The Volvo Parts, Accessories &
Performance Specialists Since 1963

Video: Heater Core replacement for 850 1993-1997, V70 1998-2000, S70 1998-2000, C70 1998-2004


Todays Tech Tip will be tackling the problem of replacing a bad heater core. 

You'll know you need a new heater core If you're starting to smell a sweet odor, seeing steam out of the vents, or you’re experiencing a sticky film on the windshield. A bad heater core can also make it very difficult to clear your windows of fog or condensation since it's blowing moist air out of the vents.

A bad heater core can also be tough to diagnose if the above symptoms don’t show up but your coolant is always low with no signs of external leaks.

In some cars, the leaking coolant can get underneath the carpet and you won't see any visible damp signs due to the waterproofing on the back side of the factory carpet. This means the heater core can leak for quite a while before you might notice it in the interior. If you are finding your coolant level always seems to be low but can’t find any external leaks take a close look at your heater core, it might just be the culprit.

Early Volvo models used all metal copper and brass heater cores. These cores last for a long time if the cooling system is in good shape and the coolant is flushed periodically. Volvo started to use plastic and aluminum heater cores in the 850 and newer models. These cores are prone to leaking where the glue or seals fail where the plastic meets the aluminum. It would seem logical that repeated expansion and contraction of the plastic would cause seal failure long before the core itself actually failed. Also, early 850 Volvo models used steel pipes which led to corrosion. Volvo started using aluminum pipes in later 850 models. We've seen people go to yards and get these pipes as they are less prone to corrosion, thus leaking. 

Tools Needed

  • Torx Driver
  • Torx Driver Bit 15
  • Torx Driver Bit 25 
  • Torx Driver Bit 20 
  • Towels 
  • Heater hose clamp 

Parts Needed

  • Heater Core
  • Heater Corn O-rings (optional)

We have you covered if you don't have those parts. 

  • 112475 - Heater Core - P80 850 C70 S70 V70 
  • 112864 - Silicone Heater Core O-ring 
  • 124307 - Heater Core and O-ring - P80 850 C70 S70 V70 
  • 110216 - Torx 25 Driver
  • 124507 - Torx Bit Set
  • 106639 - Heater Hose Clamp 

The first step of the replacement is removing the lower kick pen under the steering wheel. At this stage, you'll be using the Torx 25 Driver to take out the screws. Once it's removed the whole piece will slide out, after which you can simply unplug the light connector. 

The next step is tucking the carpet in under the pedal this will allow you to pull off the panel to your right (there should be no resistance). You now have access to the heater core on the driver's side. 

Note: Early 850 models have pipes that lead to the heater core and they are made of steel. This is important because when the steel pipes start to leak they deteriorate. We've seen people replace these pipes with later models pipes because later models pipes are aluminum and don't deteriorate as fast. 

The process you went through on the driver's side you'll be doing on the passenger's side with a few added steps. First, you'll need to pull out the glove box. There are six Torx 15 screws around the outside of the box and an additional two screws under the lip. Once you have the screws out you'll be able to remove the bottom panel of the glove box. While removing the panel you should see another light connector, you'll want to unplug the connector and remove the panel. After that we have to remove three knee bolsters; you'll need an extension to get to them. Once you have them removed you can take the glove box out. Once removed you'll need to tuck the carpet in and remove the plastic panel to your left. You now have access to the heater core on the passenger side. 

The actual disconnecting of the heater core unit is pretty simple. There are two screws on the passenger side and two on the driver side. The screws are Torx 15 and Torx 20. To see the screws you'll need to angle yourself under the heater core. 

Before moving on you'll need to clamp the heater hoses otherwise you'll end up with a big mess. What you'll want to do is grab a pair of heater hose clamps and crimp both heater hoses. This will keep the block from draining the majority of fluid in the part. You're still going to get some spillage though, so have a towel ready. 

After the heater hoses are crimped, we can move onto disconnecting the coolant pipes from the heater core. There's one Torx 25 screw that's located between the two fittings on the bottom of the box (on the driver's side). After you have the pipes disconnected you'll need to remove the evaporator drain which will be under the heater core on the passenger side. 

Finally, we are taking out the heater core (you made it!). Tilt the heater core back and pull out toward the passenger side. After taking out the heater core you should see the heater core o-rings at the end of the coolant pipes. We recommend replacing these If they go unreplaced they can cause a leakage which can ruin the new heater core you're installing. 

Now that we have the heater core out we are going to disassemble the unit. At the bottom, you'll want to unscrew four Torx 15 screws. 

Volvo Enthusiast Moment

Based on how brown your heater core is, is a good sign of how bad it is. When the car is in use there's hot water running through the heater core which will eventually turn it over time. 

The installations portion is pretty simple you'll wrap the foam strip around the heater core. This is essential because it forces air to go through the heater core. For the placement of the foam strip you can just mimic the placement of the old one. Once placed you're set to install the new heater core. When you're going to reinstall the heater core a necessary rule of thumb is making sure the heater core box is lined up with the coolant lines. 

A good mechanic will turn the car on and heat cycle the car to check for leakage after installing the new heater core. That way you don't run the risk of completely reassembling everything just to take it back off. Make sure to remove the heater hoses before starting your car. 

Reassembling will be the same process in reverse so: heat cycle, refill coolant, install plastic side panels, tuck back carpet, knee bolster the box back in, and screw in your glove box. Don't forget to plug the light connector back in on the driver and passenger side. Make sure to consult owners manual for specifications regarding coolant. 

Ipd is not responsible for any incidents or accidents that might occur when doing this installation. ipd is providing a simple and quick how-to installation guide as a reference. 

If you're unsure of the information provided in this video please consult with a professional before proceeding.