2000 S70 Coolant Slowly Decreasing

[scot850]

MoVolvos is correct. The heater core continues to move water even when turned off or to cold. The leak will continue.

Neil.

[abscate]

You won’t get wet carpets in a p80 for a long time , as there is so much padding underneath. Throw in a gallon of premix into the trunk, have a piece of 5/8 heater hose and two hose clamps so you can bypass the heater if needed, and roll Tide…or Spartans or Mountaineers

Keep an eye on that coolant light for trip

[tjmartin317]

When you did the heater core replacement, I’m guessing you also replaced those two little o rings going into the housing, yes? Am trying to procure parts and tools in a day, and will likely have to get those from Volvo themselves unfortunately… hoping they have em in stock.

[abscate]

What I do on this job.

Pop out the two heater hoses from the firewall. Make sure you get all the orings and spacers in the end and either recover them or hold them in place with a spare oring or tape

Now flush the heater core with fresh water from a hose. When you release the core inside the car about 500 ml of water will spill which you can catch in a garbage bag positioned underneath and not have a sticky mess to deal with



The orings and their sizes are documented here and you can use standard sizes here.

Any oring you disturb on a 20 year old car gets replaced.

Searchable under ‘ master o-ring ‘

viewtopic.php?t=88579&hilit=O+ring

Courtesy of Scarlson

I have one!

Heater core to heater core pipes. Volvo part number 3545586.

It's actually an inch size, not metric! Officially defined as 20.78mm x 15.54mm x 2.62mm, this corresponds to a -114 (dash size) or 5/8 x 13/16 x 3/32 inch nominal size, or 0.612 x 0.818 inch actual size.

Buna-N and EPDM are pretty equal for coolant applications, having equal resistance to ethylene glycol and both tolerating temperatures the coolant is likely to reach. A generic hardware store o-ring will suffice for this job. Hopefully this should get someone out of a pinch (literally, perhaps, if they pinch the o-ring!).

I did a ton of research about this because I had a leak at a newly-installed heater core where it joined the pipes. It was a MTC brand heater core from IPD. Turned out it was defective, one of the o-ring bosses was misshapen and would never seal!

[tjmartin317]

Can you help me confirm if this kit has the o-ring I need? I think A114 is the part number.

https://www.harborfreight.com/180-piece ... G4QAvD_BwE

If yes, then I'm banging this out tonight before we set off to Michigan (well, first Ohio, as that's our overnight stop).

[volvolugnut]

In the olden days when cars were ancient, you could block off or clamp the heater hoses to stop leaks at the heater core. I don't know if that is possible with your car.
Does the carpet smell of antifreeze? If not, it may be rain water from an outside leak.
volvolugnut

[P80GLT]

O-rings are still available direct from Volvo, they're not expensive and guaranteed to fit

Part number on image below

O-rings.jpg (59.25 KiB) Viewed 280 times

[abscate]

I don’t think that Harbor Fright kit will fit. See sizes above

[Chuck W]

I would suggest to NOT fiddle with the heater hoses on the firewall unless you plan on more work than just replacing the heater core. You may get lucky and not break things, but more often than not, you will bust the bulkhead and have to replace that as well.

Just drain the cooling system and have a bag under the heater core when you undo the fitting holding the tubes into the core. Yeah, you get coolant instead of water, but seeing as you're in a time crunch, I would just do the necessary steps (draining the cooling system) and not risk other "problems".

The heater core should come with new o-rings. At least the 3 I've purchased have.

[tjmartin317]

No new seals with my Autozone heater core... yeah, you can wince, but in a pinch they had the part I needed at a very good price... it could be the wrong part though.

Went on a 45-ish minute drive, maybe a little longer, all highways. Marked where the coolant started. Obviously the system got hot and things expanded. Now I'm eagerly awaiting the end of the day to see where the level sits once cool. I had a little "catch can" under the core, and there was a thin film of coolant, but no puddle or even a drop...

If I had found this yesterday I would've been golden. Seals and all ready to go. But those damn seals prove impossible to find in a hurry.