Lotus Elan

Draining antifreeze

PostPost by: William2 » Wed Apr 25, 2018 1:01 pm

When draining the antifreeze to replace the coolant is it essential to unscrew the drain bolt on the block behind the exhaust manifold? Also, after draining should you flush the system through using a hose pipe down the rad filler cap?
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PostPost by: nmauduit » Wed Apr 25, 2018 1:12 pm

on my car the radiator drain tap is about the lowest point, I just open the filling cap so that the coolant flows more freely at the beginning. You may get a little more out by raising the rear of the car a bit. If the goal is just to change the coolant, a quick rinse can also be done, but I usually just refill with new coolant (if a pressure rinse is intended for very dirty coolant and gummy obstructions then it's an other story, one would need to get access to as many openings as possible...)
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PostPost by: richardcox_lotus » Wed Apr 25, 2018 5:12 pm

If I’m draining the system in any case then I take the view a backward flush can’t do any harm !
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PostPost by: rgh0 » Thu Apr 26, 2018 12:06 pm

nmauduit wrote:on my car the radiator drain tap is about the lowest point, I just open the filling cap so that the coolant flows more freely at the beginning. You may get a little more out by raising the rear of the car a bit. If the goal is just to change the coolant, a quick rinse can also be done, but I usually just refill with new coolant (if a pressure rinse is intended for very dirty coolant and gummy obstructions then it's an other story, one would need to get access to as many openings as possible...)



While the radiator drain is at the lowest point coolant stays in the bottom of the blocks cooling passages unless you also open the block drain plug behind the exhaust . This is because when you drain the system you drain through the pump which is halfway up the block to the radiator drain you leave coolant in the block.. Not normally critical for a routine coolant change in a well maintained system. But if you have an old corroded block that has been poorly maintained over the last 50 years you need to fully drain and flush it to get out all the corrosion products that sit in the bottom of the block coolant jacket and are happily corroding away your block as the inhibitors in the new coolant cant get through the built up layers down there.

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PostPost by: JonB » Thu Apr 26, 2018 5:50 pm

Rohan

If the rear of the car was backed up onto a pair of ramps, might that provide enough of a tilt to drain the block's lower galleries through the radiator drain tap?

Just a thought!

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PostPost by: William2 » Fri Apr 27, 2018 8:19 am

Rohan, thanks for your reply. I think I will remove the block drain to see what comes out! Regards, William
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PostPost by: Concrete-crusher » Fri Apr 27, 2018 3:43 pm

As a matter of interest what antifreeze do people now use ? Blue or Red

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PostPost by: rgh0 » Sat Apr 28, 2018 2:24 am

JonB wrote:Rohan

If the rear of the car was backed up onto a pair of ramps, might that provide enough of a tilt to drain the block's lower galleries through the radiator drain tap?

Just a thought!

Cheers
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Raising the rear would help get any old coolant out but the sludge in the bottom of the blocks cooling jacket will probably stay there. Pulling the block drain plug and flushing through in both directions with a strong water flow will help remove any corrosion products and sludge that has built up. Treating the cooling system first with a suitable flushing product will also help.

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PostPost by: 2cams70 » Sat Apr 28, 2018 2:36 am

Beware that drain plug if it hasn't been removed for a while! Early plugs were brass which doesn't cause problems but later plugs were steel and have a nasty habit of corroding themselves solidly to the block. Whatever you do make sure you use a tight fitting spanner (socket is best). I use a 14mm socket rather than the correct 9/16" A/F as it's fractionally tighter on the nut. Especially if re-using a steel plug be sure to use some Teflon tape or pipe sealant as this protects the threads from corrosion somewhat.

I've come across cases where the corrosion has been so bad that I've had to weld a ring spanner to the plug after having rounded the flats - only then was I able to get it to budge. Once it starts turning you can cut the spanner off with an angle grinder in order to be able to turn 360 degrees. All this with the engine out of the car of course!
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PostPost by: prezoom » Sat Apr 28, 2018 3:48 pm

If doing a flush with a cleaning solution, be prepared to have your radiator repaired, if the radiator is original and radiator flushing has not been done in a very long time. BTDTHTTS. Two 2 cars, both Marsden radiators from 1964, died within weeks of each other. They both now have thicker cores.
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PostPost by: alan.barker » Tue May 01, 2018 6:12 am

If you flush the system then don't forget to flush the heater also :wink:
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PostPost by: William2 » Tue May 01, 2018 3:28 pm

When refilling the system is it worth jacking up the front of the car a bit to raise the level of the rad cap and therefore help remove air locks?
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PostPost by: billwill » Tue May 01, 2018 3:58 pm

I used to try lifting the front right wheel, on a ramp or kerb to get the rad cap higher than other parts of the cooling system, but now I have TWO caps one on the radiator and one above the thermostat.

Despite an optical illusion they are both pretty much at the same level, but the system fills better with less air trapped in the top hose if I remove both caps during filling or top up..

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Last edited by billwill on Tue May 01, 2018 4:02 pm, edited 1 time in total.
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PostPost by: JonB » Tue May 01, 2018 4:02 pm

Coolant capacity (including the heater) on a Plus 2 is 14 pints (7.9 litres; 16.8 US pints) according to the Technical Data in the Workshop manual, FWIW.
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PostPost by: alan.barker » Thu May 03, 2018 6:38 am

Bill,
i see you have 2 overflow tubes. 1 from the Thermostat housing and 1 from the Rad Cap.
How does that work, does your car have 2 Expansion Bottles :?:
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