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Pelican Technical Article:

Removing Your Thermostat

Nick Czerula

Time:

3 hours3 hrs

Tab:

$200

Talent:

***

Tools:

Set of sockets, wrenches, screwdrivers, trim removal tools

Applicable Models:

BMW 323Ci Coupe/Conv (1999-00)
BMW 323i Sedan/Wagon (1999-00)
BMW 325Ci Coupe/Conv (2001-06)
BMW 325i/xi Sedan/Wagon (2001-06)
BMW 328Ci Coupe (1999-00)
BMW 328i Sedan (1999-00)
BMW 330Ci Coupe/Conv (2001-06)
BMW 330i/xi Sedan (2001-06)

Parts Required:

Thermostat, hoses, engine coolant

Hot Tip:

Work with a cool engine

Performance Gain:

Car will cool down again

Complementary Modification:

Change radiator hoses

BMW E46 cooling system components include:

  • Radiator and coolant overflow tank
  • Belt driven water pump bolted to the front of the engine block
  • Electric cooling fan attached to rear of radiator - the cooling fan is controlled by the engine control module (ECM) via an output final stage
  • Automatic transmission models: Belt driven fan attached to front of water pump, viscous clutch controls fan speed based on engine temperature and rpms
  • Electrically heated thermostat
  • Automatic transmission cooler (heat exchanger)
  • Heater valve and heater core (for climate control)
  • Coolant level sensor inside expansion tank
  • Coolant temperature sensor at cylinder head
  • Radiator outlet temperature sensor
  • Coolant hose and lines

The ECM controls and monitors operation of the thermostat. It controls thermostat function according to a map and allows the engine management system (DME) to raise the engine operating temperature quickly and precisely to the optimal range and to maintain it there for maximum efficiency and minimum emissions. 

If a fault occurs in the thermostat, a fault code is stored in the ECM, usually with a description of "map cooling circuit." A fault code can be present, yet the vehicle will lack any cooling system issues, such as overheating. This is because the thermostat has a fail-safe mechanical function as well. If you have this fault code, replace your thermostat and bleed your cooling system. Other symptoms of a faulty thermostat are engine overheating, slow to warm up and lack of heat. 

The thermostat is integrated with the thermostat housing. The two are replaced as a unit. It is mounted to the cylinder head at the front of the engine. 

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches. 

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If  you are working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability. 

Vehicle models change and evolve, as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Drain the cooling system. See our Pelican Parts Technical Article on Flushing Your Coolant.

Remove the cooling fan shroud. See our Pelican Parts Technical Article on Removing the Radiator Fan.

If you are looking for more Technical Articles to diagnose or repair cooling issues please visit our E46 page.

When replacing the thermostat (yellow arrow), I suggest replacing both coolant hoses (red arrows) that connect to it.
Figure 1

Tip: When replacing the thermostat (yellow arrow), I suggest replacing both coolant hoses (red arrows) that connect to it. Many times I have replaced a thermostat, filled and bled the cooling system, only to find an o-ring on one of the coolant hoses that has failed and now leaks.

Drain the cooling system. See our Pelican Parts Technical Article on Flushing Your Coolant. Remove the cooling fan shroud. See our Pelican Parts Technical Article on Removing the Radiator Fan.
Working at top of thermostat, locate the electrical connector (yellow arrow).
Figure 2

First, drain the cooling system. Next, remove the cooling fan shroud.

Working at top of thermostat, locate the electrical connector (yellow arrow).

Next depress the electrical connector retaining clip and remove the electrical connector from the thermostat.
Figure 3

Next depress the electrical connector retaining clip and remove the electrical connector from the thermostat.

Working at radiator hose, using a flathead screwdriver to remove the coolant hose retaining clips.
Figure 4

Working at radiator hose, using a flathead screwdriver to remove the coolant hose retaining clips.

Pull the retaining clips out until they rest at a stop (yellow arrow).
Figure 5

Pull the retaining clips out until they rest at a stop (yellow arrow).

