Motorsport Plumbing Systems: Bleeding The Coolant System
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Bleeding The Coolant System
07.29
| 00:00 | Bleeding a vehicle's coolant system involves removing any air from the system and ensuring that it's full of coolant. |
| 00:07 | This is required after any work on the system that results in loss of fluid or after the initial installation. |
| 00:14 | The coolant system needs to be full of coolant and have no air bubbles for multiple reasons. |
| 00:19 | First, as we know, the coolant serves the purpose of transferring heat from our engine and the more coolant we have in the system, the more thermal capacity we have to aid in this heat transfer process. |
| 00:31 | So, naturally, we want to make sure it's full. |
| 00:34 | Past this, if we have minimal coolant in the system, the water pump simply won't be able to pump it effectively. |
| 00:41 | Regardless, the risk is still the same. |
| 00:43 | Our coolant system won't be able to serve its purpose, leading to potential overheating of our engine, which can result in expensive and irreversible damage. |
| 00:52 | How difficult the system is to bleed comes down to its design and routing. |
| 00:57 | Put simply, any local high points can create air pockets that can be difficult to clear. |
| 01:03 | So, this is naturally something we want to avoid when designing and building the system. |
| 01:08 | Essentially, we want the fill point to be the highest point so air can pass through the plumbing and out this point as we fill the coolant. |
| 01:16 | Sometimes jacking up the front of the vehicle or parking it on a slope can help. |
| 01:21 | Assuming we have a front mounted radiator that has a cap as the fill point, which is by far the most common arrangement. |
| 01:28 | Another option here is to use a funnel designed specifically to seal on the radiator port and further raise the fill point. |
| 01:35 | These also use a valve to block off the port when it comes time for removal to stop spillage. |
| 01:41 | Some vehicles will also have bleed points, which are small valves to release air pockets at high points if there is no alternative during the design phase. |
| 01:50 | There are actually two basic methods of bleeding the coolant from the system. |
| 01:54 | So, we'll cover both starting with the simpler manual method. |
| 01:59 | With the fill cap open, we start by filling the system to its maximum capacity, including the expansion tank. |
| 02:06 | If the radiator plumbing uses rubber hoses we can sometimes squeeze them to provide a pumping effect and move fluid through the system. |
| 02:14 | This can also provide indication of how much fluid is in the hose by how hard it is to squeeze. |
| 02:21 | An empty hose will be fairly easy to compress but a full hose will feel quite firm. |
| 02:26 | With the radiator full, we can start the engine, which will engage the water pump and start moving the fluid through the system. |
| 02:33 | We need to get it up to temperature so the thermostat can open and the coolant can flow through the entire system. |
| 02:40 | This could be a risky process and it's important to watch the temperature gauge, assuming it's reliable and ensure we never get the engine too hot. |
| 02:49 | The other important thing to remember is that the interior heater, if it's still in place, needs to be switched on to its maximum hot temperature setting. |
| 02:58 | This system uses heated coolant from the engine and so is part of the capacity we want to fill with fluid. |
| 03:04 | We also need to open any bleed points if present until the coolant comes out of them. |
| 03:10 | Sometimes, we can actually attach a small hose to these fittings to avoid spillage. |
| 03:14 | Some light revving can also help move coolant and dislodge stubborn air pockets. |
| 03:19 | As the air evacuates from the system, we need to continue filling the coolant to maintain the maximum level. |
| 03:26 | Naturally, we should be careful when doing this job as we're working with a hot fluid around hot components and potentially running cooling fans. |
| 03:34 | After we're confident the coolant system is full, we can fit the radiator or fill cap and take the vehicle for a drive while monitoring the coolant temperature. |
| 03:43 | When we return, as you're probably aware, we don't want to open the radiator cap while it's still hot. |
| 03:49 | Once the system has cooled completely, if the coolant level has gone down, we need to top it up again until full. |
| 03:56 | The alternative method is to use a vacuum bleeding kit, and although this does come at an extra expense that might not always be required, it does guarantee a successful bleed. |
| 04:07 | And for some coolant systems with local high points, this is almost a necessity. |
| 04:12 | This works by connecting to the coolant fill point and forming a seal. |
| 04:17 | Compressed air can be used to blow through the venturi port with the valve open to create a vacuum in the coolant system. |
| 04:24 | Rubber hoses will often collapse with this, but that shouldn't be an issue unless the hoses have perished and cracked, at which point they should probably be replaced anyway. |
| 04:34 | Again we should make sure the heater is on if fitted so the system is open and can be filled with coolant. |
| 04:40 | If there is coolant in the system already, it's best to attach a hose to the other end of the venturi and have this in a bucket outside the vehicle for any coolant drawn from the system. |
| 04:50 | The vacuum gauge allows us to see how much vacuum we're pulling and it's important to follow the instructions of the kit here. |
| 04:58 | But usually we'd aim for between negative 50 to negative 60 centimetres, or negative 20 to negative 24 inches of mercury of vacuum, which will be clearly shown on the gauge. |
| 05:09 | Once this has been reached, we close the venturi valve and stop the compressed air. |
| 05:14 | Keeping an eye on the gauge, our system should hold vacuum, indicating it's tight with no leaks. |
| 05:20 | This is an important step and it's worth monitoring this over a period of 5 to 10 minutes to ensure the system is holding vacuum before commencing to fill the system with coolant. |
| 05:30 | With a vacuum in place, we can use this to draw in coolant and completely fill the system. |
| 05:36 | This is where the other port on the device is used. |
| 05:39 | We attached one end of the hose here with the other end completely submerged in coolant. |
| 05:45 | If we're using a concentrate, it's best to have this pre mixed in a clean container. |
| 05:50 | It's important that the end of the hose remains completely submerged so we don't draw air into the system. |
| 05:56 | And in the same thinking, we need to clear any air from the hose first so this doesn't enter the system. |
| 06:02 | The best way to do this is to use the venturi system, as we did before but with the coolant valve open until the coolant flows up to the top of the hose where we can then close the venturi valve and disconnect the compressed air. |
| 06:15 | We can now open the coolant valve again and it'll be drawn into the system by the vacuum. |
| 06:20 | The gauge will show the vacuum gradually reducing until the plumbing is completely full of coolant. |
| 06:26 | If we're running out of coolant before the system is full, we need to close the valve and top this up so we don't run dry and draw in air. |
| 06:35 | When the system is full and the vacuum is gone, the coolant will stop flowing, at which point we can close the valve and disconnect the device. |
| 06:43 | It's normal to have to top up a small amount of coolant after this, but otherwise the system should be fully bled. |
| 06:50 | So, we can go for a test drive, keeping an eye on the temperature gauge, then finally once cooled and depressurised, we can double check the coolant level for the final time. |
| 07:00 | Let's summarise what we've covered in this module before moving on. |
| 07:04 | Bleeding the coolant system is necessary to ensure the system performs as intended and cools our engine. |
| 07:10 | This can be done by filling the system and running the engine with the heater on. |
| 07:14 | The main challenge is to remove air if there are high points above the fill point. |
| 07:19 | Vacuum bleeder kits are useful here, this creates a vacuum in the system to draw in coolant and completely fill the plumbing. |
