How to flush my cooling system?

Flush it through with a hosepipe & then radflush it a few times. It'll never all come out but it'll stop giving you grief.

I don't think you've done anything wrong. People like to sneer at such things, but it's not really that bad. And I don't think that a can of radweld is enough to give you the blockage you describe, it's rusty gunge and would have been there anyway. When you come to think about it, how much stuff was there in the can? Not enough to coat the inside of your entire engine *and* block the hose.

At least it's summer, so no freezing up problems. I would just give it a hosing out and refill with water, then drain and refill a couple more times over the next few weeks to get all the gunge out. Then when it comes out fairly clear, you can refill with antifreeze mix before the first frost.

HTH

Steve

The return hose starts with a short small diameter rubber hose from the top of the radiator, which then gos into an even smaller diameter plastic hose. It is at this point where it has backed up. I think the viscosity of the sludge was too much for it to flow through.

Sadly I'm in the South East. Even though my water is metered, if I get a hose out no doubt I'll be shopped quicker than you can say "hosepipe ban".

One other thing. I did initially panic that it may be a head gasket problem. However:

- No water has got into the oil. No sludgge of any sort on oil cap or dipstick. - No other problems with the running of the car. - The colour and consistency does not look like any oil & water mix that I've seen before. It is a lot darker and is not at all frothy. The water has been colured (presumably from rust within the system), and the sludhe is consistent with that of rust & the Radweld itself.

However, is head gasket in someway still a possibility?

I'm still pretty convinced that it's the Radweld. Simply flushing with water won't shift it. Particularly as I can't use a hose.

I was thinking that I could get something like Speedflush perhaps? And run in the system, drain, and repeat. Would this be good enough to shift a majority of it?

Possible, but unlikely, unless there are other symptoms you haven't mentioned. What kind of car/engine is it by the way?

And this "return" hose, it goes from the top of the rad to where? to the expansion tank? This sounds like the hose which purges any air from the top of the rad to make sure the system is full of coolant. I would call it a bleed hose, but let's not argue over terminology. The arrangement you describe is very prone to getting bunged up with gunge at the narrowest point, it's not your fault or the radwelds'

Steve

I've got to agree that radweld shouldn't cause that amount of sludge.

It doesn't happen to be a diesel fiesta by chance?

Depends where in the SE. There are two levels of restriction, an ordinary drought order (the so-called "hosepipe ban") and the much more stringent emergency drought order.

Unless you are in an area where an emergency drought order is in force, the only restrictions are that you cannot water the garden directly with a hosepipe, and you cannot clean your car with a hosepipe.

It is perfectly legal, for example, to water an *allotment* with a hosepipe, use a hosepipe to fill a watering can, or clean a driveway or patio with one.

I'm sure flushing your cooling system would be perfectly legal if only a "hosepipe ban" applies to your area.

HTH

Chris

It is a 1990 BMW 535i - The 3.5 M30 engine

I'm not going to pretend to be a fountain of knowledge as far as cars are concerned (far from), however there does seem t obe a constant flow of water through this pipe. I was told that Teransits work in a similar way too.

It is a 1990 BMW 535i - The 3.5 M30 engine

I'm not going to pretend to be a fountain of knowledge as far as cars are concerned (far from), however there does seem t obe a constant flow of water through this pipe. I was told that Teransits work in a similar way too.

Great! Not only is the Radweld definitely causing problems (yet anoth blockage), but it does look like the fan clutch needs relpacing also.

I am in the process of flushing it, but now I need another fan clutch rather rapidly!

DOH!!

OK. Update:

I have replaced the fan clutch. I have also flushed the system through with some speed flush. Man, loads of crap came out.

The return hose was well and truly blocked, as was the expaansion tank where the return hose fed into. All unblocked now though.

Ran a hose through until the water wasn't so brown any more.

It is fine now. No overheating. Stays on centre.

Have added another bottle of speedflush. Will then flush through again next weekend. Hoepfully most of the radweld sludge will have been removed once I have done that.

Bloomin' typical. Two different problems both at the same time. Pah!

Hopefully that will be the end of it now.

Thanks.

Wow! This is really proving to be a proper pain. I have changed the fan clutch & thouroughly flushed the system through. All has been OK since.....

Until yesterday. Now it keeps getting hot in traffic, but the temp drops again when on the move and a sensible pace.

I have ordered a new thermostat & water pump. Hopefully this will be the end of it. Thoughts?

Man! How expensive are the thermostats for these things too!!!!

Check the electric fans actually happy & blowing the right way.

There is no electric fan. I do not have A/C.

Backflush it again then. You've changed the fan clutch so unless you've bolted the fan on back to front , which IIRC, is practically impossible then either your thermostats buggered/clogged or your radiators buggered/clogged. Or the impellers come off the water pump, but it'll overheat at speed if that happens.

Well I received new water pump & thermostat on Monday morning, so replaced them on Monday night.

I'm still convinced that it was the water pump that was the problem, but could see no obvious faults with either.

Anyway, fingers crossed, it's been OK since. But after changing the fan clutch & flushing it was OK for a week or so.

Will keep an eye on it, and post back here if problem re-occurs.