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740 Heater Core Replacement (Pictures)

The Turd

New member
Nov 9, 2015
Hey everybody! New to the forum. I replaced the heater core in my 91 745 turbo last week, I guess you could say I'm a proper Volvo owner now lol:cool:. Here's some pictures that I took of the process.

Time to remove the core was 3.5 hours. Total time was probably around 12 hours over 3 days because I removed all of the carpets to pressure wash them.

Tools you will need:
7mm and 10mm 1/4 inch sockets
1/4 inch extensions
Universal joints
Socket wrench
10mm wrench
7mm ratcheting wrench (not necessary but very helpful)
Plastic pry bars (for interior pieces)
Philips and Torx drill bits.
Drill + small drill bit
Various screwdrivers
Sealant for heater core box
Brass plumbing elbows
Small hands
Small phillips screw (For replacing the rivet)
4 cups of coffee
Cigarettes (optional)

First I bypassed the heater core with some brass plumbing pieces. (and disconnected the battery of course)

Then I took out the center console

Then the glove box

Then the ash tray and center storage/cig lighter assembly

Stereo and its housing (phillips screw deep in there)

Now you can remove the center side panels and the kick panels

Unclip the relay tray and move it to the side

Remove the heater control panel, make note of wiring and vacuum lines

Here's where the fun starts. Start removing ducting. Its a fairly strong plastic and can handle twisting and pulling.

Rear floor vents removed

Drill out the rivet on the distribution box and remove. Remove rest of floor ducting

Here's the heater core box. There's about 11 7mm bolts around it

Box is removed. Getting those bolts out took me about an hour

Closeup of heater core

Core is out yay

Old vs new. Idk why the company painted the new one silver. It's a Spectra brass/copper core ($70 on rock auto)
I have the sugary smell in my 1990 740 so it'll be my turn to rip my knuckles off soon! I did a 940 and a 240 in the past so I know what I'm getting into! :nod:
I've had the utter pleasure to do 7 of these in the last 18-24 months.

fwiw, if for any reason you pull your dash (replacement, better color, etc), DO THIS regardless whether its officially leaking or not. The last 3 I pulled was for that reason alone and all of them had green streaks on the seams or had started to weep. I'm prepping to swap a gray interior into a 940 in about 2 weeks and will do this again. With the dash out of the way its a 45-60 min job.

Break it on your terms as they will never fail on a sunny 75F day either.

Nice job on the write-up. Brings back some fond memories of mine... not. The only positive thing I remember about doing that job was discovering some good new music on Pandora playing on the background.