Author Topic: Thermostat  (Read 195 times)

Punker

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Thermostat
« on: 17 March 2020, 01:14 PM »
Hallo Guys,

I took a 100 km ride the last days. The temperature here in March was about 8 Grad celsius. I pretty often regonized that it takes a very long time and distance until the engine has reached the operation-temperature of 175 Fahrenheit (my 6.9 is from the states).

My question: how do I ensure that the thermostat is working as he should? Thanks a lot for recommendations and information.

Greetings from Hamburg
Björn
1978 Mercedes 6.9 # 4616 - black/black leather
BMW R 25/3

ptashek

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Re: Thermostat
« Reply #1 on: 17 March 2020, 01:47 PM »
Hallo Guys,

I took a 100 km ride the last days. The temperature here in March was about 8 Grad celsius. I pretty often regonized that it takes a very long time and distance until the engine has reached the operation-temperature of 175 Fahrenheit (my 6.9 is from the states).

My question: how do I ensure that the thermostat is working as he should? Thanks a lot for recommendations and information.

Greetings from Hamburg
Björn

A sure, bit invasive, way is to take it out of the housing and dipping in a jar of just boiled water. If it opens fully (the plunger moves all the way up), it's OK. It may open partially or not at all, at which point you'd need to replace it.
1993 "Pearl Blue" W124 280TE
1979 "Icon Gold" W116 450SE (history, resto)

daantjie

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Re: Thermostat
« Reply #2 on: 17 March 2020, 02:11 PM »
You will have to quantify "a very long time and distance".  However in the meantime I can tell you from my experience that @ 8 or so Celsius ambient, mine takes about 15 - 20 minutes to get to the middle of the range with low - moderate speeds being driven,  Remember this is a huge chunk of metal that needs to get warmed up so it does take a fair bit of time especially at cooler ambient temps.
« Last Edit: 17 March 2020, 05:49 PM by daantjie »
Daniel
1977 450 SEL 6.9 - Astralsilber

revilla

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Re: Thermostat
« Reply #3 on: 17 March 2020, 04:17 PM »
Sure it takes some time to fully warm up, however, according to the description if it takes long to reach op temp the thermostat might be stuck in the open position and not in closed position. If closed the symptoms would be the opposite (over heating).
I would remove it from the housing as suggested by Lucas and inspect it and clean it. Anyway they are still available new at reasonable price (around 25€). I recently changed mine. When removing the cover do so very carefully as the screws are long and thin and tend to deform under torsion stress.
Best of lucks.
Robert
W116 1977 280SEL & 1979 280SE

Punker

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Re: Thermostat
« Reply #4 on: 18 March 2020, 01:46 PM »
Thanks a lot for your recommendations. Just in case I ordered a new one online. It is not an expensive spare part. Daantjie, the time you estimated (15 - 20 minutes) at these outside temperaturesist the figure I had guess for the time my car needs.

I want to change water coolant and all the tubes anyway within the next days (Unfortunatly I should have time) so I can change the thermostat too.

Thanks a lot again for your quick response.

Greetings
Björn
1978 Mercedes 6.9 # 4616 - black/black leather
BMW R 25/3

BCDC

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Re: Thermostat
« Reply #5 on: 18 March 2020, 02:19 PM »
My car takes only about 6 - 8 mins of slow driving to show normal temp on the gauge. I feel 15 to 20 is too slow and the thermostat is indeed stuck open. Oil temp however takes much longer, so don't drive the car too hard early on until everything is warmed up. IMO.

BC
1978 280SE Cream with blue leather interior. With SLS

daantjie

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Re: Thermostat
« Reply #6 on: 18 March 2020, 04:28 PM »
Thanks a lot for your recommendations. Just in case I ordered a new one online. It is not an expensive spare part. Daantjie, the time you estimated (15 - 20 minutes) at these outside temperaturesist the figure I had guess for the time my car needs.

I want to change water coolant and all the tubes anyway within the next days (Unfortunatly I should have time) so I can change the thermostat too.

Thanks a lot again for your quick response.

Greetings
Björn

Maybe take some pics and post them up if you can.  I have this job on "the list" too, should not be a tough job as access is super good, however as others have noted the bolts may be stuck due to aluminium and steel corrosion so be very careful, go slow with lots of penetrant spray like PB Blaster.
Daniel
1977 450 SEL 6.9 - Astralsilber

Punker

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Re: Thermostat
« Reply #7 on: 20 March 2020, 01:46 PM »
Thanks for advice . Will try to make some pictures. Greetings
Björn
1978 Mercedes 6.9 # 4616 - black/black leather
BMW R 25/3