C70: Slow Coolant Leak - B5244T

[Volvophile]

Hi guys,

Our 2001 C70 2.4T has recently required topping up of coolant. I am trying to decipher whether it is the water pump or heater matrix. I previously subscribed to the theory that Volvo water pumps were bulletproof and no OEM replacements would match their quality, so I left well enough alone. The air vents have long had a smell coming through also, which can sometimes indicate heater matrix failure. I have however encountered this a trait on other P80 platform cars. There is also no significant fogging of the windows that would indicate this.

I was considering to try ordering a new water pump and replacing that first. At least if it is found not to be the cause, it will have a brand new water pump.

Is my logic sound?

[ITSv40]

Originally Posted by Volvophile

Hi guys,

Our 2001 C70 2.4T has recently required topping up of coolant. I am trying to decipher whether it is the water pump or heater matrix. I previously subscribed to the theory that Volvo water pumps were bulletproof and no OEM replacements would match their quality, so I left well enough alone. The air vents have long had a smell coming through also, which can sometimes indicate heater matrix failure. I have however encountered this a trait on other P80 platform cars. There is also no significant fogging of the windows that would indicate this.

I was considering to try ordering a new water pump and replacing that first. At least if it is found not to be the cause, it will have a brand new water pump.

Is my logic sound?

I would investigate the heater matrix first. They are a known issue and would cause the cabin smell. The water pumps are generally bomb proof - I have had pumps cover 270 and 370,000 miles and still be good. In both cases the body rotted first. If the water pump is leaking there will be a white stain down the rear of the block by the timing belt. This can be checked without dismantling anything.

[Luxobarge]

Seconded - of the two, heater matrix would be strong favourite. Check thoroughly for damp around it and the carpets underneath.

other possibility is radiator failure, allowing coolant into the oil cooler section of the rad (assuming yours has the oil cooler at the right hand end of the radiator arrangement) - check the oil level and that the oil is clear and transparent, i.e. not starting to go cloudy. Having said that, if this is the problem it's more usual to get oil in the coolant, not the other way around. My money's on the matrix.

[Baffler]

Originally Posted by Volvophile

The air vents have long had a smell coming through also, which can sometimes indicate heater matrix failure. I have however encountered this a trait on other P80 platform cars. There is also no significant fogging of the windows that would indicate this.

Any wiff of coolant in the cabin is a clear indication of a leaky matrix. The soundproofing underneath the carpet is high absorbency sponge so it's only a matter of time before the windows start to fog up. Usually falls towards the passenger side. Act asap before it fills with coolant!

Apparently, going off a recent thread on the same subject, the matrix is no longer available from Volvo. Lots of poor replacements out there with low flow rate, leading to poor cabin heating but Behr/Hella were OEM suppliers. I got my last one from a German auction site and it was identical to the original with just the Volvo logo ground off. It came with a length of sponge included but no Orings.

I hear good things from other members about Nissen radiators but I've no experience with them.

[Baffler]

Found an older thread by Cookeh: Heater core ...see post #13 from SwedishBus who reckons, at the time, the PFS supplied part is better made than the original as it has brazed cooling fins.

There is also a 42mm and 48mm MAHLE core available from Auto-Doc, the 48mm producing higher output, but I can't see a 48mm with brazed cooling fins.

[Volvophile]

Originally Posted by Baffler

Found an older thread by Cookeh: Heater core ...see post #13 from SwedishBus who reckons, at the time, the PFS supplied part is better made than the original as it has brazed cooling fins.

There is also a 42mm and 48mm MAHLE core available from Auto-Doc, the 48mm producing higher output, but I can't see a 48mm with brazed cooling fins.

That's great, Liam.

Thanks for the information, it is appreciated. I will certainly look into that.

[Baffler]

You're welcome, Volvophile, hope you get it sorted!

Another source of a slow coolant can be the lower rubber hose of the expansion tank where it joins the metal pipe at the rear of the engine. Sometimes swelling of the hose can occur allowing for a build-up of fur and any coolant lost here is burnt away by the hot manifold.

[Bigfella666]

Or you could take my approach

Coolant leak started 5+ years ago and to this day I cannot see any strteaks of white dried coolant anywhere

So I took the PNutt approach - fill up with deonised as and when and bingo problem solved

And yes he was spot on the money. To this day filling up every 2-3 months on 5000 miles a year, still cannot find leak !

And yes matrix replaced 5 + years ago so can rule out that as a cause

[Simmy]

pin hole leaks on the side caps of the rad that only leak when under pressure is another common one.