Thermostat TD5

**Tins** · 11th October 2025, 03:51 PM

Originally Posted by discorevy

2 of the most common reasons for overheating on a highish kilometer TD5:

Crumbled plastic head dowels

Viscous fan failure.

I know the first one seems a bit doom and gloom, but it was ( most have gone to steel now, with no further issue ) common.

Had the first one. 150,000 ks ago done 360 now. . Yep, head moved. The fan is on my list. Thing is, this was reasonably sudden, and it happened after silly me didn't tighten the cap properly ( right arm doesn't work properly atm ) Car has been rock solid prior.

**Tins** · 11th October 2025, 03:52 PM

Originally Posted by TonyC

John, surely this is not news to you!

No, not at all. Just surprising the range of temps the gauge refuses to acknowledge.

**Captain_Rightfoot** · 12th October 2025, 09:15 AM

Originally Posted by Tins

No, not at all. Just surprising the range of temps the gauge refuses to acknowledge.

I was watching my temp. Gauge is the same from like 80 something to 110.

**Tins** · 12th October 2025, 09:21 AM

Originally Posted by Captain_Rightfoot

I was watching my temp. Gauge is the same from like 80 something to 110.

Yep. 77 to 110° in my case Then the gauge starts to move and the engine de-rates. Mine cools quickly as well, which suggests to ma an air lock or a moving restriction. Something like I've seen before when people have knocked welch plugs in rather than removing them.

**Captain_Rightfoot** · 12th October 2025, 11:52 AM

Originally Posted by Tins

Yep. 77 to 110° in my case Then the gauge starts to move and the engine de-rates. Mine cools quickly as well, which suggests to ma an air lock or a moving restriction. Something like I've seen before when people have knocked welch plugs in rather than removing them.

Interesting! Fortunately never quite got to derating.

I changed the coolant before the trip. But was just a flush. With the TD5Spy I've definitely got more awareness, but I have run the old nanocom in the past and not seen anything like that temp. I seem to remember last time I was surprised when it got to 95 going up the toowoomba range.

I also don't recall hearing the fan.

**Tins** · 12th October 2025, 01:18 PM

Originally Posted by Captain_Rightfoot

Interesting! Fortunately never quite got to derating.

I changed the coolant before the trip. But was just a flush. With the TD5Spy I've definitely got more awareness, but I have run the old nanocom in the past and not seen anything like that temp. I seem to remember last time I was surprised when it got to 95 going up the toowoomba range.

I also don't recall hearing the fan.

Mine has been fine, until now. It will maintain 82° for ages and then rocket up. And then come down just as quickly. I know it's not the sensor because the car does get hot, visibly. Thing to do is pull the rad, change the thermostat, and bleed it properly to see what happens. I don't believe it's the HG, but it probably soon will be......
Wish both my arms worked..

**Captain_Rightfoot** · 12th October 2025, 08:35 PM

I discovered my clutch fan tonight.. despite "feeling good" when spun, the shaft that the bimetallic strip operates had seized, or the bimetallic strip was too rusty.. or something. Either way when hit with heat it wasn't turning the shaft and locking up. High temps explained!

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