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300tdi coolant flush and renewal help?

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Hi there,

Got some time off work this week, so thought I'd tick some jobs off on the old girl.

Anyway, ive been planning on flushing the coolant system for some time now, as looking in the header tank looks weak - rusty coolant, as well as having no heat from the heater. But, i havent really found the best way of doing it. I didnt really fancy removing the radiator or any of the cooling system really, especially with no fan spanner.

After doing some research, i noticed some people have used a coolant flush chemical of some sort, similar to holts rad flush. Would this suffice and be up to the job and successfully clean out the cooling system? I have no cooling/temperature issues at all with the 300tdi, just doing it as routine maintanance.

Im also abit unsure on what to do?

Should i remove the top and bottom hose off the radiator, drain and Flush out with a hose pipe. Then remove the drain plug on the block, and heater matrix pipes and flush all through with a hose pipe?

Does this sound correct and have i missed anything?

Any help would be massively appreciated, i want to complete the job myself, but what to do is very vague despite searching.

Thanks in advance

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I tend to just flush both the block, the heater and the radiator seperately, doing them all in both directions a few times using the hose pipe. This way it removes all the old coolant and maybe a bit of accumulated gunk. All that should be left in the system when done is clean fresh water. Then re-plumb it together and add a bit of water followed by the correct amount of antifreeze for your preferred mix and top up until full with water. The engine will mix it once running. I generally take it for a run and check the level afterwards as there will be a few air pockets to displace.

I've never used any coolant flush chemicals, so can't comment on those I am afraid.

I've heard the 300Tdi is suceptible to air locks in the system and has to be filled a certain way, so be sure of that before starting.

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I tend to just flush both the block, the heater and the radiator seperately, doing them all in both directions a few times using the hose pipe. This way it removes all the old coolant and maybe a bit of accumulated gunk. All that should be left in the system when done is clean fresh water. Then re-plumb it together and add a bit of water followed by the correct amount of antifreeze for your preferred mix and top up until full with water. The engine will mix it once running. I generally take it for a run and check the level afterwards as there will be a few air pockets to displace.

I've never used any coolant flush chemicals, so can't comment on those I am afraid.

I've heard the 300Tdi is suceptible to air locks in the system and has to be filled a certain way, so be sure of that before starting.

Couldnt ask for better help to my concerns than that. Very greatfull again.

Have i got to be carefull of the pressure of the hose pipe? Or doesnt it really matter? I take it i shouldn't be using the sprayer on the end?

Sorry for stupid questions, im clueless with this task

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Forgot to add.. Do i need de ironised water? Or can i use tap water, which i suppose will already be in the system?

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I just use the standard Hozelock hose end, which is a reasonable fit in the 1-1/2" rad hoses, and hold it in there by hand. No sprayers. You should be OK with the pressure unless your mains is very powerful, if worried just don't open the tap fully. As long as there's a good flush through each way a few times it will do the job.

I suppose in theory deionised water would be best, but I've not done that with mine - just standard tap water. But I'm not on a mains supply so not sure what sort of level of stuff is in my water. See what the manual specifies if you want to be 100% by the book, but I dare say you will be fine with a mix of tap water and suitable coolant.

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Just a quick tip to avoid making a mess when you remove the bottom hose. I have been pretty unlucky in the coolant / front-end of the engine department so i have had to empty the system many times during the past 10 years. This method gives you minimal waste and minimal mess. Buy a short length of of 10mm inner diameter hose (2 metres should be sufficent). Use this hose to siphon out whatever's in your expansion tank. Then remove the bottom hose from the expansion tank and lift it as high as you can to avoid spillage. Insert the rubber 10mm ID hose into the bottom hose that you've just removed and push it as far down as you can. Siphon into a bucket. You should remove about 5 litres in this manner. Re-position the bucket under the vehicle, remove the plastic hose from the bottom hose and aim the bottom hose into the bucket. That way you should be able to empty the system almost completely. I have never removed the drain plug on the block because i'm petrified that it may break. If you manage to remove it, expect some spillage but at least it will be minimal compared to the amount of coolant stored in the radiator. I would buy a fan spanner if I were you. They're plentiful on ebay and dirt cheap. I had bought it thinking it was to be used once but have used it so many times since then.