Next, remove the coolant hoses from thermostat.
Figure 6

Next, remove the coolant hoses from thermostat. This can be tricky. The hoses have been attached to the thermostat for quite a while and may not come off easily. You will want to pull the hose off, while rocking it back and forth. Be careful not to damage the hose if you plan to reuse it. Once the hose moves off the thermostat slightly, you can use a flathead screwdriver to gently slide the hose off while pulling. Now be very careful with this technique as everything you are prying on is made of plastic and can break.

11 mm).
Figure 7

Next remove the engine lifting eye nut (yellow arrow, 11 mm). This will help with removing the thermostat.

Now, remove the two thermostat mounting fasteners (13 mm) (upper bolts, yellow arrows).
Figure 8

Now, remove the two thermostat mounting fasteners (13 mm) (upper bolts, yellow arrows).

Remove the two thermostat mounting fasteners (13 mm) (lower bolts, yellow arrows).
Figure 9

Remove the two thermostat mounting fasteners (13 mm) (lower bolts, yellow arrows). Now you can remove your thermostat from the engine. Be prepared to catch any dripping coolant.

Using a plastic scraper, clean the thermostat sealing surface.
Figure 10

Using a plastic scraper, clean the thermostat sealing surface. It is important not to use a metal scraper or razor blade here. You could damage the sealing surface which can cause the thermostat seal to not seat properly, resulting in a leak.

Install the new thermostat and evenly tighten all the fasteners. Install the engine lifting eye nut and tighten. Install the coolant hoses - listen for an audible click to confirm the clips have engaged. A small amount of new coolant can be used to lubricate the coolant hose o-rings as this will make installing the hose easier. Connect the thermostat electrical connector. Install your fan shroud and then fill and bleed the cooling system. Remember to check your cooling system for leaks and top off the coolant when complete.
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Comments and Suggestions:
veteran Comments: I have my e46 having hard start. Wouldn't rev well. What can I do? I've replaced the ECU, coil, spark plugs, AFM.
July 27, 2017
  Followup from the Pelican Staff: Is the check engine light on or flashing when the problem is present? Sounds like an engine misfire. I would check spark, fuel and compression on all cylinders.
- Nick at Pelican Parts
 
Syed Comments: Hi
My BMW 318i 2002 cold start when you turn ignition on temperature guage high red not starting the car
July 4, 2017
  Followup from the Pelican Staff: That can be a faulty DME or a DME not communicating. - Nick at Pelican Parts  
Gilbs Comments: I have an issue where the coolant seems to be boiling in the expansion tank and steam coming from the expansion tank lid. I recently replaced the water pump then the rad and then the expansion tank and the coolant level sensor.
It's a manual.
Before the expansion tank was changed it was absolutely fine until the expansion tank cracked
From what I've read I can't figure out if there's another temp sensor in the bottom of the expansion tank on the manual. And if so did I throw it away with the old expansion tank?
It's a 2002 320ci. I'm in the UK and we've had 27*C recently.
I'm sure I've bled it properly and added BMW coolant, although only 1litre of coolant and the rest water. I know I know 50/50 coolant etc etc, but would that really cause this problem as it was fine before the expansion tank went.
Thanks in advance, loving you're work!!!
June 20, 2017
  Followup from the Pelican Staff: if you have bled the system, it shouldn't get that hot. I would pressure test the cooling system. If the system will not hold pressure and there are no external leaks the head gasket may be faulty.
- Nick at Pelican Parts
 
CrashX2 Comments: Hello, I recently replaced the thermostat, the older one was stuck, it looks like somebody added some leak sealing which cause this. However after two months of normal riding the new thermostat is stuck too. Why or what is causing the thermostat getting stuck? The coolant system was replaced, new electric fan, new hoses, new radiator, water pump was in good conditions and working properly. Coolant added was "WOLF
COOLANT-36°CLONGLIFE G12+" link:

https://www.wolflubes.com/EN_EU/products/product_50101.aspx?cat=17563

Also, before the thermostat started getting stuck I noticed low coolant level, no white smoke, no white residues in the coolant, just lower level, I added distilled water about less than a half galon. So no much coolant was lose but low level instead. Maybe because the system was recently bleeded and needed more coolant? Or is this coolant evaporating faster than needed, or is getting burned somewhere?

