Postby busheytrader » 13 May 2015 20:27
Hi,
It's unlikely to be the matrix itself but the rubber seals to the matrix. There are 2 mild steel pipes that take the water into and away from the matrix. These are a push fit into the matrix itself, the rubber seals acting as sleeves around the pipes.
The mild steel pipes eventually rust beneath the hardening rubber sleeves breaking the seal and hence the leak. Mine let go with a violent escape of steam enveloping the cabin. A few years ago the fix was to install replacement pipes in stainless steel and new old stock rubber seals. The rubber seals then became unavailable. A new matrix with rigid metal tails is the latest fix.
Unfortunately the matrix is buried in the heater box which in turn needs the whole dashboard and console to be removed. It is a long job that's more fiddly than difficult but if you search the forum there are several contributions including one from me and another from Beans.
Short term for the Summer you can bypass the heater in the engine bay by forming a "u bend" with some copper pipe between the rubber hoses that pass through the bulkhead. I did this successfully for several months.
Hope this helps,
Adam

TR7 V8 DHC Jaguar Solent Blue. 9.35cr Range Rover V8, Holley 390cfm, JWR Dual Port, Lumention, Tubular Manifolds, S/S Single Pipe Exh, 3.08 Rear Axle, 200lb Spax & PolyBushes all round, Anti- Dive, Strut-Top Roller Bearings, Capri Vented Discs & Calipers, Braided Hoses, 4 Speed Rear Cylinders, Uprated Master Cylinder & Servo, AT 14" 5 Spokes or Maestro Turbo 15" Alloys, Cruise Lights, S/S Heater Pipes, Replacement Fuel Tank. No Door Stickers. Mine since July 1986, V8 from 1990 courtesy of S&S V8 conversion kit (built not bought) and big brake kit.