5 replies to this topic

[Tumbleweed-Connection]

Hi all,

 

Ok - so the same old topic that has been discussed a million times on this forum before....my heater is not blowing any warm air. However, this is after I have followed all your helpful advice over the bank holiday weekend (and having sprayed hot coolant all down my arm in the process!).

 

Over the weekend, I decided it would be a good opportunity to get on and flush the heater matrix and drain the coolant while I was at it. I did as suggested and removed the inlet and outlet pipes from the bulkhead and flushed the matrix itself first - the indicator that there was an air lock in the system being that the inlet went cold soon after the t-section where the coolant recirculates into the heater inlet. Having flushed the matrix both ways with the valve open (and the valve does move, because I also checked this beforehand), I then removed the bottom hose of the radiator and flushed the entire system by placing a hose pipe into the expansion tank.

 

So, next was to fill up with new coolant and watch as my heater now sprang into life....unfortunately, it didn't. With the engine running, header tank cap off and the thermostat open, I noticed that the inlet into the bulkhead was still as cold as it was before. So next I moved into the passenger footwell and slightly eased off the inlet pipe from the bottom of the heater assembly to create a small gap for any air to escape. This seemed to release quite a lot of bubbles and the pipe became very hot. The outlet was remained cold though, so I moved back into the engine bay and again eased the pipe away from the join to do the same. Unfortunately, this is when the entire hose came off and I got boiling coolant all down my arm. After some swearing, I topped the tank back up and started the process again. Things seemed to get hot again after some further messing around, so I assumed that was job done.

 

Last night, I was starting the long drive back home and decided to test that everything was still ok. The heater was warm for a while, but not as much as I would have expected. After a short while having the blower on, It soon went stone cold again. I checked the temp of both pipes in the passenger footwell and although the inlet seemed hot enough, the outlet had become only mildly warm again.

 

Having followed all the excellent advice on here to the letter - what do you guys think I should do next? I assume no problem with the thermostat because the water is hot enough into the matrix now. Should I have a go at slightly easing off the outlet in the engine bay again to see if I can release some more air? It seems very temperamental, so I assume it shouldn't be this much of a chew normally to remove any air in the system? The only thing I can think of which might be causing air to get back into the system is that there seems to be a small water leak, which having checked does seem to be coolant. Not had the car on a ramp, so I'm not sure where this is coming from - but it may be the water pump. Or maybe I just haven't bled the pipes enough after all.

 

Any advice you can offer would be greatly appreciated. Mine is a 2000 Cooper.

[spiguy]

Sounds like the return hose from the heater to the radiator has the blockage. When you flushed the matrix, that seems to have established that there is no flow issue through the matrix itself (assuming you got good flow in and out). The next part you did, confirmed what you probably already knew - that the main cooling system is flowing with out a blockage. However flushing through from the expansion tank to the bottom hose, doesn't really ensure that the path is clear from the matrix back to the radiator.

 

You could detach the outlet hose from the matrix, and flush from inside the car with the garden hose. I'm not that familiar with the plumbing on the MPi, as I have an SPI, but when I did this I removed the thermostatic switch at the bottom of the radiator (not sure if you have one of those) and also removed the rad cap. When flushing from inside the car, the flow of water was into the heater outlet hose, back to the radiator and out the hole where the thermostatic switch goes. I think you need to do something similar - ie find a route to flush whereby you are sure that the flow is actually going through the matrix to radiator return pipe.

[Tumbleweed-Connection]

I can't say I see any thermostat near the radiator, but that's just from memory. The slightly frustrating thing is that the reason why I left it until the weekend was because I was going back to my parents house and they have all the gear I needed. I live in a flat, so don't have a hosepipe to flush with again, or anywhere to attach it to even if I did    I can see what you're saying about the return not getting any flow through when I flushed though, which is why I flushed the matrix specifically rather than just relying on flushing through the header - there is no rad cap on an MPI. There was a nice bit of brown came out when I reverse flushed and then ran clear soon after, so I know the matrix should all be squeaky clean.

 

When I flushed the matrix, I went both ways to be sure and had a constant stream of water, so perhaps the blockage is further down the chain, as you suggest. It did all get hot for a while directly afterwards, so is there any reason why it would just go cold again having been warm?

[Steve220]

The method you have described as flushing the entire system doesn't touch the engine at all. You have only flushed the radiator and matrix.

To flush it fully I would advise removing the thermostat housing and running hot water through the expansion tank, this will fill the engine up from the bottom and pour it out the top. If you don't want to get the engine wet then remove the thermostat and put the housing back on remove the top rad hose, keeping it upright to prevent it coming out the radiator. the only true way to flush the heater matrix is to remove it I'm afraid. Once I had mine out I couldn't believe how much rusty gunk was in it, it also allowed me to fill it with detergent and shake it to remove any oily deposits.

[Tumbleweed-Connection]

Well I have to say, I'm pretty much an amateur when it comes to anything technical, so I'm not surprised I got that wrong really in thinking I'd flushed more than I had. I did think that everything ran out rather quickly. Wasn't all that much point doing it in the end because aside from the dirty brown stuff stuck in the matrix, everything else was pretty clean. Removing the whole matrix would probably be a job for another day, which is a shame really as I honestly thought I was close to having it working!

[spiguy]

It's not that hard to get the matrix out, there are only a couple of screws holding the heater box on to the lower dash rail, then you just back of a couple of nuts that locate it at the back - it sort of hangs on a threaded rod with hooks.