Coolant bleeding process?
Discussion
Hi All
I expect this may have been done already but my 99 plate 400 seems to run real cool..
After a run up from cold for 20 mins and the fans coming on and off, the top of the rad still seems cold to cool? The temp gauge seems to run at an indicated 60 degrees tops with the fans on. The input side of the rad is hotter (passenger side) and the bottom hose (drivers side bottom) seems warm but not hot. The main coolant reservoir is half full and also seems warm at best. I have slackened off the rad bleed bolt and there is air cavity in there but can just see a small bit of water movement. I have tried topping it up but is just then fills the main reservoir? So the car runs perfectly albeit very cool and the heater does work but not hot... With a laser temp gauge it confirms the gauge reading.
So I am assuming (always dangerous) that I have a air lock somewhere so if anyone can give me the tried and tested sequence to "burp" the car it would be appreciated
Thanks in advance
Chris
I expect this may have been done already but my 99 plate 400 seems to run real cool..
After a run up from cold for 20 mins and the fans coming on and off, the top of the rad still seems cold to cool? The temp gauge seems to run at an indicated 60 degrees tops with the fans on. The input side of the rad is hotter (passenger side) and the bottom hose (drivers side bottom) seems warm but not hot. The main coolant reservoir is half full and also seems warm at best. I have slackened off the rad bleed bolt and there is air cavity in there but can just see a small bit of water movement. I have tried topping it up but is just then fills the main reservoir? So the car runs perfectly albeit very cool and the heater does work but not hot... With a laser temp gauge it confirms the gauge reading.
So I am assuming (always dangerous) that I have a air lock somewhere so if anyone can give me the tried and tested sequence to "burp" the car it would be appreciated
Thanks in advance
Chris
Okay, well bleeding is an odd process, the expansion pot sits low so filling and bleeding is best done elsewhere. I find bleeding via the swirl pot is the best option as it sits high in the system and nicely gathers any circulating air. Fill it to brimming then replace the cap and vigorously and repeatedly squeeze the hoze leading to the top of the swirl pot. Check the swirl pot level again and repeat until no more water will go in. Run the engine hot, let it cool and repeat the swirl pot filling. Ensure the expansion pot is approx 1/3 full when cold. Don't fill any higher as it needs a lot of space for expansion
On the top of the nearside cylinder head there is a pipe which has got a bolt shoved in the end with a jubilee clip to hold it in place. It sits somewhere near the throttle potentiometer, it's used to bleed air from the top of the engine. Remove it until water flows out (after releasing the pressure from the system).
FWIW this is how I fill/bleed the cooling system.
First you need a large plastic funnel ie about 30 centimeters high and 30 centrimeters diametre.
The neck of the funnel needs to be small enough to fit in the threaded hole on top of the swirl pot.
Remove the swirl pot plug a screw the funnel in place and fill the funnel so the swirl pot is full and there is head of water above it in the funnel.
Start the engine and keep topping up the funnel as air is displaced by the engine. Ensure heater controls are set to hot position.
Continue to top up the funnel, maintaining a head of water in the funnel, until no more air comes out the system and engine is at full temperature. Unscrew the funnel and quickly put the plug back in.
Whole process takes about 15 minutes and always works.
First you need a large plastic funnel ie about 30 centimeters high and 30 centrimeters diametre.
The neck of the funnel needs to be small enough to fit in the threaded hole on top of the swirl pot.
Remove the swirl pot plug a screw the funnel in place and fill the funnel so the swirl pot is full and there is head of water above it in the funnel.
Start the engine and keep topping up the funnel as air is displaced by the engine. Ensure heater controls are set to hot position.
Continue to top up the funnel, maintaining a head of water in the funnel, until no more air comes out the system and engine is at full temperature. Unscrew the funnel and quickly put the plug back in.
Whole process takes about 15 minutes and always works.
The radiator on a Chimaera is a cross flow design, to check for air locks in the rad itself put your hand over each fan when they chime in to feel the fan exhaust air temp. The cross flow path of the coolant within the rad moves from the near side to the off side, engine heated coolant enters from the cylinder heads to the the rad tank on the near side, and exits cooled at the bottom hose on the off side rad tank.
Its quite common when you feel the fan exhaust air temp on the off side fan is cooler than the air exhausted by near side fan, this indicates there is poor coolant flow across the rad and is likely a sign of an air lock, this is why the rad bleed screw is on the top of the off side rad tank. Open this screw and fill the rad from here with a small funnel, increase the engine speed, burp and refill. Keep doing this while squeezing the top hose on the near side of the rad, keep filling and burping until the air exhausted by the off side rad fan is more or less as hot as the air being exhausted by the near side fan, refit the bleed screw as your cross flow rad is now working correctly, if not return to the primary bleeding process at the swirl pot, then go back to bleeding the rad.
