Rover SD1, Heater Core Flushing

I’m having a frustrating issue with the Speeduino install at the moment, so I took some time to try to fix my non-functioning heater.

Since I got the car one of the many things that hasn’t worked is the heater. It would only blow cold. It didn’t appear to leak, and the flaps moved when you moved the lever, so the only thing that could be left was a blocked or gunked up heater core.

Since the cooling system was already open and drained from the Speeduino install, I thought now was a good time to try flushing, and back-flushing the core.

I purchased a few meters of clear hose from Bunnings a while back for this job, so that I could do it in the garage and run the hose into buckets to collect what comes out of the core and safely dispose of it.

I chose to use the heater hose where it connects to the waterpump, and on the other side of the core, the hose that goes into the under intake pipe. 

This allowed direct connection to both sides of the heater core, so with my garden hose in hand, I began forcing water into the WP side of the core. The first things I noticed was when I took the hose off the water pump, there was very little coolant in the hose, and it actually had some rusty gritty stuff in the hose. This is what the clear hose looked like after I poked it in the end of that hose.

Clearly it didn’t have the flow of coolant I would expect. The other thing I noticed was when I first turned on the hose, it took an awful long time for anything to start coming out the other hose, far longer than I would expect, and when it did, it was pretty gross stuff. There was no trace of the bright green anti-freeze that’s in the rest of the system, it was just muddy brown muck. This is what was in the bucket the first time around.

I then swapped sides, and reverse flushed the core, pushing water in from the other side of the core. The water coming out was no better this way, but it did eventually clear up and run clean. I had read on the internet that filling the core with white vinegar helps to break down the crud that is sticking to the inside of the core, so, in went half a bottle of vinegar (about 1L). I gave it a couple of minutes, and then flushed again, and sure enough, more gunk came out.

Obviously with the car still in bits I can’t test the heater, but to me it appears that it had a lot of crud in the core, and may have been blocked too, so hopefully now the heater will function (and make bleeding the system easier). Should be good for winter.