I am afraid the thermostat keeps getting stuck. Any advice and help how to resolve this? Thanks
May 22, 2017
  Followup from the Pelican Staff: i WOULD DRAIN THE COOLANT, SEE IF THERE ANY COMTAMINANTS. tHEN ADD bmw LONG-LIFE COOLANT. I would ALSO pressure test the cooling system. If the system will not hold pressure and there are no external leaks the head gasket may be faulty. - Nick at Pelican Parts  
Clay Comments: Thank Casey, I went ahead an change the thermostat and it runs better but am loosing coolant from the expansion tank so I went and purchase a cap from advance but it's not venting the pressure from the system. Thank you a bunch.
April 4, 2017
  Followup from the Pelican Staff: On a part like the expansion tank cap, I usually go with Genuine BMW. Typically I believe, the cap would not need to vent the pressure from the tank unless it is over filled. - Casey at Pelican Parts  
Clay Comments: Hi good.I am having a issue with my 03 530i overheating it will run for about 40 minutes if the heater is on if the heat is off give it 20 minutes. The expansion tank would overflow so I went to advance and bought a expansion tank cap after changing the cap I went for a ride 15 minutes in the ride my radiator blow and I realize that the fan wasn't working so I add some water and keep adding till I make it home, the weekend I went and get radiator and replace now my radiator hose are getting really hard so I let is cool and switch the cap I soak and attempt to clean the old cap I now realize that the old cap release pressure some what. I put it an the computer and the give code p1619 but my thermostat housing doesn't have a thermostat in it can that be the problem for the overwhelming.
April 3, 2017
  Followup from the Pelican Staff: I've heard that running without a thermostat CAN cause overheating but have never personally experienced that. I would be looking at the water pump, fan clutch, and making sure that you properly bled the system after your repairs. - Casey at Pelican Parts  
Innocent Comments: Hello everyone!
I have a problem with my 325i e46 model.
It keeps on overheating.
At first they said it was a clutch fan them I changed it. Now they telling me other stories.
Please guys help me.
February 24, 2017
  Followup from the Pelican Staff: Haha! Funny pic... This sounds like the classic thermostat, and or water pump failure. It is typical of shops to try the cheapest possible failure item first then see how it goes. Not my favorite method but one that is common at indie shops and the dealer. - Casey at Pelican Parts  
swyaze46 Comments: will its open at 95?
February 20, 2017
  Followup from the Pelican Staff: It is map controlled by the DME and given various driving conditions the DME can open the thermostat earlier. I cant remember what the normal opening temperature is, the parts' description says 97 degrees Celsius, which I believe is the temperature that it should be fully open. - Casey at Pelican Parts  
jack Comments: hello,
How much coolant dose the 2003 325ci need? I need to change the thermostat and would like to flush the radiator coolant.
Thanks
November 2, 2016
  Followup from the Pelican Staff: See this:

http://www.pelicanparts.com/BMW/techarticles/BMW-3-Series-E46/32-WATER-Flushing_Your_Coolant/32-WATER-Flushing_Your_Coolant.htm - Nick at Pelican Parts
 
Sumfun Comments: correction....thermostat labor is $327.00
August 3, 2016
  Followup from the Pelican Staff: Ok, thanks. - Nick at Pelican Parts  
Sumfn Comments: I've been having shifting issues with my 2003 M3 SMG. Just received call from private certified BMW shop telling me I need a new relay & Salmon 5 prong. Parts $512.00 and labor $545.00 Does that sound right? Also needs new thermostat parts $102.00, labor $237.00 and coolant $25.00
Would like input if this shop is charging too much.
August 3, 2016
  Followup from the Pelican Staff: I am not sure what the repair will cost in your area. Call a few shops and ask for a quote. It is also a good idea to have them confirm what the issue is. Give our parts specialists a call: 1-888-280-7799, They will help you price out the parts.
- Nick at Pelican Parts
 
jay Comments: hello thanks for your useful advise could you please recommend which epoxy to use and sand grit. Thanks for the advice. I did search on net and jd weld but they have so many and I don't want to use wrong one.


