Thermostat opening temperature

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alviesinger42
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Thermostat opening temperature

Post by alviesinger42 »

Can someone confirm the correct thermostat opening temperature for my six please?

I have a 1986 UK 635csi, I think the part number I need is 11531710953. When I search this on eBay I find many units that claim to be equivalent to this part number, however some are 71 degC and some are 80 degC. I am fairly confident I want 80, but would like to be sure.

I am about to change my water pump and thought I would add a new stat while the coolant was out.

Cheers

Richard
1986 635csi auto
GRNSHRK
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Re: Thermostat opening temperature

Post by GRNSHRK »

Richard, fairly certain that 80 degrees is stock, but there are options out there, I've seen both 75 and 71 degrees offered, maybe aftermarket only :-k

FWIW, I went with 75 degrees a while back in my series I and unless I'm sitting in traffic, I'm not even sure that I get up to full operating temp :-?

:mrgreen:
:mrgreen:
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alviesinger42
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Re: Thermostat opening temperature

Post by alviesinger42 »

Thanks Pal,

I will go with the 80 degC in that case.

Cheers

Richard
1986 635csi auto
alviesinger42
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Re: Thermostat opening temperature

Post by alviesinger42 »

For my future reference, is there an easy way to drain the coolant from the engine side of the thermostat ?

I drained the coolant through the bottom radiator hose, but still got wet when I took the water pump off.

Also, are there any tips for getting the coolant back in / bleeding air etc.


Cheers

Richard
1986 635csi auto
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Hefeweizen
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Re: Thermostat opening temperature

Post by Hefeweizen »

Whenever I want to drain my system, I open up the bleeder screw on the bottom at the radiator and use compressed air to blow out the system through the hose at the overflow tank. Worked pretty well when I changed the head gasket last.
Rainer
03 330Xi (DD)
85 635CSi (RIP 3 May 19)
80 633CSi (Red Euro, Project)

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Brucey
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Re: Thermostat opening temperature

Post by Brucey »

there are two different types of thermostat shape, depending on whether you have an early or late tstat housing. If you get the wrong tstat (and the wrong one looks like it fits BTW), that would be a bad thing.

In the UK an 80C tstat is correct. In warmer climes some folk run a lower temperature one but with open loop fuelling, the engine management will interpret that as being an engine that isn't warmed up fully, and throw fuel into the engine like it is going out of fashion. I'd stick with 80C if you are going to use the car normally.

cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
alviesinger42
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Re: Thermostat opening temperature

Post by alviesinger42 »

Thanks guys,

Any tips on refilling the coolant ?

I have filtered what came out, but can't quite get it all back in. I am left with about 1.5 litres.

I made sure my heater control was at hot before I started. I have got quite a lot of air out of the thermostat housing bleed screw, but now just fluid.
The top radiator hose doesn't feel like there is anything in it yet.

Cheers

Richard
1986 635csi auto
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Brucey
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Re: Thermostat opening temperature

Post by Brucey »

the cooling circuit, if full to certain point, self-bleeds in use. You won't (easily) get all the coolant back in right away.

Preferably with the car parked with the nose slightly uphill, run the engine up with the cap off the header tank, until the tstat opens. Add more coolant if required.

During this process, use the bleed screw on the tstat housing to make sure that there is at least coolant round the tstat itself. Whilst it isn't too hot to handle, squeeze the top hose from time to time, in order to encourage air to be pushed out of the system

Important: ****Check that the bleed hose is flowing plenty of coolant**** - if this hose is blocked the system will never bleed out. The bleed hose runs from the top of the radiator to the header tank. This should have coolant flowing through it all the time the tstat is open. If you have not checked it is free from obstruction yet, do so.