Keep in mind even if everything with your cooling system is working correctly in the cooler months the aluminum RV8 engine block is a very effective heat sink by itself, super cooled winter air rushing over the engine block will lower engine temps below that of your thermostat value. Also consider all water cooled engines are actually oil and water cooled, a good percentage of the engine's heat is actually transferred to the oil and a sump sat in winter airflow will lose heat from the oil far more effectively than in the summer months.
Fitting an 88 degree thermostat is recommended as this will help the engine get up to it's correct operating temperature faster, however even with an 88 degree thermostat and the correct TT6811-03 temp sender fitted what you'll find is a Chimaera will still overcool in the winter months due heat being lost through the aluminum block and through the sump, both of which are sat in super cooled airflow. I run an 88 degree thermostat and the correct TT6811-03 temp sender but still see true coolant temps on my Canems software fall to a low of 77 degrees at speed on a winters day.
Basically the engine at speed in cold weather runs 10 degrees cooler than is ideal, the simplest way to solve this is with a rad blind which need be nothing more sophisticated than a piece of cardboard over a portion of the off side end of the rad. You install the cardboard on the offside as a Chimaera has a cross flow radiator, this cross flow design cools the coolant as it passes from the near side where it enters from the heads across the rad to the off side where it exits at the bottom hose.
By restricting airflow over the coldest off side half of the rad you can most effectively raise the temp of the coolant that is returned to the engine block, and coolant temp across the entire rad will be more consistent. Be careful not to over restrict air flow, the over cooling issue only occurs at speed so the amount you cover the off side of the rad must not be too great or you run the risk of overheating in town or when stuck in traffic. Its a balance between the two which will likely take some experimentation to get right, but at least with the correct TT6811-03 temp sender fitted you can keep an accurate eye on whats going on which is something you cant say if you've still got the TVR sender fitted in the stupid blind spur adapter they used.
As the weather improves you will want to lose your ghetto rad blind altogether but the 88 degree thermostat should remain as this is the correct value for the engine despite what anyone else says, if your cooling system is in good health the fans will chime in at 92c and lower your coolant to 85c before the cycle repeats itself, with a lower value thermostat you will still see a peak of 92c because peak coolant temp is governed by the coolant system capacity and fan on temp not the thermostat, assuming you are not stupid enough to fit a thermostat of of a higher value that the correct 88c that is.
1. Fit a cardboard rad blind covering a portion of the off side of the rad
2. Fit the correct 88c thermostat
3. Fit the correctly matched TT6811-03 temp sender in the inlet manifold coolant flow to monitor true coolant temps
4. Make sure your coolant system is is good health, correctly bled and filled with a 50/50 mix of quality anitifreeze
If you complete the above for steps you'll find you can safely achieve 83c at speed on a winters day without risking overheating in traffic, you will find the car is far more pleasant to use in the winter as the heater will perform way better.
Its quite common when you feel the fan exhaust air temp on the off side fan is cooler than the air exhausted by near side fan, this indicates there is poor coolant flow across the rad and is likely a sign of an air lock, this is why the rad bleed screw is on the top of the off side rad tank. Open this screw and fill the rad from here with a small funnel, increase the engine speed, burp and refill. Keep doing this while squeezing the top hose on the near side of the rad, keep filling and burping until the air exhausted by the off side rad fan is more or less as hot as the air being exhausted by the near side fan, refit the bleed screw as your cross flow rad is now working correctly, if not return to the primary bleeding process at the swirl pot, then go back to bleeding the rad.
Keep in mind even if everything with your cooling system is working correctly in the cooler months the aluminum RV8 engine block is a very effective heat sink by itself, super cooled winter air rushing over the engine block will lower engine temps below that of your thermostat value. Also consider all water cooled engines are actually oil and water cooled, a good percentage of the engine's heat is actually transferred to the oil and a sump sat in winter airflow will lose heat from the oil far more effectively than in the summer months.
Fitting an 88 degree thermostat is recommended as this will help the engine get up to it's correct operating temperature faster, however even with an 88 degree thermostat and the correct TT6811-03 temp sender fitted what you'll find is a Chimaera will still overcool in the winter months due heat being lost through the aluminum block and through the sump, both of which are sat in super cooled airflow. I run an 88 degree thermostat and the correct TT6811-03 temp sender but still see true coolant temps on my Canems software fall to a low of 77 degrees at speed on a winters day.
Basically the engine at speed in cold weather runs 10 degrees cooler than is ideal, the simplest way to solve this is with a rad blind which need be nothing more sophisticated than a piece of cardboard over a portion of the off side end of the rad. You install the cardboard on the offside as a Chimaera has a cross flow radiator, this cross flow design cools the coolant as it passes from the near side where it enters from the heads across the rad to the off side where it exits at the bottom hose.
By restricting airflow over the coldest off side half of the rad you can most effectively raise the temp of the coolant that is returned to the engine block, and coolant temp across the entire rad will be more consistent. Be careful not to over restrict air flow, the over cooling issue only occurs at speed so the amount you cover the off side of the rad must not be too great or you run the risk of overheating in town or when stuck in traffic. Its a balance between the two which will likely take some experimentation to get right, but at least with the correct TT6811-03 temp sender fitted you can keep an accurate eye on whats going on which is something you cant say if you've still got the TVR sender fitted in the stupid blind spur adapter they used.
