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Triumph TR6 - Draining the radiator and replacing the antifreeze

Just had a burst hose this past Sunday, the end of a beautiful ride...Now I have to change the burst hose and refill the radiator with coolant fluid.
I have never done it so what is the procedure, I have heard two different methods from two Triumph mechanics.
How much coolant do it put in, and is there a step by step method I should follow to do this properly.
Thank you in advance for your help !
L. Towel

I usually don't worry about the amount of coolant to put in, but I'd buy at least a gallon of undiluted, probably 2. They do make a lot of pre-diluted containers now, they cost a bit more though.

I'm a bit cheap, and have an extra container to mix the full strength stuff 50/50 with water. I just pour half of the antifreeze into the other container and fill them both up with water, then mark them 50/50 with a magic marker. You could use distilled water if your local water has a lot of minerals, but that would probably make the prediluted stuff about the same price.

There should be a petcock on the bottom tank of the radiator to drain it into a pan. Do that, close the petcock, then replace your hose. You may have to cut the old one off of the fittings or force an old screwdriver around the seal, as it may be stuck pretty hard. Determine the best side to put the screws on the clamps for accessability and possible interference with items nearby. Put the hose clamps on the new hose, farther in than where they will be later. A bit of antifreeze is kind of slippery to help slip the new hose on. After the hose is in place, position the clamps for best sealing and access.

Pour as much mix as you can fit in the filler neck. Start the car and let it get to operating temp so the thermostat opens and lets out air bubbles. The level will probably drop some, so fill 'er up. Put the cap back on drive around the block, and check for leaks. Don't burn yourself. Check the level and look for leaks before you start her up the next few drives, and all should be fine. You could open the heater valve if you like to get that circulated and checked before winter, but if it's as hot there as it is here, I'd wait a month or so to do that.


I agree with Tom, but thought I would add that if your car is a later one then you won't have any way to drain the radiator other than removing the bottom hose - the tap was discontinued at some point, from what I understand. My '75 certainly doesn't have one.

Oh, and if you have incredibly small fingers or are double jointed, you could also remove the drain plug on the rear of the engine block, just above the starter - I removed mine this spring expecting a gush of water, and got nothing at all - took me half an hour of scraping with an old coat hanger to get the crud out. I did it with the manifolds off and it was still quite awkward, so I dread to think how you would do it with everything together!


All advise above looks good. The only thing I do differently is to use distilled water with the anti-freeze. That way no minerals are present and can't block up the radiator core. A small added expense initially, but saves an expensive radiator later.

I found the same thing as Alistair - the drain tap in the block is usually plugged up. On the parts car I stripped, the drain plug had been missing for a long time and it still didn't leak even with the system up to temp/pressure! Took quite a bit of digging around to get it open.

Tom Sotomayor

Always wondered if we could manufactor something for the 75/76 years that would simplify drainage..p[erhaps a stopcock/pipe that would be inserted into the lower hose like a t junction? Has anyone ever tried something like this...i personally hate wearing coolant and disconnecting hoses...sure fire way to do just that

Bob Craske

Bob-The next time you remove the radiator (and there always is a next time)take it to a radiator shop and have the petcock installed that the factory deleted to save a few cents.
Berry Price
BTP Price

Cool ideas! Last coolant change I wanted to give the system (and heater core) a real good flush. Being to lazy to try and get the block drain plug out I bought a cheap T connector at my local auto store to put in the old heater hose (I changed all the hoses too). You connect the garden hose to this T, leave the heater valve wide open and can run lotsa water thru to do a good clean. (I ended up collecting a lot more mixture for hazardous waste recycling than a normal change).
Then I closed everything up, got it full with just water then drained the rad keeping track of how much water came out. I checked the total engine/rad capacity and found it was almost bang on 50% that came out of the rad. So then I added straight coolant to top up. Checked the coolant strength and it was perfect.
I'd prefer to use distilled water, but I do feel assured that I got a lot of little bits out.
Ian Marlatt

Bob, I did just that last winter when I put an electric fan on my car. I welded a 1/4" pipe fitting onto the back side of the lower rad pipe, got a 1/4" drain cock from Princess Auto for $2. Works like a charm, no more mess all over my garage floor when draining the rad.

Darn Brits and cutting corners.
My '71 has a tap at the rad and on the block above the starter.
Rick Crawford

So that's what that drain cock is for on the block. Thanks Rick!!
Doug Baker

This thread was discussed between 14/08/2007 and 19/08/2007

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