jay Comments: hi I removed my thermostat and clean engine area where it sits but I notice it has pitting what are my options? I have sent link to show what I mean.

http://i68.tinypic.com/szifmd.jpg

I cannot feel it while I rub my finger on it. so will the gasket stop it from leaking
May 7, 2016
Followup from the Pelican Staff: Clean the area well, then sand it gently just enough to roughen it up. Add epoxy to the pitting and sand flat. Use a straight edge tool to confirm it is perfectly flat. It should seal. - Nick at Pelican Parts


May 10, 2016
  Followup from the Pelican Staff: I am no epoxy expert, we always had single use cups around. Not sure it is available in small portions, usually came in a tube of 20.



Give our parts specialists a call at 1-888-280-7799. They can figure out a good epoxy.

For sandpaper, use a fine grit wet sand paper.
- Nick at Pelican Parts
 
jay Comments: hi I removed my thermostat and clean engine area where it sits but I notice it has pitting what are my options? I have sent link to show what I mean.

http://i68.tinypic.com/szifmd.jpg

I cannot feel it while I rub my finger on it. so will the gasket stop it from leaking
May 7, 2016
  Followup from the Pelican Staff: Clean the area well, then sand it gently (just enough to roughen it up. Add epoxy to the pitting and sand flat. Use a straight edge tool to confirm it is perfectly flat. It should seal. - Nick at Pelican Parts  
DJ Lil BASTARD Comments: My sports wagon thanks you and Casey Gervig for the help
March 28, 2016
  Followup from the Pelican Staff: Casey is a swell guy! - Nick at Pelican Parts  
Jon Comments: Oops, just noticed you're talking about an 06 Z4. Nevermind.
February 19, 2016
  Followup from the Pelican Staff: This article is for BMW E46 3-Series models. - Nick at Pelican Parts  
Jon Comments: @lilady - You may have a cracked coolant expansion tank. It's a very common E46 problem because of the way it is mounted. You hit a bump, tank cracks open, all the coolant floods out. Has happened to me on both of my E46 BMWs. Search part #: 17-11-7-573-781-M58
February 19, 2016
  Followup from the Pelican Staff: Thanks for the input on this one. We appreciate the help. - Nick at Pelican Parts  
lilady Comments: I have a bmw2006 z4 3.0i I was driving my car and happend to look at gauges and my temp was all the way in the red zone . I pulled over and let it sit my friends brought me coolant my car was normal heat niot even two seconds my car started going all the way hot then in between then to normal and back to hot . can you please tell me whats going on ? i also got a code p1447 please tell me how to fix these problems
February 18, 2016
  Followup from the Pelican Staff: You could have a faulty thermostat or a cooling system leak. I would pressure test the cooling system. If the system will not hold pressure and there are no external leaks the head gasket may be faulty. - Nick at Pelican Parts  
morpex Comments: Hello,

I need to change a thermostat. I've bought a new one. But there is a problem. Thermostat I've bought opens at 97*C, while others thermostats for this engine opens at 85*C.
Thermostat is made by Vernet France.
Is there a big possibility, that the engine will start overheating when the weather will be hot?
February 12, 2016
  Followup from the Pelican Staff: It shouldn't overheat, but may run hotter.

Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
Tonton Comments: My bmw e46 overheating after 15mins drive escially when my a/c is on... The aux fan is working fine, no water leak.. Can you help me with this?
August 30, 2015
  Followup from the Pelican Staff: The engine cooling fan may be faulty. If the condenser fan is on, check that the engine cooling fan (mechanical or electrical) is functioning. - Nick at Pelican Parts  
Helps Comments: My bmw 2006 just started overheating like i oour antifreeze than the fans gocrazy over heats auivk like if it goes in nout like the thermostat or something
August 18, 2015
  Followup from the Pelican Staff: Could be the thermostat or water pump. Are there any fault codes stored? - Nick at Pelican Parts  
Kanch Comments: Please can you send me a pic of the timing marks for timing chain replacement.
Where can I obtain an engine repair manual for the E46 318i 2002 engine
May 18, 2015
  Followup from the Pelican Staff: I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
Realdeahl Comments: I replaced my thermostat as the car was running cool64-70C at highway speeds. The car now heats to normal operating temps 93-96 for about 30 minutes and the heater works normally. Then the temperatures drop to 80C at highway speeds and the heat blows colder air. Any suggestions on where to look next?
February 11, 2015
  Followup from the Pelican Staff: You are maintaining a some what warm engine temp. I would do a few things. Be sure the thermostat you installed isn't defective, check if there is air trapped in the cooling system, and check if hot engine coolant is getting to the heater core when the heat cools off. - Nick at Pelican Parts  
JLH Comments: Last and most important question: Does the line going to the Heater Valve come directly from the engine block? Or is there something in between the hot water coming from the to the heater valve? This is the only thing I have left to diagnose. my control mod in the car runs fine, fan works on all levels, all vent movement is fine
January 30, 2015
  Followup from the Pelican Staff: Yes. It connects to the engine, If i remember correctly, under the intake. - Nick at Pelican Parts  
JLH Comments: Note prior to replacing parts mentioned below heat was hotUpdate: I flushed the core by running water from the outlet hose to the exp tank thru the core and out the inlet hose from the heater valve. Some crud came out at first but then clear water. I then went the opposite direction and clear water. I ran water through the Heater valve and it flowed clear which means vavle is open - Correct?. Hooked it all back up, briefly bleed the system again started up and it sucked down what was in the exp tank believe that means my pump is good filled up coolant. Now I have slight heat that gets warmer at higher RPMs. Any Ideas? Air Pocket? or the new water pump bad?
January 30, 2015
  Followup from the Pelican Staff: Well, it sounds like everything is working, yet you have no heat. I would remove the hose to the heater core, turn heat on high, then install a pressure gauge and see if you have pressure. Look for about 6 psi. - Nick at Pelican Parts  
JLH Comments: Per below, If the thermostat was stuck open wouldn't my Eng Temp Gauge run Cold and not Straigt up at Noon perfect running temp?? It takes no time less than 2-5mins running down the road for the car to get to optimimal running temp? Would that still happen if stuck open?


Comments: 01 325I, bought thermostat getting a p1620 code but that could have been before Tstat issue. Now I have no heat. Car runs great. Engine Temp is at Noon at all conditions. Can bad thermostat make my heat not work
J
anuary 28, 2015
Followup from the Pelican Staff: Yes, if it is stuck open. Is there hot coolant getting to the heater core? - Nick at Pelican Parts
January 29, 2015
  Followup from the Pelican Staff: It could run cold, or warm. Your gauge is not a gauge, more of a operating temp switch. The car would take longer to heat up if the thermostat was faulty.

Is there hot coolant getting to the heater core? - Nick at Pelican Parts
 
JLH Comments: 01 325I, bought thermostat getting a p1620 code but that could have been before Tstat issue. Now I have no heat. Car runs great. Engine Temp is at Noon at all conditions. Can bad thermostat make my heat not work
January 28, 2015
  Followup from the Pelican Staff: Yes, if it is stuck open. Is there hot coolant getting to the heater core? - Nick at Pelican Parts  
Derek Comments: I have to do this every year on my 2001 325xi e46 wagon winter edition. I have tried all different t-stats Big $ ones and cheap ones, same results. Thermostat stuck in the open position. Is there something I can do to help the thermostat last longer than a 1 year?
November 6, 2014
  Followup from the Pelican Staff: Have you used a BMW part? I can;t imagine why the part would fail every year. Unless you are using dirty water when mixing the coolant. - Nick at Pelican Parts  
dandoe Comments: I did this diy the other day, and had no problems. Now my car is shifting really hard and idles like a Chevy big block. Also replaced the power steering pump. Any thoughts?
June 16, 2014
  Followup from the Pelican Staff: You may have left something unplugged or misconnected. I would start by checking the DME for fault codes. If the system is not working properly, a fault code will be set. This will be your best bet when diagnosing.
- Nick at Pelican Parts
 

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Page last updated: Mon 8/21/2017 02:22:22 AM