Coolant leak saga!

5.0 V10 50v biturbo - 571 bhp
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Ooonst
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Coolant leak saga!

Post by Ooonst » Sat Jul 26, 2025 6:22 am

Gidday!

Thought I'd share my fun with my Coolant problems. I had a coolant leak coming from what I thought was the expansion tank so managed to source a new one and replaced it. Rather hard getting the tube on the bottom (part 18) of it requiring removing the charge pipe and air filter on that drivers (Right hand) side.

Once I'd completed that I located another coolant system problem with the plastics lines that go under the same side wheel arch into the main reservoir (Yellow number 3 Part in the diagram
Coolant Problems 1.png
). So I replaced one of these with some hose and clamps, chuffed that I had plugged all the problems with the system. I did not bleed the coolant system properly (!!!) and proceeded to take it for long relaxed drive. I think we did about 90km. Just as I was nearing home a radiator hose blew off and the I dumped majority of the coolant on the ground and the engine temp started heading in the wrong direction.

Having today fixed that radiator connection (see attached pic ) with another hose clamp, I noted that the smaller coolant (return?) line that goes into the same junction on the top corner of the radiator (red circle in the diagram and bottom right of photo) is buggered. There is literally not much plastic to clamp a hose clamp back on to and I guess this is actually part of the radiator side ?? Is it possible to get a replacement for just this part or do I need to get a whole new (very expensive!) radiator just to resolve this small piece of broken plastic on the corner?

As a side note, now that I thought I had resolved all the coolant leaks, I tried topping up the coolant and running the engine for about 15m with the expansion tank lid off, the fans in the HVAC system both set to "Hi" temp and lowish fan speed (3-5). All seemed to go well with no leaks (yet) and stable 90 degree coolant temp. Then I drove it across the road to park it on a different angle to see if I could move the remaining air bubbles around and vent them out the Expansion tank. At this point I was still not able to get any heat out of the HVAC system inside the cabin. I noted that the coolant level in the main reservoir was bellow minimum. I stuck probably another 2-3 litres of pre-mixed G12 coolant in there and then about 5 minutes later Steam started coming from some unknown location lower down in the engine. I guess I still have a coolant leak!

Another question - Doe's anyone know where the "coolant" thermostat(s) are located and associated Part numbers? I'm thinking I might need a new one of these. I found 4F0115201B but this seems to be the Oil thermostat/thermostat housing - not what I'm looking for.

Thanks in advance!!
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Coolant Problems 2.jpg

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Ooonst
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Re: Coolant leak saga!

Post by Ooonst » Sat Jul 26, 2025 6:43 am

To partly answer my own question about the Thermostats it looks like it has 3:
Coolant Problems 3.png
Coolant Problems 4.png
Coolant Problems 5.png

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Ooonst
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Re: Coolant leak saga!

Post by Ooonst » Thu Jul 31, 2025 8:32 am

Looks like I'm getting a new radiator because of that little plastic nozzle in the top corner of the radiator. :audibash:

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Ooonst
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Re: Coolant leak saga!

Post by Ooonst » Thu Jul 31, 2025 8:35 am

Anyone know if there are any after market, all metal solutions to the <beep> plastic sided radiator ? I've been hunting around and not found anything yet.

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Re: Coolant leak saga!

Post by Ooonst » Mon Aug 25, 2025 10:39 am

Annnnd a new Thermostat. Hard to find?? Bought one from Spareto for far too much money before realising that ECS had one for much, much less https://www.ecstuning.com/b-genuine-vol ... 7k121115c/

Jim Haseltine
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Re: Coolant leak saga!

Post by Jim Haseltine » Tue Aug 26, 2025 8:39 am

Except - the linked part doesn't fit a BUH engine.

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