Citroen C3 1.1 - thermostat housing body bolts torque ?

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longgo
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Citroen C3 1.1 - thermostat housing body bolts torque ?

Post by longgo »

Hi fellas!

In some near point (end of the week perhaps) , I have to replace leaking thermostat housing of Citroen C3-mkII 1.1 engine. I think is TU1A engine. About 60-ish horses and one monkey riding the beast.

The body look like that:
thermostat-coolant-q.jpg
and it is made from some aluminum alloy. The thermostat body is plastic.

My question is about the bolts tightening torque. In the replacing manual inside the Citroen database it only show the order of replacement.
In some other manual related to C2/C3 found that one:
thermostat-coolant-p.jpg
thermostat-coolant-l.jpg
Unfortunately my small "regular" torque wrench start from 10Nm up to 25Nm and my electronic adapter I think is from 5Nm up to 200Nm (if I can trust it..)
So, is that 8Nm true? Even the plastic valve cover torque is about 10-13Nm.. Sure, some lock compound will be applied but anyhow that seems quite light tightening..

Thank you in advance for your contribution on the topic
ozvtr
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Re: Citroen C3 1.1 - thermostat housing body bolts torque ?

Post by ozvtr »

There are two types of thermostat housings Plastic and aluminium. Then there is the thermostat outlet, that's always plastic.
The plastic housings have rubber gaskets embedded in the mating face of the housing. The aluminium housings need RTV to seal them.
You will need to ensure the mating surface of the cylinder head and aluminium thermostat housing are flat. Use a thin bead of RTV on on the thermostat housing face only.
8Nm is 70 in/lbs. If I recall, the bolts are only M5, over torquing them may damage the threads in the cylinder head
Engineering spec for M5 bolt is 8Nm.
I don't know what you mean by "the plastic valve cover". What plastic valve cover are you talking about?
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longgo
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Re: Citroen C3 1.1 - thermostat housing body bolts torque ?

Post by longgo »

In the first post I mentioned that the housing body is made from Aluminum and I doubt a bit that the bolts are M5 because the holes for them in the body are 8.3mm in diameter.
They are just perfect for M8 to pass through, and if indeed they are M8 - then 8Nm should be quite low in my opinion..
Together with that part in the package arrive some soft polymer gasket for the body. No RTV or silicone should be applied in that case.
You`re right, the thermostat outlet is plastic with already rubber O-seal mounted. It screws are M6 in size and because is plastic make sense to be tighten about 7-8Nm..

As for the "plastic valve cover" I mean exactly valve covers.. (valve, camshaft, on top of the engine head..) Some models as Citroen C5-mk2 2.0 engine, or VW Passat 1.9TDI , Fiat Punto 1.2 or.. (put your model here) have M6 or even M8 bots to hold that cover and there is 10-15Nm of torque to be applied. That`s why I was wondering if the big aluminum housing have holes (and perhaps bolts) M8 how much will be the torque?
For sure the gasket should be not overtight ... so shall I use the average momentum for M8 and then reduce it with 20% and go ahead... :o
ozvtr
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Re: Citroen C3 1.1 - thermostat housing body bolts torque ?

Post by ozvtr »

longgo wrote: 03 Jun 2024, 21:27 As for the "plastic valve cover" I mean exactly valve covers.. (valve, camshaft, on top of the engine head..) Some models as Citroen C5-mk2 2.0 engine, or VW Passat 1.9TDI , Fiat Punto 1.2 or.. (put your model here)
I'm sorry. I was laboring under the misapprehension that you were talking about PSAs 1.1 TU1 engine as installed in the Mk2 Citroen C3. But apparently you are not. My bad. :lol:
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longgo
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Re: Citroen C3 1.1 - thermostat housing body bolts torque ?

Post by longgo »

You where right! The bolts are indeed 6mm...
water-temp-sensor.JPG
Then it make sense this 8Nm quoted torque , but for me it make nonsense why the holes in the casting are made 8.3mm :shock:

Thanks for the participation!
ozvtr
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Re: Citroen C3 1.1 - thermostat housing body bolts torque ?

Post by ozvtr »

Well, I wasn't exactly right, so I wont take any credit. :lol: But I did remember that they weren't very large diameter bolts.
I removed an aluminium thermostat housing from a TU3 cylinder head to get some machining done to the head. All of the resources that I could find said the housing is sealed back onto the head with RTV. So that's what I did. Again, from my references there was no gasket (the same as your diagram). I used the Citroen's mechanics hand book and doc backup for the torques (what ever they might have said-cant remember). And that housing has not leaked.
I am certainly NOT saying DON'T use the gasket. It's just that you cant buy a gasket without buying the kit, as you did.
As the table says there are 8 of those bolts clamping the housing and I guess they (PSA) are going for large(ish) numbers of bolts at a low(ish) clamping force rather than a few bolts at high clamping force?
Just for the kiddies playing at home, the thermostat housing has two separate chambers. Of course there is the cylinder head coolant outlet chamber. But also A chamber that covers the end of cam shaft and the camshaft retaining clamp. So the housing has to seal against oil and coolant.