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Marlin.45



Member Since: 20 May 2014
Location: Llangadog, Carmarthenshire
Posts: 54

Wales 2007 Defender 90 Td5 SW Baltic Blue
Coolant flush and change on the TD5 - is this right?
Our 90 does very little mileage these days but when I checked my records I realised the coolant had not been changed from new (56) 54k miles ago. Scheduled change is around 36k I believe?

Pulled the bottom rad hose off to drain down the refilled with water and vented via the bleeds on the top rad hose and the fuel cooler. Idled for 10 minutes. Ran several loads of fresh water through until the drain was clear, then added Wynns rad flush and repeat. Followed by another three flushes until clear. Drained the lot via the bottom hose then reconnected everything and poured 5 litres of OAT straight into the expansion vessel and topped up to level with rain water.

I know these engines run cool at idle (wouldn't go above the top of the blue) but after a 15 mile round trip the temp gauge settled at about 40% of span (just to the left of the centre point). Ambient was 7 Deg.C. Reading is steady and there is no sign of air in the system.

One issue though is even after a run the bottom rad hose is still pretty cold so roughly where on the temp gauge equates to the point where a good thermostat should open?

I am probably making a mountain out of nothing, which is normal for me, but to play safe I have ordered a spare stat. It's the original unit in there from new!


 2006 TD5 90 County
1961 MF35
Post #579298 20th Nov 2016 10:28pm
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Vogler



Member Since: 02 Nov 2014
Location: Brussels
Posts: 309

Belgium 2015 Defender 110 Td5 HT Chawton White
Our Td5 typically runs this cool, it looks very familiar.
Why did you use only 5 litres of OAT? According to the manual the Td5 cooling system contains 13 liters of coolant and the concentration should be 50%, 60% max. Unless you remove a plug somewhere on the side of the engine block, you will not succeed in draining it completely, there will always be three or four litres left.

I made the mistake to carefully mix 50% coolant before pouring it in, but could only add 9 to 10 litres, so concentration is too low (I measured somewhere between 30-35%. This week I'll drain 3 litres and replace them by pure coolant to'get to the 50%.


Greetings,

Joris
Post #579313 20th Nov 2016 11:05pm
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Marlin.45



Member Since: 20 May 2014
Location: Llangadog, Carmarthenshire
Posts: 54

Wales 2007 Defender 90 Td5 SW Baltic Blue
Hi Volger.

Cooling system had been flushed three times at least with clean filtered rainwater so anything that was left in there was...water. Yes the concentration may be a little low but with 5 litres of concentrate that comes to as near as dammit 40% of the total volume.

I have a coolant tester somewhere in the barn so I will check and see what that says at some point. 2006 TD5 90 County
1961 MF35
Post #579320 20th Nov 2016 11:16pm
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lightning



Member Since: 23 Apr 2009
Location: High Peak, Derbyshire
Posts: 2265

United Kingdom 
The coolant temperature has always sat at just below half on all three of my TD5's so that's normal.

When l drained my coolant l only managed to get about 8 litres of antifreeze mix back in. It's hard to get it all out.

What was the state of the coolant that you drained? Was it pink, or rusty brown? The long life stuff can still be OK after 10 years so don't worry too much about it.
Post #579608 22nd Nov 2016 8:39am
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Retroanaconda



Member Since: 04 Jan 2012
Location: Scotland
Posts: 2557

Scotland 
Perfectly normal gauge position. Bear in mind it is non-linear, gauges are designed to smooth out the normal fluctuations in engine temperature (i.e. as thermostat opens/closes) to avoid scaring people who don't know how engines work.

Bottom rad hose being cool/cold after 15 miles is normal also at this time of year. Remember the cooling system is designed to cope with 50 degree desert heat or -20 artic cold and everything in-between, so the radiator is rather over-specified for a British winter! Couple that with the heater being on and I often find that the thermostat hasn't even opened as the natural airflow over the block plus heat extraction from the heater is enough to keep the engine more or less at the required temperature, so there is very limited or no flow through the rad in these cases.
Post #579632 22nd Nov 2016 10:22am
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srod



Member Since: 20 Mar 2015
Location: Argyll
Posts: 190

Does anyone actually bother to remove the drain plug on the block, to fully drain the system? ...and if so, did you have to remove the alternator to get at it?

Decided it's time to tackle this job after a recent sleepness night spent at Glencoe, thinking over how I had absolutely no knowledge of the history and condition of the coolant in my engine, and the temp could have quite easily have got down to -10C or so.
Post #579652 22nd Nov 2016 1:34pm
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Tommo



Member Since: 19 Dec 2013
Location: Leicestershire
Posts: 830

United Kingdom 2006 Defender 90 Td5 Black LE Java Black
Yes you do need to remove the alternator. Not done it personally but it is the best way to drain the system Thumbs Up
Post #579741 22nd Nov 2016 9:32pm
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Marlin.45



Member Since: 20 May 2014
Location: Llangadog, Carmarthenshire
Posts: 54

Wales 2007 Defender 90 Td5 SW Baltic Blue
Cheers all. Coolant was still pink when I drained it but traces of rust at the last dregs.

New stat going in at the weekend anyway and I will drain then refill with the coolant I just put in there (poor planning) plus I bought another couple of litres of OAT so I may stick a litre on concentrate in to bring the concentration back up to 50% 2006 TD5 90 County
1961 MF35
Post #581447 29th Nov 2016 11:03pm
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miker



Member Since: 13 Sep 2015
Location: Surrey
Posts: 1759

United Kingdom 1999 Defender 110 Td5 CSW Rioja Red
Retroanaconda wrote:
Perfectly normal gauge position. Bear in mind it is non-linear, gauges are designed to smooth out the normal fluctuations in engine temperature (i.e. as thermostat opens/closes) to avoid scaring people who don't know how engines work.

Bottom rad hose being cool/cold after 15 miles is normal also at this time of year. Remember the cooling system is designed to cope with 50 degree desert heat or -20 artic cold and everything in-between, so the radiator is rather over-specified for a British winter! Couple that with the heater being on and I often find that the thermostat hasn't even opened as the natural airflow over the block plus heat extraction from the heater is enough to keep the engine more or less at the required temperature, so there is very limited or no flow through the rad in these cases.


Mine had a brand new stat and fresh coolant at the start of the summer. Even towing ~3t, with 9 people on bored, and a roof rack full, up and down the kent countryside in the hot week in august, I still didn't notice any warmth in the lower rad hose! Temp guage rock solid at its "just below middle" point too.
Post #581460 29th Nov 2016 11:37pm
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Marlin.45



Member Since: 20 May 2014
Location: Llangadog, Carmarthenshire
Posts: 54

Wales 2007 Defender 90 Td5 SW Baltic Blue
Cheers Miker,

I have so many jobs on the 'honey do' list at the moment I may chuck the stat in a box for a while and get on with other priorities then Laughing 2006 TD5 90 County
1961 MF35
Post #581628 30th Nov 2016 2:50pm
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