Skip to content

6.7 Cummins Heater Hose Diagram

Hoses degrade from the inside out, which makes detecting their decay difficult. Hoses that continue to degrade develop tiny cracks and pinholes which can lead to ruptures from the pressure, contractions, and exposure to heat.Heater hoses are smaller hoses that are attached to the heater core, which is located under the dashboard, to supply warmth to passengers in the cabin.

What size heater hose do I need?
The most common sizes of heater hose are 5/8″ and 3/4″. Inside a heater hose you can see the edges of the cords. Note the thin wall and sparse cord, this is low-pressure stuff. Radiator hoses are also lined with cords, but they are typically molded to shape to help prevent kinking and for better flow.
The upper radiator hose is connected to the thermostat housing and to the radiator. From the bottom of the radiator, is the lower radiator hose that is directed to the water pump. Powered by the vehicle’s water pump, the engine coolant loses its heat after passing through the radiator. Both the upper and lower radiator hoses are the largest hoses in the cooling system connected to the engine.An overflow hose connects to the radiator below the cap and the reservoir tank to store overflow of coolant. As pressures in the cooling system increase due to coolant temperatures, a valve on the radiator cap permits coolant back into the reservoir to help ease the build-up of pressure and prevent coolant loss.

How do I identify an inlet and outlet?
The easiest way to do this is to look at the direction of the valve. If the valve is pointing towards the radiator, then it is the inlet valve. This means that hot water is entering the radiator through this valve. On the other hand, if the valve is pointing away from the radiator, then it is the outlet valve.
The vehicle’s thermostat remains closed upon start up until coolant reaches a designated temperature. To prevent coolant from traveling to the radiator for cooling, the fluid is directed back to the engine block, through an externally-mounted bypass hose.Excessive ambient temperatures, engine heat, and rubber materials are all factors that lead to hoses drying out and hardening. Additionally, certain acids in the cooling system can cause deterioration and eat away at the rubber, compromising the integrity of the hoses. Avoiding hose replacement can cause a variety of concerns such as leaking coolant, making the engine run hotter, and lead to overheating.

The vehicle’s hoses are the cooling system’s most vulnerable structural component made of flexible rubber composites that handle vibrations from the engine. Hoses are designed to withstand coolant under intense pressure, extreme temperatures, oils, dirt, and sludge.Radiator hose replacement costs and heater hose replacement costs can range between $150 and $450 with heater hoses on the lower side while coolant hoses are a bit more costly. Though the cost of replacement may seem surprising, replacing the hoses versus replacing an engine from excessive overheating, is considerably less.

If you’ve ever popped the hood of your car, you’ve probably noticed a maze of hoses that wind around the engine. While they don’t look like much, they are like the underground subway of the engine.
It’s the only means of transportation throughout the engine used to transfer fluid to keep the engine cool and some, to warm the air, to keep passengers warm in the winter. Over time car radiator hoses and other vital hoses, which are mostly made of rubber, begin to break down from dry air, heat, and use.

Belt and hose failures can stop you in your tracks. These failures often result in overheating or the loss of power steering or charging system. If a hose begins to leak coolant or the belt turning the water pump detaches, the cooling system will fail and cause overheating. Engine overheating can cause serious internal damages that may lead to costly repairs. What can you do to prevent failure in your vehicle’s hoses:
Unfortunately, vehicle manufacturers have not outlined a certain time for when these crucial components should be replaced. That’s why it’s so important to have these hoses inspected often and replaced at the slightest sign of wear, before it’s too late.

With the dry, hot temperature synonymous with Arizona, consider replacing your hoses and hose clamps every 4 years or every 50,000 miles not to exceed 75,000 miles. Clamps keep the engine and radiator hoses in place and can weaken from constant tension over time.Each time your vehicle visits a Sun Devil Auto, such as with an oil change, we perform a multi point inspection that includes a check of the belts and cooling, radiator, and heater hoses in your car. When it’s time to replace your vehicle’s hoses, you can trust the experienced Technicians at Sun Devil Auto to replace them properly and in most cases, the same day!

Does it matter which heater hose goes where?
Comes back out and then leads to the outlet. The reason. Why they have the inlet on the bottom. And the outlet on the top is.
Upgrade your upper heater hose in your 1998.5-2023 5.9L or 6.7L Ram Cummins with this black braided hose from Full Send Diesel. This hose is made from the highest quality An fittings and hose. Backed … read more Upgrade your upper heater hose in your 1998.5-2023 5.9L or 6.7L Ram Cummins with this black braided hose from Full Send Diesel. This hose is made from the highest quality An fittings and hose. Backed by a lifetime workmanship warranty, Full Send Diesel guarantees you the perfect product. This hose replaces your upper factory heater hose with a black nylon steel braided hose. This includes all the necassary fittings and hose to get the job done. Still not sure which is which? Just run the engine for a bit and—carefully—touch each hose. The hotter one will be the inlet, and the cooler one is the outlet.

