DIY: 1998 Volvo S70 GLT Heater Core, Heater Hoses Rebuild!

[dosbricks]

I would theorize that the cause is either vibration or movement transferred through the hoses that are now short-hooked to the aluminum pipes.

I used the ebay cores and o-rings on both cars. Replaced the firewall coupler on the S70, but it looked good, so only did the core on my wagon. No leaks on either.

[cn90]

I made a simple sketch re O-ring, this is generic stuff re O-ring.
- In the recess (in the heater core), the depth is important: if the recess is a bit deep (we are talking 1/10mm here), the O-ring iwill be somewhat loose (not squeezed enough), so it will leak under pressure.
- Or the O-ring may be a tad too thin, again maybe 1/10mm thinner than Volvo O-rings (just a theory).

- By having an extra copper gasket (or something similar such as plastic ring found at firewall coupler), the O-ring is squeezed better, fixing the leak.

I understand some people get away with the ebay O-ring and some have leak using ebay O-rings.
I knew about this ebay O-ring leak from another forum, someone had the exact same problem as mine: leaking ebay O-ring, he fixed it by adding the plastic ring (found at firewall coupler).

Anyway, photo below...

[precopster]

I'm about to do this for a customer with non turbo 99 V70 using heater core from ebay (through seller volvonest) and a gutted coupling because his radiator cracked causing system pressure on heater core which exploded so I'm also replacing ALL cooling hoses. With local radiator pricing over $350 (Hella-Behr) the whole job will come to just over a grand because of postage/parts costs. I'm using Gates lower radiator hose 22253.

Our local parts stores don't sell Gates hose for the heater core bypass so I went to our local specialist rubber seller called Clark Rubber and they sell Goodyear 5/8 heater hose which is claimed to be EPDM in construction and bought 1.5 meters. Is the Gates hose EPDM??

[erikv11]

... his radiator cracked causing system pressure on heater core which exploded ...

I can't figure out why a cracked radiator would mean cause anything other than *less* pressure on the heater core, strikes me more like a head problem or cooling system clog is at fault, can you elaborate?

[mecheng]

@dobsbrick has an interesting theory, I would make sure they are well supported at the firewall with the self placed rubber.

What about adding two o-rings together? Seems much simplier.

[precopster]

@Erikv11 Car loses coolant, car engine overheats causing steam pressure within cooling system, heater core vents (weakest link) before coolant cap does.

Car now has new radiator, fitted today. Heater core is still bypassed until new core arrives. I performed a combustion gases leak test using dye and looks OK.

Fitted new lower radiator hose Gates 22253 which arrived from Amazon over the weekend (gotta love priority shipping!!), new upper hose, new thermostat (Wahler 90deg) and new Stant pressure cap

Was testing until 6pm this evening and allowing coolant to reach 105 degrees C and fan kicks in on cue. No excessive pressure in the system. All looks good from here. Hope the head gasket isn't compromised but I guess time will tell

[erikv11]

I see, so there has to be so much steam pressure that it can't get out the crack quickly enough, and builds up in the system. Thanks.

[dosbricks]

@dobsbrick has an interesting theory, I would make sure they are well supported at the firewall with the self placed rubber.

What about adding two o-rings together? Seems much simplier.

One O-ring could just squash past the other.

I'll propagate my theory a bit further. Even if the hoses are solidly supported at the firewall but they are hanging between the engine and firewall (weighted with coolant) the firewall is going to serve as a fulcrum causing the hoses to exert upward pressure on the pipes in the passenger compartment. Which could allow a seep leak at the lower edge of the o-rings. They're already under tension from having to make a bend downward to attach to the cut-off pipes.

Gosh, I believe I could get a mystery thriller out of this if I fluffed it up a bit.

[cn90]

- The hoses are supported by the plastic coupler @ firewall and the caulking material. Plus this is no longer aluminum pipes that run the length, it is mostly flexible hose.

- The Torx 25 bolt is the one that holds the pipe assembly (the black plastic block) tightly to the heater core.

- The coolant leak is fixed by a combination of: copper gasket (mentioned above) + Volvo OEM O-rings.
I have no leak now. So the cause is either:
a. Ebay O-ring a bit thinner than Volvo O-ring...or
b. Heater Core recess is a bit deep. Remember that this is aftermarket HC that may or may not come with proper spec (i.e. how deep the recess is). This explains why some have and some don't have coolant leak using the supplied O-rings.

[cn90]

I finally found the thread with the same issue like mine (implying the ebay heater core recess is a tad deeper than spec).

See the thread by "g00b86":
http://volvospeed.com/vs_forum/topic/15 ... ter-cores/

...I'm a month in on mine. Looks quality for the price. My only advice is to test fit before you install their foam strip since its just barely enough, and to get better O-rings. I used brand new OEM O-rings and it still leaked. Fortunately I bought the wrong kit for the firewall coupler And I was able to place those yellow plastic spacers behind them and everything has been perfect.