As the weather improves you will want to lose your ghetto rad blind altogether but the 88 degree thermostat should remain as this is the correct value for the engine despite what anyone else says, if your cooling system is in good health the fans will chime in at 92c and lower your coolant to 85c before the cycle repeats itself, with a lower value thermostat you will still see a peak of 92c because peak coolant temp is governed by the coolant system capacity and fan on temp not the thermostat, assuming you are not stupid enough to fit a thermostat of of a higher value that the correct 88c that is.
1. Fit a cardboard rad blind covering a portion of the off side of the rad
2. Fit the correct 88c thermostat
3. Fit the correctly matched TT6811-03 temp sender in the inlet manifold coolant flow to monitor true coolant temps
4. Make sure your coolant system is is good health, correctly bled and filled with a 50/50 mix of quality anitifreeze
If you complete the above for steps you'll find you can safely achieve 83c at speed on a winters day without risking overheating in traffic, you will find the car is far more pleasant to use in the winter as the heater will perform way better.
checking that its properly bled is always good practice, but consider that you'r thermostat may be stuck and causing a false reading, and consider that the temp sender/gauge are getting old and likely starting to act up.
for reassurance you might consider buying a 'standalone' gauge and sensor such as those found here;
https://www.vdo-gauges.com/instruments-displays-an...
if both gauges agree with each other you're golden, but if theyre differnet you will need to do some more digging.
for reassurance you might consider buying a 'standalone' gauge and sensor such as those found here;
https://www.vdo-gauges.com/instruments-displays-an...
if both gauges agree with each other you're golden, but if theyre differnet you will need to do some more digging.
Olas said:
checking that its properly bled is always good practice, but consider that you'r thermostat may be stuck and causing a false reading, and consider that the temp sender/gauge are getting old and likely starting to act up.
for reassurance you might consider buying a 'standalone' gauge and sensor such as those found here;
https://www.vdo-gauges.com/instruments-displays-an...
if both gauges agree with each other you're golden, but if theyre differnet you will need to do some more digging.
The TT6811-03 temp sender is proven to be perfectly matched to the TVR Caerbont gauge, Caerbont instruments designed it that way.for reassurance you might consider buying a 'standalone' gauge and sensor such as those found here;
https://www.vdo-gauges.com/instruments-displays-an...
if both gauges agree with each other you're golden, but if theyre differnet you will need to do some more digging.
https://www.pistonheads.com/gassing/topic.asp?h=0&...
Thermostats rarely fail but people do fit lower value ones in the misguided belief they will save the car from overheating in the summer, this does not and cannot work because peak coolant temp at idle when overheating may occur is set by the coolant system capacity and air flow not the thermostat. The Chimaera is well known to overcool in the winter months for the reasons I've already covered, so once bled correctly whats seen on the gauge is what the coolant temp really is in the inlet manifold if a TT6811-03 temp sender is used and will be close to what the water jacket temp will be around the combustion chamber.
Winter over cooling is a well know age old trait of our cars, avoid low value thermostats for a start as the engine will take for ever to warm up, with the correct 88c thermostat in place things can be improved a little further with a small portion of the O/S side of the rad blocked off, but only in the winter months!
Thanks again for the advice guys ..
As mentioned I have done the coolant sensor upgrade / move and the rad temp (hot side) by laser thermometer seems to be spot on.
After 15 / 20 mins of running and the fans coming on and off the temp shown on the dial is about 65 degrees
Did the funnel technique with heater blower full on and it took about a coffee cup of coolant and one / two small bubbles but nothing else so all sealed up and re-checked the rad top bleed screw and coolant squirts out with no air.
The main filler tank (blue top) is about half full and seems only warm to touch.
The car runs at this temp at the moment with no overheating etc. The ambient temp here is about 8 degrees so possibly as mentioned the car is just over cooling at this time of year?
I am tempted to leave it as is and see how it goes when the weather warms up. I will try RG on it at the weekend.
As mentioned I have done the coolant sensor upgrade / move and the rad temp (hot side) by laser thermometer seems to be spot on.
After 15 / 20 mins of running and the fans coming on and off the temp shown on the dial is about 65 degrees
Did the funnel technique with heater blower full on and it took about a coffee cup of coolant and one / two small bubbles but nothing else so all sealed up and re-checked the rad top bleed screw and coolant squirts out with no air.
The main filler tank (blue top) is about half full and seems only warm to touch.
The car runs at this temp at the moment with no overheating etc. The ambient temp here is about 8 degrees so possibly as mentioned the car is just over cooling at this time of year?
I am tempted to leave it as is and see how it goes when the weather warms up. I will try RG on it at the weekend.
this the swirl pot below is the one you always fill cooling system with 
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