How do I know which heater core hose is inlet and outlet?
Just run the engine for a bit and—carefully—touch each hose. The hotter one will be the inlet, and the cooler one is the outlet. And if there’s still some confusion, the inlet hose will be coming from the engine and the outlet will be retuning to the water pump or radiator.
Once it’s all connected, you simply begin flushing the water through the heater core, taking note of any grit or debris that comes out the other side. Again, don’t apply too much water pressure and keep a keen eye on the dump hose, once the water that’s coming out of the heater core outlet is clear, then your work is over.In a nutshell, the heater core absorbs the heat from the engine coolant. Then, air is pushed through the heater core via your HVAC blower motor, heating it up on its way to the passenger cabin.Heater cores and radiators are both referred to as heat exchangers, which is a fancy way of saying they take heat from a source (the engine) and transfer it to a fluid—in this case, ambient air (and yes, air is a fluid).

While some older cars and trucks have a handy access panel in the engine bay, many newer vehicles do not, which means you’ll probably have to do some interior disassembly to do a heater core swap or repair.

Is inlet radiator hose upper or lower?
Radiator Hose. Most vehicle cooling systems are comprised of four main hoses. The upper radiator hose is connected to the thermostat housing and to the radiator. From the bottom of the radiator, is the lower radiator hose that is directed to the water pump.
For starters, since they’re often subjected to vibration, heat cycles, and potential chemical coolant contamination, heater cores can develop leaks. Sometimes these leaks are from a crack at a brazed copper joint, while other times they’re just tiny pinhole leaks from pitting and age. Whatever the cause, heater core leaks usually manifest in the smell of coolant inside the vehicle, soggy, stained footwell carpet, or just a chilly interior.

What size is the heater hose on a Cummins?
5/8″ 5/8″ diameter.
Thanks to their location inside the passenger area, heater cores can be pretty difficult to get at—we’re talking potential remove-the-entire-dash level difficulty here.And if there’s still some confusion, the inlet hose will be coming from the engine and the outlet will be retuning to the water pump or radiator. Just remember the fundamental principle that your heater core inlet is typically going to receive coolant at or near its hottest point, which usually means directly from the engine. And the outlet is going to usually feed the newly-chilled coolant back to the water pump or radiator so it can start a new journey through the motor.

A heater core works in the same way as your engine’s radiator—only with a different goal. A radiator is there to keep your engine operating at a consistent temperature and most of its job involves cooling the engine by extracting heat to dissipate in the ambient air.
Put simply, a heater core is part of your automobile’s climate control system and helps fill your car, truck, or SUV’s passenger compartment with warm, comfortable air. In other words, a heater core lets you stay toasty as you drive, regardless of the temperature outside.

The difficulty of a heater core swap or repair is entirely dependent on your vehicle. And that’s particularly true in modern cars, where you’ll often have to contend with things like sound/heat insulation, airbags, and more complex infotainment and HVAC system components.
A while back, we sat down with Rick Love, President of Vintage Air, for a 30 minute chat all about vehicle climate control systems. Though the talk centered primarily on air conditioning, we covered some general topics too, including installs/retrofits and common HVAC diagnostics—you can hear it all in the podcast episode below:If the air is getting warm but your fan speed control settings aren’t working properly (or if your fan isn’t working at all), then you may have a bad blower motor resistor. You can read about those here: What is a Blower Motor Resistor? And How Can You Tell if Yours is Bad?Paul is the editor of OnAllCylinders. When he’s not writing, you’ll probably find him fixing oil leaks in a Jeep CJ-5 or roof leaks in 1972 Corvette ragtop. Thanks to a penchant for vintage Honda motorcycles, he spends the rest of his time fiddling with carburetors and cleaning chain lube off his left pant leg. Remember when we said there’s a distinction between the heater core inlet and outlet hose? If you’re doing any heater core repair that requires you to remove those hoses, then you want to make sure you connect them back the same way. If you don’t, you could end up restricting the flow of coolant through the heater core and ultimately the entire engine cooling system—which, spoiler alert, isn’t ideal. You can usually spot yours by looking for those two heater hoses that route into the firewall of your engine bay—those are the aforementioned heater core inlet/outlet lines.Several companies make cooling system flush kits and solutions that can further help dissolve and break up deposits that can clog up a heater core as well.

