Draining antifreeze

There are two drains - one at the bottom of the radiator and one on the side of the block near the dip stick hole.

The radiator drain opens but the one off the block is really stuck. I’m worried about making matters worse by forcing it.

So I warmed up the engine slightly and then opened the radiator port and managed to drain out about 3 gallons. Trouble is that according to Bentley total capacity is about 5 gals. I did have the heater set to hot.

Am I missing something?

67 e type s1 2+2

They can be a real bear, and almost always are plugged by deposits.

Getting it out of the block, in its entirety, is a better option.

Is it simply impossible to correctly drain the coolant without getting the block drain to open?

Failing getting the petcock out, remove the lower hose on the pump, and jack the rear up.

I’d take the opportunity to remove the t-stat, and power flush the cooling jacket, and the radiator.

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what Paul W said…or race ramps on rear,
or…drain what you can, fill with plain water, close, run…let cool, do it again add a system flush product-follow manufacturer directions, , …, then again…and once more…until only clear water. Drain, refill m, say 60 anti fr to-40 distilled water, to allow enuf anti freeze mix for the water still in the system. Run, let cool and Finally check with an anti -freeze tester…(cheap at stores) you want -34. which .tells you that you have 50-50, Nick

Removing the block drain is arguably the most important thing. If you’re doing a full flush you want to get out as much rust deposit as possible and most of it’s in the block.

What you might want to do is to take this opportunity to unbolt the thing, remove the cotter pin and clean the taper on the petcock. It’s a very crude valve and debris gets in and cruds it up. You can force it to turn with some penetrating oil and an extension tube over the handle, but doing do with a lot of crud in there might score it worse.

Just have a long funnel handy to route it into a pan if you decide to unbolt it. I’d also let it stew in penetrating oil before attempting to unscrew it.

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If you take the drain tap out f the block, they are really simple to take apart, clean up and lap back into perfect working condition using fine grinding paste.

Very, very fine. I ruined my original one using stuff from the FLAPS. Unless it’s already scored I’d be inclined to just use something like Mothers, then grease it and call it a day if it holds air at 15psi.

I have found that you really need to build up some pressure in cooling system to flush out debris.
One option is a tee fitting that a garden hose attaches to, another is a expanding rubber bladder that also attaches to garden hose. One just has to me careful not to build up too much pressure. I have used the bladder method for years. I keep my cooling systems clean and coolant fresh but still had a water pump full of rust when I just removed it to install new one. I had given up on the block drain valve and just use a threaded plug .

I ruined one with valve grinding compound as well, couldn’t get it to stop dripping. Fixed it permanently with silicone sealer. Now only I know it is just a funny looking block drain plug.

To lap in that taper, one should use nothing coaser than jeweler’s rouge.

I did the same thing on the one in my '68, the last one I did I used auto polish (fine rouge), put it in the drill press and worked a charm.

I used fine valve grinding compound, I believe on the suggestion of Ray L and it worked like a charm, no problems at all! Don’t try this if you have zero mechanical acumen though, which I would have thought anyone on this list would be astute in such matters.

Apologies to Ray L if it wasn’t him.

How’d you mount the part in a drill press? I assume the handle and you held the body?

In this day and age, I suspect jewelers rouge will be easier to source than Clover fine grinding grease: that said, either work fine.

I had the water pump replaced about three years ago - so this should have in theory done a pretty good job of cleaning out all the crud from both block and radiator.

My take away from all this is that I’ll ‘tip’ the car up back to front next time I drain the antifreeze in order to pull out more because I’m terrified about either breaking the block tap or having to somehow tap in a new one…

This go around I pulled out almost exactly 3 gallons or fluid. This will allow me to determine exactly what impact the tilt will have…


A BSPT plug is pretty cheap. It actually seems to do a much better flush than the itty bitty spout does because the coolant comes rushing out and drags all the icky along with it. You just have to be prepared with an appropriate receptacle to catch it all.

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Hi Erica,
That’s it, put the end of the handle in the chuck and held the body. Doesn’t sound very safe does it, a hand drill may be a better idea.

Just leave the tap closed and unscrew it from the block. Let the block drain and be happy. I wouldn’t mess with lapping the valve, because a stuck valve that’s closed is better than a botched valve that leaks. Jaguar replaced the tap with a hex plug in 1969, and they knew their business.


That’s what I did.

Really tempted to put a nice ball valve in from the hardware store, but I think I’ll leave well enough alone.