Top up the coolant, put the cap on the header tank, and go for a drive. Use the heater, drive normally and use a normal range of engine rpms. Check that the coolant level is OK. If necessary add more coolant once the system has cooled down.

hth

cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
alviesinger42
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Re: Thermostat opening temperature

Post by alviesinger42 »

Thanks Brucey.
1986 635csi auto
Ronnie Wilson
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Re: Thermostat opening temperature

Post by Ronnie Wilson »

Hi,
i have a uk car and have just changed my thermostat. The temperature is marked on the old one. The new one also has 80'c on it. Just in the process of changing my standard coolant to evans waterless coolant. Have drained the system and put in the prep fluid first.
Will run this for sometime to absorb leftover water then drain this out ,firstly filtering it back into its container.
The prep fluid and waterless coolant are reusable if you filter out any contaminated particles.
Have changed all eight or nine rubber hoses and Will also fit new header tank and water pump. Will report back if I notice any performance differences.
Ronnie
Liverpool uk.
1986 635csi.
Bronze Beige Metallic.
alviesinger42
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Re: Thermostat opening temperature

Post by alviesinger42 »

Hi Folks,

Having a bit of a nightmare with getting the coolant back into the engine.

I thought I had most of it back in, ran the engine with the reservoir cap off. Periodically opened the bleed screw and squeezed the top and bottom hoses. I found that the level in the reservoir began to creep up as the engine warmed, so I put the engine off and syphoned a wee drop out. Engine on again and the same thing happened.
I got as far as the gauge showing just above normal operating temp and the coolant level rose slightly in the tank again. However this time when I shut the engine off the fluid gushed out of the reservoir covering my engine.

I noted that the top hose was hot prior to this, but the bottom hose was only warm. I was getting plenty of heat from the interior heating. But I still had at least 2 litres less fluid in the system than before I drained it.

The car was running a driving fine before I changed the water pump, I ended up not changing the stat as I couldn't source the right one.

Please help, I now cannot get my car back in the garage without running the engine.
1986 635csi auto
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hornhospital
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Re: Thermostat opening temperature

Post by hornhospital »

Fill and close the system. If the cap is good you should lose no coolant during warm up.
Run the car until it reaches operating temperature. Don't let it go beyond mid-gauge.
Shut the engine off and allow it to cool.
Open the system and top it off. I'll guarantee it will be low if you've actually filled it with less than what came out.
Close the system and repeat. By the second cycle it should be full.
Ken Kanne
'84 633CSi "Sylvia"; '85 635CSi "Katja";'85 325e "Hazel Ann"; '95 M3 "Ashlyn"
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Brucey
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Re: Thermostat opening temperature

Post by Brucey »

is there any assurance that the old 'stat is any good? If it does not open then you will get exactly the symptoms you describe.

If there is any doubt whatsoever about the 'stat, remove it and test it. It should open fully and briskly if immersed in boiling water.

The rising level in the header tank means there is air trapped in the system; the air gets hot and expands, pushing coolant into the bottle. If the stat does not open (as suggested by the hose temperatures) you won't get any self-bleeding effect.

NB the system definitely won't bleed properly (even when the stat is open) unless the bleed hose is flowing coolant. I cannot emphasise that it is imperative that this is clear.

cheers
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alviesinger42
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Re: Thermostat opening temperature

Post by alviesinger42 »

Thanks guys,

Sorry I have been away at sea for the last few weeks hence the lack of follow up.
Brucey was spot on, although I had checked the thin hose from radiator to expansion tank, I didn't check the thin port at the top of the radiator it connects to. On closer inspection this was blocked.
I have also just changed the stat anyway for peace of mind.

I now need to remove and replace the remainder of the old coolant, but cannot find the drain point on the engine block. I have the car up in the air and I thought I was looking for a 19mm bolt on the exhaust side of the block, towards the rear of the car. I cannot see anything at that end of the block, however there is one on the exhaust side at the front of the engine. Is this where it is located on a UK car ?

Cheers

Richard
1986 635csi auto
alviesinger42
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Re: Thermostat opening temperature

Post by alviesinger42 »

Scratch that, I have found it, exactly where it was meant to be.

Richard
1986 635csi auto
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