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Draining cooling system


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I think it about time to drain the cooling system & put in some fresh anti freeze. The block drain plug is seized up closed so I can only drain by removing the bottom rad hose. What are peoples methods to drain & flush the system without getting any air locks?

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Hi Monty,

It should be possible to unwind the block drain cock and replace with a decent one.

Clear the local internals with a wire coat hanger.

 

I normally top up the system (before draining) with something like RadFlush   and run the engine for a number of hours.

Then drain and rinse out with a hose in both directions.

Then fill with 50%  Bluecol etc

 

Roger    

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I jack the front of the car up as high as I dare to fill the rad then lower it to the ground before running the engine with the cap removed. Once thermostat opens run it for another couple of minutes prior to topping up and fitting the cap. I then take it for a short run and let it cool before checking the level and topping it up again. 
As Roger said unscrew the block drain tap and sort it out on the bench. A bit of poking and maybe some running with a flushing agent generally gets some flow from the block drain port. If not either refit the tap and forget about it or if you’re bored and wallowing in cash strip the engine and get the block tanked. 

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38 minutes ago, RogerH said:

Hi Monty,

It should be possible to unwind the block drain cock and replace with a decent one.

Clear the local internals with a wire coat hanger.

 

I normally top up the system (before draining) with something like RadFlush   and run the engine for a number of hours.

Then drain and rinse out with a hose in both directions.

Then fill with 50%  Bluecol etc

 

Roger    

Hi Roger, As the block drain cock has been like it for years I am loath to try & force it in case of breakage in the block plus it is awkward to get at with manifolds etc. Definitely Radflush & Bluecol though. No sign of overheating for years even on a track day yesterday! I was just worried about the airlock situation that I once had in the past with lack of real heat from the heater.

 

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"plus it is awkward to get at with manifolds etc."

Monty, it is not as tempting as you think to leave it. It is extreeeeemely doubtful that without adequate access you will...

1) Remove the tap from the block ( with access I have stripped "Titanic" grade corrosion blocks ok) without the tap either stripping or shearing. It should be a BSP fitting originally with a taper into the block, it only takes about 1 1/2 turns for it to come loose. BUT you do have to be able to see it and room to turn a large wrench to make it easy.

2) with the manifolds off and tap removed you can poke out the hole which is at the lowest part of the engine block and so is full of rust, gunge and dead mice. That's why your (and everybodies) No 4 cylinder is the hottest on the engine, worth the opportunity to clean out and help restore at least some flow to the area and help your engine cool better in summer. I often resort to a small drill bit in the Makita and drill out the hole (they are that blocked, but carefully, you don't want to break the bit inside against the rust. The liners are at their thickest at that point so no chance of damage there.

I reckon 45 mins to remove the carbs and manifold and lay on the easiest part of engine or bodywork. Then a further 15 mins to pull the exhaust manifold across and you should be in for the block drain tap. Well worth it. 

The block air lock is easier to avaoid with a working block drain, you can keep bleeding it through from there rather than the bottom of the rad.

Mick Richards

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Are you prepared for another opinion?

In my opinion all worries about an airlocks are needless,

you can’t compare an engine cooling system with a „toy“  house heating system.

A car’s water pump is a M-O-N-S-T-E-R and blows all air out and keeps it in the flow.

I regard nothing about air in the system - I just take care to keep enough of it in there!

You can poke the drain hole by the 4 th cylinder free to drain it, like I did for dismantling the liners out of my engine some years ago.

Pulling the liners I anyway found coolant remaining there and the gap between the liners and engine housing filled up with rust sediment solid like concrete.

In my opinion poking the hole free causes not very much.

Finally: if you had no coolant problems - what do you worry?

Ciao, Marco

Edited by Z320
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2 hours ago, Z320 said:

Are you prepared for another opinion?

In my opinion all worries about an airlocks are needless,

you can’t compare an engine cooling system with a „toy“  house heating system.

A car’s water pump is a M-O-N-S-T-E-R and blows all air out and keeps it in the flow.

I regard nothing about air in the system - I just take care to keep enough of it in there!

You can poke the drain hole by the 4 th cylinder free to drain it, like I did for dismantling the liners out of my engine some years ago.

Pulling the liners I anyway found coolant remaining there and the gap between the liners and engine housing filled up with rust sediment solid like concrete.

In my opinion poking the hole free causes not very much.

Finally: if you had no coolant problems - what do you worry?

Ciao, Marco

Hi Marco,

Cooling system has always been good, electric fan kicks in when it should etc but have not changed the anti freeze for some while so thought I would just drain, flush & refill. Did not want a major dismantling session if it could be avoided so will drain the rad, disconnect hoses & see what comes out. Last time I did it, some years ago, all I got out was pale blue anti freeze/water & no muck at all! A waste of time really but it is old anti freeze in there so…?
Glad I bought one of your locking caps Marco with the price & shortages of fuel these days!
Cheers.

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I don't think that Radflush would be able to shift the accumulated solid muck by the bottom of number 4 liner.

I agree with Mick that the drain cock should be removed and either made to work or replaced.  Back in 1966, we removed the drain cock from my brother's TR3 and found that not only was there an incredible amount of solid muck inside the block, but the drain cock itself was in the OPEN position, but not leaking because of the muck both inside it and the wall of muck inside the block.