Refilling the system on a 300tdi can be a bit of a PITA but be methodical and you should have no issues. Remove radiator plug and also the plug on the thermostat housing. DO NOT REUSE THEM if they're plastic (ask me why i know). I also have the habit of removing the small by-pass hose on the thermostat housing.Start to fill the expansion tank. it will take some time. Keep filling slowly until coolant emerges from the hole vacated by the plug on the radiator. Replace the plug. Keep filling until coolant emerges from the thermost housing. Replace the plug. Fill some more until bubble-free coolant spurts out of the stub that the bypass hose is connected to. Replace hose. Go for a spin, keep your eye on coolant level and temperature gauge for a few days. Theoretically, any air left in the system usually works its way out.

A final note. If your hoses are over 10 years old, replace them. Don't forget the bypass hose. I didn't replace it and I had all sorts of nasty symptoms until I realized that it was blocked.

By the way, remember to replace your coolant every 2 years, regardless of mileage. If your engine's in good nick, your coolant should still be clean when you replace it.

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I nearly posted much the same comment yesterday... If you find a bit of 8ish mm nylon airline, it will fit through the spigot on the bottom of the expansion tank, so you can syphon from the bottom hose before opening any of the hose ends.

Radiator plugs are 1/2" BSP, best ones I've found are part number 727-755 from RS Components with captive o-ring for about £4.

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Thanks very much for the replies guys. How come you advise to syphen instead of just letting it run out on the floor? And then flushing any remained in the system out with a hose pipe?

Ive already got some brass plugs for the radiator housing so thankyou for that.

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Because the very next job after dropping the coolant on the floor, always involves rolling around on the floor for some reason :blink:

And the coolant is, or can be, very bad (fatal) for pets and animals if swallowed, but because it's sweet tasting they like to drink it.

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Amen to what TSD said. It's fatal to animals and it should not get into the sewage system. It's toxic. Furthermore, rolling around on the floor on coolant is no fun at all :)

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Thanks a lot guys. More preparation that i realised is required then, to try and contain as much coolant as possible.

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When I did mine last weekend I had a tarp laid out under the car to catch the coolant that missed the bucket. This minimises the mess on the workshop floor.

Then transfer the caught stuff into the bucket with the rest and dispose of as normal.

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From one of the members on the AULRO site......

the coke bottle cooling system fill.

first prep your bottle, ok, this ones not a coke bottle its a coles budget 1.5l water bottle but near enough remove the cap and then the little security ring that normally holds it on. Dont ask, just trust me its a pain to fish it out of the cooling system later.



cool

now fill it up and invert it into the expansion tank and it'll go glugity glugity glugity as it puts a measured 1.5l into the cooling system by changing water for air.




By this stage you should know how much goes in your cooling system and at what concentration you need to have your coolant at. so with the first 1.5-3 l of fresh water in the system add your concentrated coolant to get the dosage level you want. Of course this does assume that when you emptied the system out you had the forethought of flushing the system with distilled water until it was flowing cleanly before dumping all the distilled water out that you could.

now add more water and eventually you'll hit an equilibrium point




when that happens pull the bottle out fill it up again and make sure that the water level is higher than the next highest point in the cooling system (the heater hoses in a tdi deefer)

then start it up, give it 30 seconds or so at idle while you inspect for obvious leak then give it high idle with a blanket over the front of the grill to retard airflow.

and you'll notice this.



the concentrated coolant heated by the engine circulating up into the water bottle. (ok coke bottle if your doing it right) sometimes its got plenty of bubbles and the level will drop below that of the highest point, if it does just refill the bottle and tip it in again.

when that stops bubbling air in keep the revs on and check by hand the temperatures at the thermostat housing (dont do that on the TD5, you will loose an arm to the belt use the port on the top of the engine on the passangers side where youd expect the thermostat to be) top and bottom radiator hoses, and the heater hoses, have the heater on flat out so you can check that its flowing correctly as well. Once the engines warmed up you'll notice a fairly rapid change in the color of the water in the bottle




when it looks like its changed as much as its going to remove the bottle, cap the cooling system, cap the bottle and then move the vehicle to a dry patch of concrete to check for leaks let it idle for 5 minutes or so then take it for a drive checking the engine for leaks at the 10, 50 and 100Km marks be sure to vary your driving over the range to expose the system to the full range of operating conditions.

when you get back the system should have purged any excess coolant and now be at the right level, grab a paint pen and mark the side of the expansion tank and use that as your warm coolant level indicator, then in the morning while its cooled down mark the bottle again for the cold mark.

done and dusted, as a bonus you have about 1l of ready to use premixed coolant in a convenient bottle and if you had any contamination in the system you'll have signs of it in a ready to analyze container.

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