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hey people,

got a quick question regarding flushing the radiator ...am planning on doing this later tonight coz when I bought the car ...came filled with just tap water and from the looks of the cap-off & also overflow reservoir...it's brown with rust.

i'll run a hose through the top and let it wash out. Question is when I refill the radiator ..assuming i do this with the engine running so the thermostat opens up...is there a spot on the engine where I need to bleed the air out of the water system? ..know that on honda vtech and other couple engines that you needed to do this.

not that i know of.

after draining and flushing the radiator i would recommend to refill with plain before adding the coolant. this will prevent everything getting dirty if the radiator erupts severely while burping, so yea the air is bled by keeping the cap off with the engine running and filling with water as necessary.

once the water stays clean enough you can drain and add your good coolant in.

Hi.
If you can have the front of the car higher than the back as air always travels to the highest point. As long as the system is clean and from your post it is probably dirty you can add the water and coolant to fill the radiator start the car with the cap off and warm it up until the thermostat opens you can tell by feeling water running through the top hose.Once the thermostat opens you may have to add more water with the engine running. You will get hot water coming from the radiator and when no bubbles are present put the cap on job done.
If your system is dirty fill with clean water let it warm up(hot) and drain the water. You may have to do this several times until the water looks ok then do the coolant. Don't forget to have the water in the overflow bottle at the correct level and don't put cold water in the engine if it is hot- start the engine before adding cold water.

Make sure you're seeing good flow across the top-tank of the radiator. If the engine has been run without rust-protection for awhile you can get serious flow issues which will mess up your cooling for obvious reasons.

remove top hose and bottom hose, assuming its an nb8b this will be the two hoses.

run distilled water through the top hose with the car off.

once its all coming out clear then run coolant through it.

one u see coolant come out then reconnect the hoses and fill with a mix. i use 70/30 to prevent electroysis and corrorison.

once you start up the car make sure the front of the car is jacked up and let it burp itself out.

you will need to wait unitll the thermostat opens let the fan come on 3 times. then fill the overflow and enjoy your cool car.

hey Narita,

wouldn't running water through the top hose with the car off, just spill out again due to the closed thermostat?

^precisely the point, isolates the radiator to flush it out. If its rusty you dont want to dislodge the corrosion and pump it around the engine.

Although if you radiator is rusty I would be replacing it.

Sorry I forgot to mention you remove the t/stat.

Reason being as you can flush the rad alone but then you may not know what is in your engine, not to mention you could mix coolants and have no idea of your ratio.

ok..makes more sense that way..lol

Open the car's Heater, makes sure cleans through all piping.

I don't think anyone posting here has ever dealt with a seriously rusty system.

I did a bad BP engined Mazda Astina once. Basically I split the job into 3 parts: engine, heater and radiator and cleaned them separately.

The heater was first. Disconnected the two hoses from the engine and connected two garden type hoses to the inlet and outlet pies. Ran tap water through it, alternating direction every few minutes, with the waste end running into a big white basin until it ran clear in both directions. Took about 15 minutes of flushing, used probably 500 litres of water and flushed out about a cup of rust flakes.

Radiator next. Removed from car and gave it the same treatment for another 15 minutes. Another cup or two of rust.

Engine next. Removed thermostat and kept alternating input between top hose, bottom hose, back of head and back of water pump with outflow usually limited to only one of those. Letting it partially drain between changes let air in which actually helped with agitation. Another 30 minutes and another cup or two of rust.

I failed to clear all the small hoses in, around and under the inlet manifold. They were so solidly blocked that I had to replace all those and also dismantle and manually dig the rust out of the idle speed control system.

All up I used maybe 1-2,000 litres of water and ended up with half a bucket of rust but we didn't have any cooling problems with it again. Don't tell me BP engines aren't tough! Try doing that with little bottles of distilled water.

My old man also uses a hose but has it setup so it pushes on to a metal tube that has a tapered plastic bung similar to that from a science lab put over the end and bike valve holder and valve soldered in.

Allow him to use a compressor to blow air in with the water supply and gives heaps more agitation. Again thermostat removed for this process.

Bleeding, either jack it up, or cut the bottom of a coke bottle, wrap the next in about 8 runs of electrical tape and jam it in the radiator. This allows you to overfill the rad a bit and guarantee the radiator is the highest point. It also allows the overfill to be sucked down when air comes out.

I just did mine and put the water in when the engine was cold and off so obviously got a lot of air out before it settled down.

As previously said, make sure your heaters on to get the coolant in and air out.

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Water flow to the heater is permanently on with an MX5. It's part of the engine cooling design. The heater control only varies the amount of air flowing through the heater core.

Thanks manga_blue good to know.

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thanks heaps for the reply all.