Just make sure that any replacement cock has the correct thread, seals to the block and doesn't weep.  It's worthwhile lapping the moving parts together with a very fine paste (even Brasso) in order to ensure that it doesn't widdle under pressure!

I find it odd that some of these cocks have the handle in line with the direction of flow when closed, others have the handle at right angles.  I have examples of both in my collection of parts.

Ian Cornish

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1 hour ago, monty said:

Hi Marco,

Cooling system has always been good, electric fan kicks in when it should etc but have not changed the anti freeze for some while so thought I would just drain, flush & refill. Did not want a major dismantling session if it could be avoided so will drain the rad, disconnect hoses & see what comes out. Last time I did it, some years ago, all I got out was pale blue anti freeze/water & no muck at all! A waste of time really but it is old anti freeze in there so…?
Glad I bought one of your locking caps Marco with the price & shortages of fuel these days!
Cheers.

So don't worry about the cooling system, this is no rocket technic.

Great to hear you are still pleased with my fuel cap lock.

Next I finish work at my office and will go to the post office with 8 (!) parcels going out to the UK.

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4 hours ago, ianc said:

It's worthwhile lapping the moving parts together with a very fine paste (even Brasso) in order to ensure that it doesn't widdle under pressure!

I find it odd that some of these cocks have the handle in line with the direction of flow when closed, others have the handle at right angles.  I have examples of both in my collection of parts.

 

I think I made too good a job of lapping mine; on mine, the handle is pointing backwards parallel with the side of the block when closed, and at right-angles when open. On one of the first trips after the 6-year restoration, I had to stop a bit quickly, and the inertia of the handle opened the tap! I promptly wired it shut, and it stayed that way until the next coolant change, by which time it had got a bit stiff to turn.

Pete

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Hi there,

btw the thread of the drain tap indeed should be BSP (1/4"-19), because it is a fluid valve!

On my TR4A it was ripped off but the hole not leaking (as Ian reports), on my spare part enginge the tap was 1/4" BSP and off with only 1 turn.

Because the thread surprisingly on both engine blocks is 1/2"-20 UNF, this is why BSP tapered "fits" but allows only 1-1.5 turns.

I fitted a ball valve 1/4" BSP

8NGf9Ye4pv-fZg79QEwrXwJVz4SrWpoZf2rOCxLw

To do this I used an DIY adapter 1/4" BSP x 1/2" UNF

R8k1kTRflv7tmo2TkToupgZYuLI9hhiIX0Fr01mw

I already posted this here at the forum - but nobody believed me.....

Ciao, Marco

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40 minutes ago, Z320 said:

Hi there,

btw the thread of the drain tap indeed should be BSP (1/4"-19), because it is a fluid valve!

On my TR4A it was ripped off but the hole not leaking (as Ian reports), on my spare part enginge the tap was 1/4" BSP and off with only 1 turn.

Because the thread surprisingly on both engine blocks is 1/2"-20 UNF, this is why BSP tapered "fits" but allows only 1-1.5 turns.

I fitted a ball valve 1/4" BSP

8NGf9Ye4pv-fZg79QEwrXwJVz4SrWpoZf2rOCxLw

To do this I used an DIY adapter 1/4" BSP x 1/2" UNF

R8k1kTRflv7tmo2TkToupgZYuLI9hhiIX0Fr01mw

I already posted this here at the forum - but nobody believed me.....

Ciao, Marco

My memory says the cylinder block drain tap position is unf threaded and the radiator drain tap position is BSP threaded.  

That is why there are two drain taps listed in the original parts book.  
 

Edited by BlueTR3A-5EKT
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15 hours ago, Z320 said:

In my opinion all worries about an airlocks are needless,

+1 on that... been driving a TR for 30+ years from alpine winters to tropical summer & never had an airlock.

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A  while ago I had a leaking heater matrix so removed it and started to take it apart to see if I could fix it (don't ever bother to do this as you can't fix them - just buy another). Anyway when I removed the 2 end boxes I discovered they were 1/2 full of sediment. So I would have thought that one of the things to do is to disconnect the 2 pipes that feed the heater in the engine bay at the bulkhead and give the heater matrix a good flush out as well as the engine and radiator. The radiator can also be flushed separately. The design of the heater box is poor for water flow and with the multitude of soldered joints is a leak waiting to happen. I did look at making a better design with a copper tube design similar to the uprated classic jaguar heaters but didn't get very far. Just got a new core matrix and put it in the car.

Keith

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On 10/8/2021 at 1:37 PM, Drewmotty said:

I jack the front of the car up as high as I dare to fill the rad then lower it to the ground before running the engine with the cap removed. Once thermostat opens run it for another couple of minutes prior to topping up and fitting the cap. I then take it for a short run and let it cool before checking the level and topping it up again. 
As Roger said unscrew the block drain tap and sort it out on the bench. A bit of poking and maybe some running with a flushing agent generally gets some flow from the block drain port. If not either refit the tap and forget about it or if you’re bored and wallowing in cash strip the engine and get the block tanked. 

Hi Drewmotty, assuming the tap is forgotten what is your system of trying to flush the block?

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