about an hour then getting stuck for 2 hours in an M25 traffic jam. temperature has never gone over 95 degrees!
So, the cap is off and the both fans are active, now if you have a std chip then you would have a 95°C threshold for the second fan. Now taking in temperature switch tolerances, heat loss from exposed pipework and inefficient coolant flow at idle d you still think that the coolant temperature on the back of the combustion chamber in the rear of the cylinder heads where flow is again poorest will not be over 100°C?Water expands as it heats up, let it get to max temp (fans on, less than 100 degrees so it won't boil). When you are happy that it is full and all air out turn off. When the engine is cool the level will have gone back down. This level will ideally be at the 'Max' mark in the header (but not always!).
Then you put the cap back!
Using this method in my Cerb I've never had a boil/leak even on a very hot summers day (remember those?) after having pushed her very hard for about an hour then getting stuck for 2 hours in an M25 traffic jam. temperature has never gone over 95 degrees!
I would seriously suggest NOT allowing both fans to activate with the header tank cap off.
ridds said:
So, the cap is off and the both fans are active, now if you have a std chip then you would have a 95°C threshold for the second fan. Now taking in temperature switch tolerances, heat loss from exposed pipework and inefficient coolant flow at idle d you still think that the coolant temperature on the back of the combustion chamber in the rear of the cylinder heads where flow is again poorest will not be over 100°C?
I would seriously suggest NOT allowing both fans to activate with the header tank cap off.
Ah! I see your point here, I have had Jules fan switch mod done to mine! I would seriously suggest NOT allowing both fans to activate with the header tank cap off.
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