By Jeff Barker
With summer heat finally settling in, you’ve probably put your winter trucking gear away and are looking forward to being productive during the normally busier time of the year. But have you taken care of everything?
Of course, the summer heat will often bring out the weak points in a truck’s engine cooling system, which can then lead to uncomfortable circumstances. As with just about anything else on your truck, a little bit of maintenance will go a long way toward avoiding an A/C system breakdown.
Coolant hoses and clamps
If your truck’s cooling system has standard rubber hoses, they should be replaced every four years. Silicone hoses, normally identified by being blue or green in color, can last eight to 10 years, unless they’re in an extreme high-heat area, such as next to the engine block or a hot exhaust component.
Hoses next to the engine block are often the most overlooked. Many people don’t even know about them until they fail and begin spewing out antifreeze. They can be hard to find because manufacturers often paint over them after engines are built but before they are installed.
If you look hard enough for hose clamps on engine-mounted components such as the air compressor, oil cooler, water pump, etc., you can find those hoses. They should be replaced every four years, along with the heater hoses and rubber coupling sleeves in the plumbing to and from the radiator. As always, never reuse old hose clamps if new ones are readily available.
Make sure the hoses are secure and not rubbing on anything. If needed, black cable ties will work to secure them. If you have hoses that are close to something but there is no way to tie them away, grab an old section of heater hose to use as a barrier. Carefully cut a slit down the desired length of it, place it over the area of the new hose where it could rub, and use some cable ties to hold the barrier in place.
Fan clutch and belt
Fan clutches and the hubs they’re mounted to almost never get any attention until they fail. If one comes apart because of a bearing failure, you’ll be stuck and waiting for a tow truck. That would be bad enough, but if the fan clutch comes off the hub, your radiator core can be trashed and need to be replaced.
Other failures associated with fan clutches include the idler bearing inside them and the seals around the piston, which can cause air to leak. The escaping air is easier to hear with the engine off.
The linings on the fan clutch wear out over time and should be replaced. You can see the linings by looking at the fan clutch from the side. Turn your truck’s ignition key on so the fan turns freely and look for the gap between the linings. By most standards, if the gap is more than one-eighth of an inch, that means the linings are worn.
It’s a good practice to replace your truck engine’s belts once a year, regardless of the mileage. While you have the fan belt off, grab the fan clutch and turn it. If it binds up and/or has any up and down movement, the fan hub bearings are toast. You should also check the idler pulley bearing on the belt tensioner using the same method.
Rebuilding a fan clutch and hub yourself is not hard to do, especially if you have a good bench vise and are willing to read and follow the directions in the rebuild kit. It’s more convenient and less expensive to handle this at home instead of going through the hassle of trying to locate a rebuilt unit on the road.
If you see a damaged fan blade, replace the fan. If the fan blade assembly is out of balance, it eventually will destroy the bearings on the fan hub.
Radiator and fan shroud
Two important parts of an efficient cooling system are the radiator and fan shroud. This is especially true on later model trucks equipped with EGR engines, which place even higher demands on cooling systems.
Check your truck’s fan shroud on occasion. It needs to be in place and intact to help the fan draw air through the radiator.
Radiator fins should be cleaned once a year to remove caked-in bugs and other debris that can cause blockage and hurt cooling efficiency. Here’s a do-it-yourself procedure that works quite well:
- Get a couple of cans of radiator fin and A/C coil cleaner. You can find it at just about any parts store or RV supply shop. I’ve even used Easy-Off oven cleaner for this.
- Park the tractor on a hard surface where water runoff won’t be a problem. Be sure to take the keys out of the ignition.
- Remove the grille and put it in a safe place – not on the ground where your kids can run over it with a bike or where your dog can lift a leg to let you know what he thinks of your truck.
- Cover any surfaces you want to protect – especially your hood, fenders, and bumper – with a tarp. That cleaner is potent stuff and can harm paint and chrome.
- With the hood up and the engine off, spray one entire can of cleaner onto the back side of the radiator, distributing it evenly.
- Lower the hood and spray the other can onto the front of the radiator, A/C condenser, transmission cooler, if applicable, and the charge-air cooler.
- Wait about 20 minutes – or however long the instructions on the can tell you.
- Using a garden hose with a low-pressure spray nozzle (to avoid bending and damaging the fins), thoroughly rinse the entire radiator, condenser, and charge-air cooler. Spray off your engine to avoid getting the oven cleaner into your electrical system connections. Note how much crud is on the ground under the freshly cleaned radiator.
- Once your radiator is dry, remove the tarps and put your grille back on. Use a drop of Loctite (or other thread adhesive) on the threads of every bolt and screw so they stay in place.
Radiators typically last about 700,000 miles before vibration and road shock eventually cause their cores to crack at the header – where the tubes meet the end plates that the tanks mount to. Then they begin to leak profusely, often enough to trigger the low coolant warning and put your truck on the side of the road.
When that happens, it’s best to have the entire core replaced instead of attempting to repair it. If your radiator has plastic tanks, you will be better off getting a complete new radiator with metal tanks from a reputable radiator shop. Never reuse plastic radiator tanks, because they dry rot and tend to crack over time.
Antifreeze, water and additives
Antifreeze in your cooling system has more than one job to do: It lubricates your engine’s water pump seals, raises the boiling point of the water in the coolant, and lowers the freeze point to protect your engine from freeze damage in the winter.
With different types of antifreeze on the market now, do yourself a favor and avoid switching from what has already been used in your cooling system.
As for water, your engine’s cooling system will benefit from using purified water instead of tap water. In many areas of the country, the tap water contains too much lime and calcium – neither of which are good for your cooling system.
Most over-the-road trucks should have a 50/50 mix of antifreeze and water in their cooling systems. If you operate your truck in extremely cold climates most of the time, you can lower the freeze point of the coolant a bit more by mixing your antifreeze and water at a 60/40 rate.
Supplemental coolant additives are an absolute must to prevent cylinder liner pitting, which could lead to serious engine damage. Coolant test strips are available for the purpose of testing the SCA level in your coolant. You need to check and adjust it as necessary at every scheduled preventive maintenance or more often if your cooling system needs to be refilled on occasion because of a slow leak.
Some coolant filters have what are known as “timed release” SCA additives in them. The coolant should still be tested at every PM to make sure the SCA additives are at the right level.
While we’re on the subject of coolant filters, check for rust on their metal cases. The cases can rust through and eventually leak.
Last, but certainly not least, is the water pump. It’s the heart of your truck’s cooling system. Check it regularly. If it starts to leak, antifreeze can be seen around the weep hole that’s usually visible near the bottom of the water pump. This indicator is a good warning to let you know when your water pump is headed south.
If you plan to keep your truck for a while, do yourself a favor and get a new water pump instead of a remanufactured one. LL
Editor’s note: This article is for information purposes only. If you’re not sure about performing the work yourself, it’s advisable to seek the help of a competent professional.
Jeff Barker is an OOIDA member and a former certified diesel mechanic. He can be reached at firstname.lastname@example.org.