Which hose is the heater inlet hose?
System in this step we’re going to talk about the proper. Service procedure for figuring out which heater hose is your inlet hose. As you can see on my ford explorer. I have two heater hoses.
Once you actually get to the old heater core module, it’s usually a pretty straightforward swap-in/swap-out affair. Then, of course, you have to put everything back—so we wouldn’t make any extravagant dinner plans when its time to do the job.In the name of brevity, flushing a heater core typically involves removing the two inlet/outlet hoses on the vehicle’s firewall, right at the heater core hose barbs, and replacing them with two temporary (and preferably clear) hose sections. You’ll flush your water source into the inlet port, and then attach a hose to the outlet port and feed it down into a catch bucket.

Is heater hose measured by ID or OD?
Hoses are always measured by the I.D (inside diameter or bore). This is the important measurement. The outside diameter may sometimes be quoted in a technical drawing or such like, but this is not as important.
If you think the inside of your heater core is clogged up, then there’s a chance you may be able to flush it out and unclog it. Though this process doesn’t guarantee success, it’s often worth a shot before going to the hassle or expense of a replacement heater core swap.If your blower motor is sucking in crud and debris, there’s a good chance it’ll wind up crammed in the fins of your heater core (something that’s especially true on older cars without a cabin air filter). So if you notice a lack of airflow coming from your vents, first check your cabin air filter, then see if you can get a look at your heater core—though that may take some specialty tools like an inspection mirror or a borescope.

A heater core extracts heat from your engine too, only the heat it extracts is used by your vehicle’s climate control system to warm the air in the passenger cabin.

We’ll talk about the distinction between the inlet and outlet hoses in a moment, but for now, remember that in an ICE application, a heater core shares its coolant with the rest of your engine’s cooling system. The coolant enters the heater core, passes through the fins, on its way back into the engine cooling system, hence the two ports.
If your vents are still moving plenty of air, but it’s just not getting warmer, you may have a heater core that’s clogged internally. In these cases, it means that deposits and corrosion are preventing the hot engine coolant from making its way through the heater core fins. The air from the blower motor is moving just fine—it’s just not getting hot because the heater core is still cool.

While all cars, trucks, and SUVs differ, in our experience, the heater core will be located inside the passenger cabin. And for a domestic left-hand drive vehicle in the United States, especially older models, there’s a good chance that the heater core will be located on the passenger side of the vehicle.

To begin with, there’s a good chance that the two hoses will be different sizes. Generally speaking, the inlet hose will be a slightly smaller diameter than the outlet hose. (Sometimes you’ll get lucky and the hose barbs or bulkhead will be labeled inlet/outlet, but don’t count on it.)
So, how can you tell if you need a new heater core? Well, there are a handful of signs that you need a replacement heater core—here are some good places to start:So yeah, it’s vital that your car or truck’s heater core is in good, working order to keep your passenger compartment cozy and your windows fog-free. To help yours stay that way, let’s dive into a little automotive heater core 101.

For an internal combustion engine (ICE), your heater core is fed with engine coolant. That means it’s plumbed into your engine and requires specialty heater hoses too. (That’s also the reason that your car or truck will take a while to heat up inside after its initial startup, as the heater core requires hot engine coolant to produce heat.)When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

Contact Us – Manage Preferences – Archive – Advertising – Cookie Policy – Privacy Statement – Terms of Service – Do Not Sell or Share My Personal Information –
Tubes are always measured by the O.D (outside diameter). This is the important measurement. The inside diameter might be quoted on a technical drawing etc but this is not as crucial. Tubes are measured by the O.D because they fit inside a hose.This tube above, as you can see, measures 32.18mm, so this is a 32mm outside diameter tube. All our tubes are listed with the outside diameter measurement.By ‘hoses’ we mean silicone or rubber hoses used for coolant, air, fuel, oil etc. By ‘tubes’ we mean tubes made from aluminium, mild steel, stainless steel etc to join the hoses together.Hoses are always measured by the I.D (inside diameter or bore). This is the important measurement. The outside diameter may sometimes be quoted in a technical drawing or such like, but this is not as important. Hoses are measured by the I.D because they fit over a metal/solid tube.A common question when it comes to measuring hoses and tubes is what to measure? Do we measure the O.D (outside diameter) or the I.D (inside diameter or bore)?Sometimes on hose joiners or aluminium tubes, like the one shown below, there will be a bead at the end to prevent the hose slipping off. This bead will of course measure a larger diameter than the main part of the tube itself. This is not important and does not need to be measured. When measuring a tube, always take the measurment of the predominent length of the tube – not the bead.

Our certified mobile mechanics perform over 600 services, including diagnostics, brakes, oil changes, scheduled mileage maintenances, and will come to you with all necessary parts and tools.
Your radiator is made of both metal and plastic. Metal fins allow the heat absorbed by the coolant to radiate outward, where it is wicked away by moving air. Air flows over the radiator from two sources – the cooling fan (or fans) blow air over the radiator when it reaches a certain temperature. Air also flows over the radiator when you’re traveling down the road.