Hi all, I am having heater issues. My old heater core blew a few years ago and had not bothered to replace till a couple of days ago with a tested second hand unit (which I saw being done). However after just a few minutes driving it is now leaking too. This makes me wonder if my heater hose routing is the issue. My current setup is a relatively stock 350 with a performer manifold. The large dia pipe runs to the rhs (passenger side) of the manifold, and the small dia pipe runs to the top of the water pump. There is a plugged port on the LHS of the manifold which I could use, although clearance from the waterneck is tight.

Will the fact I am plumbed directly to the water pump be the issue? Also can the cores be repaired easily? These are not common cars here and it took me a few years to come across the one I just killed :-(

Thanks in advance.

 

The heater core is nothing more than a small radiator. It doesn't care which direction the coolant flows through it. even with pumping forces, the differential pressure across the core shoudl be negligible, therefore, the core is really never subjected to pressures any higher than overall system pressure.

What possibly happened to the core was stress. It was likely tested by filling with a liquid, applying some pressure to the liquid, and waiting a period of time for the unit to reveal leakage. That's all good, so long as you are only going to fill yours with pressurized liquid. Unfortunately, you're more likey to constantly pump liquid through your's, and subject it to daily heat/cool cycles that will add stress, expand and contract the metals and solder joints, and tends to flush away any deposits that may be plugging those seeping joints.

They can be repaired, and are generally not worth the trouble. However, in your situation, it may be worth shopping around for a respectable shop and at least securing an estimate.

FWIW, a new replacement is $19.99 US, and weighs 3.4 pounds. I know it's starting to get cooler, so if you decide to ship one, better hurry. For example, from here to Christchurch 8030, UPS 7-day shipping is $92 US. 4-10 day U.S. Postal Service shipping would be $25.55 US. That makes it a $50 heater core at the end of May. If you can get a repair for that much, you can do the math.

 

Thanks for the info Vader. I thought that the system should be under the same pressure allowed by the radiator cap but it seems querky that it should burst within just a few minutes running time. The radiator shop waterblasted it and then pressurised with air whilst submerged in a water tank. Couldn't see any bubbles. Maybe I damaged it putting it in as it was a tight fit.

Have you been over this way before?

 

I've been "that way", but only within about 7,000 miles.