Thread: Radiator Flush Technique Question

Originally Posted by PerthDisco

Considering PS fluid change disaster today I think I will save up for a change of the coolant reservoir tank and thermostat and top plastic fitting as part of the coolant change.

I dunno about yours, but on mine the fuel cooler hose to hard plastic line is plug-in. Just push the release buttons to un-plug it and drop it into a bucket.
It's on the drivers side right above the plastic cover at the front just outside the chassis rail. Don't even need to take the belly pan off.

When I changed coolant last year, my process was;
1. Add penrite radiator flush to existing coolant
2. Run engine at idle 10 min
3. Drain via bottom hose off radiator(belly pan off)
4. Fill with demin water (Bunnings 10l jug)
5. Run engine for 5 min at idle
6. Drain
7 refill with demin, run engine 5 min
8. Drain
9. Fill with penrite 8yr coolant concentrate mixed to correct 50/50 ratio with demin water
10. Run and bleed air out of system via bleed screw next to top radiator hose
11. Top up overflow tank as required with correct ratio mixture.

Can't use concentrate to top up as this mucks up the ratio
Cant use tap water to flush as this can leave salts and residues, demin. Water is the go.
Didn't need to replace the coolant overflow bottle, replaced the coolant outlet separately when engine is cold, no coolant in the top hose when engine is cold

The only issue I have with this is that after flushing with demin water, you will have residual water in the system so even the 50/50 mix wont be quite right. I have always made the mix more like 60/40 in these cases to accommodate. My understanding is it is not an issue to use a stronger mix (and in some cases pushes the expiry date out another 2 years) but making it weaker can be detrimental. Cant off the top of my head remember if Nulon or Penrite, but something like at 50/50 was 8 years and 60/40 was 10 years.

Originally Posted by Eric SDV6SE

When this. I changed coolant last year, my process was;
1. Add penrite radiator flush to existing coolant
2. Run engine at idle 10 min
3. Drain via bottom hose off radiator(belly pan off)
4. Fill with demin water (Bunnings 10l jug)
5. Run engine for 5 min at idle
6. Drain
7 refill with demin, run engine 5 min
8. Drain
9. Fill with penrite 8yr coolant concentrate mixed to correct 50/50 ratio with demin water
10. Run and bleed air out of system via bleed screw next to top radiator hose
11. Top up overflow tank as required with correct ratio mixture.

Can't use concentrate to top up as this mucks up the ratio
Cant use tap water to flush as this can leave salts and residues, demin. Water is the go.
Didn't need to replace the coolant overflow bottle, replaced the coolant outlet separately when engine is cold, no coolant in the top hose when engine is cold

Originally Posted by CraigE

The only issue I have with this is that after flushing with demin water, you will have residual water in the system so even the 50/50 mix wont be quite right. I have always made the mix more like 60/40 in these cases to accommodate. My understanding is it is not an issue to use a stronger mix (and in some cases pushes the expiry date out another 2 years) but making it weaker can be detrimental. Cant off the top of my head remember if Nulon or Penrite, but something like at 50/50 was 8 years and 60/40 was 10 years.

Thanks, appreciate the options and assistance and will look under today at plumbing again.

Love to know Eric how to remove shroud to access bottom radiator hose as a record for this thread.

Good to know on running Penrite flush with original coolant fluid.

The demin flushing steps then seem excessive and possible source of dilution if replacing OAT with OAT? Like trying to rinse out the last oil before an oil change? In the end the tiny amount left is overwhelmed by the new product.

Originally Posted by CraigE

The only issue I have with this is that after flushing with demin water, you will have residual water in the system so even the 50/50 mix wont be quite right. I have always made the mix more like 60/40 in these cases to accommodate. My understanding is it is not an issue to use a stronger mix (and in some cases pushes the expiry date out another 2 years) but making it weaker can be detrimental. Cant off the top of my head remember if Nulon or Penrite, but something like at 50/50 was 8 years and 60/40 was 10 years.

50% is max. 35% in normal conditions is fine.

So the water left, add the premix and you’re good to go.

Higher concentrations reduce thermal capability.

Thats why i went 50%, so any residual demin water would dilute to <50%. Old coolant came out with a slight greenish tinge, had obviously worked hard. No issues re coolant since the flush.

Btw replaced the top crossover plug with a solid brass plug, 1/8 bsp tapered thread, thanks to Dazza Td5 for the tip. Less than a 1/4 turn when undoing the oem plastic plug and it was already leaking.

Originally Posted by Eric SDV6SE

Thats why i went 50%, so any residual demin water would dilute to <50%. Old coolant came out with a slight greenish tinge, had obviously worked hard. No issues re coolant since the flush.

Btw replaced the top crossover plug with a solid brass plug, 1/8 bsp tapered thread, thanks to Dazza Td5 for the tip. Less than a 1/4 turn when undoing the oem plastic plug and it was already leaking.

Great tip. Brass 1/8 bsp tapered thread available from where?

I’m now very cautious of disturbing any 10 year old plastic fitting after Power Steering reservoir spigot broke off.

Super cheap auto. Brand is champion. Fitting costs 10 bucks, but better than losing all your coolant and overheating engine. Thanks again to Dazza for the tip.