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Removing Your Thermostat on your Mercedes Benz
 
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Pelican Technical Article:

Removing Your Thermostat on your Mercedes Benz

Steve Vernon

Time:

1 hour1 hr

Tab:

$35

Talent:

**

Tools:

10mm socket, Flathead screwdriver

Applicable Models:

Mercedes-Benz 190E (1984-93)

Parts Required:

Thermostat, gasket

Hot Tip:

Have a friend help

Performance Gain:

Engine runs at the proper temperature

Complementary Modification:

Replace older hoses

The thermostat helps control the engines temperature. If your car is running too hot and there is the proper amount of coolant in the car and it is not leaking, or your car is taking a long time to warm up, there is a very good chance your thermostat is bad and needs to be replaced.

The thermostat is located on the top of the water pump between the cylinder head and the power steering reservoir. If you are going to be working on the thermostat, make sure the car is cool and not under pressure. Working on a hot engine or one under pressure can cause serious harm (coolant is also very toxic) and should never be attempted. Coolant needs to be collected and disposed of in accordance with your local regulations as pouring coolant down a drain or into the street is illegal. Also, be sure to wash your hands thoroughly after working around it.

With the car cool, begin by releasing any residual pressure in the system by removing the cap on the coolant reservoir. Note: Never open the cooling system when the car is still warm. Next, move to the thermostat itself and unscrew the large hose coming out of the unit. There may be a little coolant that spills so be ready for it with a rag. With the large upper hose removed, move to the small hose going from the top of the thermostat to the reservoir and remove it.

There are three 10mm bolts holding the top of the thermostat to the housing. These can stick a little as coolant can get in them and corrode them. Remove the bolts and wiggle the top from the housing.

With the top removed you can pull the thermostat up and out of the housing. The inside of the house can get a little corrosion which you should clean up before installing the new unit. Always install a new gasket, even if you are just inspecting and reusing the old thermostat.

Check all your hoses while performing this job and replace any that are old, getting hard or brittle or beginning to weep.

Installation is the reversal of removal.

Once the car is cold, begin by removing the cap on the coolant reservoir to release any residual pressure.
Figure 1

Once the car is cold, begin by removing the cap on the coolant reservoir to release any residual pressure.

Remove the clamp and large hose coming out of the thermostat housing (yellow arrow).
Figure 2

Remove the clamp and large hose coming out of the thermostat housing (yellow arrow).

Remove small hose going from the top of the thermostat housing to the coolant reservoir (red arrow).
Figure 3

Remove small hose going from the top of the thermostat housing to the coolant reservoir (red arrow).

Next, remove the three 10mm bolts securing the top of the thermostat to the base (yellow arrows).
Figure 4

Next, remove the three 10mm bolts securing the top of the thermostat to the base (yellow arrows).

You can now separate the housing, revealing the thermostat.
Figure 5

You can now separate the housing, revealing the thermostat.

Pull the thermostat up and out of the housing.
Figure 6

Pull the thermostat up and out of the housing. You should clean the contact surfaces of the housing of any gunk or corrosion. Always install a new seal or gasket even if you are reusing your thermostat. Installation is reversal of removal. Don't forget to replace any coolant you may have lost.

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Comments and Suggestions:
frenteacasa Comments: Please, should the thermostat ball valve oriented in a specific way?
June 10, 2015
  Followup from the Pelican Staff: The small vent? Always place it at the highest point. - Nick at Pelican Parts  
Chuck Comments: What should I use to clean the inside after pulling the thermostat out?
November 23, 2014
  Followup from the Pelican Staff: soap and water. - Nick at Pelican Parts  
Bakkied Comments: Good site how do I bleed the cooling system on 190e and wat specs must be on thermostat temp 190 e 95 aut model please help
September 24, 2014
  Followup from the Pelican Staff: Try this tech article

http://www.pelicanparts.com/techarticles/Mercedes-190E/23-WATER-Coolant_Flush/23-WATER-Coolant_Flush.htm - Nick at Pelican Parts
 
Ilya Comments: I changed my Thermostat, and now engine showing higher temperature. Why is it happening?
Before temp showed 80 on highway, and now its above 80 on highway
June 18, 2014
  Followup from the Pelican Staff: There could be air trapped in the system. Try bleeding it. - Nick at Pelican Parts  
Matt Comments: if i replace the thermostat do i have to adjust it or something? or i just buy a new one and install it as is?
May 7, 2014
  Followup from the Pelican Staff: No adjustment needed. Install new one and fill and bleed cooling system. - Nick at Pelican Parts  
vincent Comments: Thank you very much my garage man said this is a lot of trouble, I have been freezing for the last 2, years and
a damp car. Thank you so much I will do it my self.
February 12, 2014
  Followup from the Pelican Staff: Thanks for the feedback, glad we could help. - Nick at Pelican Parts  
Wale Comments: Please, what size of thermostat centigrade is good to replace the old one in Mercedes Benz 190 E
September 27, 2013
  Followup from the Pelican Staff: Most thermostats are about 180 (82 C) degrees before they open. If you are in a hot climate you may want to go a little lower and a cold climate a litting higher. You cannot change it too much becasue it affects the fuel injection systems. - Kerry at Pelican Parts  

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