I decided to replace the thermostat because I am having bad fuel mileage (17-18 mix 65% highway 35% city) and my engine temperature won't go over 80C and I read somewhere that a bad thermostat may be the cause. (Before that I thought the cooler engine temp is the better for the engine).
The job is simple for DIY rookie like me, just remove 3 10mm screws (# 1,2,3 on the pic) on the housing cover using a rachet with a long extension. That should be done on a cold engine.
Unflug connector #4 else the cable will be in the way when removing the housing cover.
The cover and the old thermostat may sit tight perhaps because of the gasket sticking tightly, just use a little force. The spillage is minimal, about a cup of coolant.
Remove the thermostat and put the new one together with a new gasket in.
Attach the cover, start the engine and check for leak.
1: new thermostat
2: base of housing
3: housing cover, displaced
4: old (bad?) thermostat.
hoping for some mileage improvement.
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W210 1996 E320 Exterior Smoked Silver, Interior Mushroom.
133.5 K miles as of April/08.
Last edited by texholdem : 02-05-2008 at 10:49 PM.
You have the m104 engine,not noted for as high mpg
like the m112.Thermostat set for 87c typically runs at about 80c in the cooler months about 90c in the summer.
No harm changing it,I just don't think you will see much of an improvement.Up your tire pressure to 32 front and 38 rear.Are you running non oe wheels like 18's they will kill mpg.Clean you mass air sensor.Have you changed your o2 sensors?Clean air filter from autohausaz.com.
good luck
Before replacing thermostat I would check the temperatures with infra-red thermometer.
I did the trick with my Ford Powerstroke. Some company makes big money selling 185F thermostats to replace the 170 stock (from what I remember). On my check the new thermostat opens at 175F, what is only 5 degrees higher, than the OEM. The salesman told me this is how it suppose to be. Without the thermometer I would feel the power gain for sure.
good job texholdem, nice work.
yeah, that doesn't seem excellent gas mileage for combined city/highway. thermostat could be the problem. also you could be due for a tune up? i have the m104 in my e320 and i get 18mpg all city driving, and if it's mix city/highway i usually get above 20mpg, and if it;s all highway usually it is 27-28mpg. on my s320 which is a lot heavier than the e320 i get about 16-17mpg city, and they both have the same engine. also gas is different from state to state, so that could be part of it too.
like the m112.Thermostat set for 87c typically runs at about 80c in the cooler months about 90c in the summer.
No harm changing it,I just don't think you will see much of an improvement.Up your tire pressure to 32 front and 38 rear.Are you running non oe wheels like 18's they will kill mpg.Clean you mass air sensor.Have you changed your o2 sensors?Clean air filter from autohausaz.com.
good luck
The tank flap says for tire pressure 29 front and 32 rear, is it OK to raise to 32 front and 38 rear?
I have stock tires 215/55/16, gonna change air filter today.
In the case of no improvement, I'll consider the O2 sensor as next.
Thanks!
Last edited by texholdem : 02-06-2008 at 07:27 AM.
is fine for good tires.If ride is to firm set them at 32 front and 36 rear.The best investment to proper tire inflation is a good gauge not one of those cheap pencil ones but a good 20 buck quality one.
A lazy o2 sensor will really affect mpg and they are 80-100k mile maint items.
Have you ran a can of seafoam injector through a tank of fuel?Dirty injectors kill mpg. ohlord
is good stuff also
seafoam at autozone,napa etc.
With that engines higher rpm power curve a lot of members have found a few mpg by avoiding jack rabbit starts,ease away from the lights and gradually work the car into its power band.
Vehicle: 2001 SLK 320(93K Miles), 2002 E320 Special Edition(112K Miles)
Location: South Bay Area,L.A., CA
Posts: 968
With 38 at the rear, you are bound to get some center thread wear. Frequent back to front rotation should take care of it.
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