Zoso's Thermostat Replacement

[DesktopDave]

Thanks again to Zoso for an excellent writeup.  As his domain is down, I've taken the liberty of posting this how-to on our site.  If he (or anyone else) has trouble with that, please contact me and I'll pull the content.


318i Tech Procedure -
Thermostat Replacement &
Coolant Change
  I've had issues with heat in my 318i since I purchased it. The temp needle on the instrument panel would barely leave the blue on cold days and would barely make it to the 1/4 mark on warm days. In the very cold, the cabin heat was not sufficient and my commute to work was miserable. The floor heat was also sub-standard. Furthermore, a car running cold is not running as efficiently as it could. Shortly after purchasing the car, I went through the papers in the glove compartment and found a repair record where a previous owner brought the car to a shop complaining of poor heat. They replaced the thermostat and the hoses.

  My first step to repairing my heat was to change out the thermostat and coolant. If this doesn't work, my next plan is to test the heater control valve. Located in the passenger side foot well, the heater control valve opens to allow the hot coolant to flow into the heater core. Consider the E30 is closing in on "antique" status, if the coolant was not changed frequently enough and if the wrong type of coolant was used, the heater control valve may be corroded and not opening fully.

  Luckily, my thermostat replacement did the trick in restoring my heat.
  Before I get into the procedure on how to replace the thermostat and change the coolant, I want to talk a bit about coolant. The 1991 318i and all newer BMWs use aluminum components in the cooling system. When replacing the coolant, do not use regular coolant. You must use a coolant that has no nitrites and no phosphates. Pony up and spend $20/gallon on the BMW coolant from the dealer. Why is it necessary to use this special coolant? BMW released a tech bulletin listing a problem that results in a green-gel that results from using normal coolant and water in a BMW. You can imagine that a green-gel doesn't cool properly. Regular green coolant with all the nitrites and phosphates are also more conducive to electrolysis and the aluminum components of our BMW cooling systems are more susceptible to damage from electrolysis than the cast iron components of other vehicles. Using distilled water instead of tap water also keep the amount of minerals in your cooling system lower. At the bottom of this page is a link to a tech article on Pelicanparts.com that discuses the problems of electrolysis and standard coolant in more depth.

  Summary of the last paragraph: Use BMW coolant and distilled water.
  BMW Parts:
1 Gallon BMW coolant
11537511580 88 Degree C Thermostat
11531721218 O-Ring
11531721172 Gasket
  Click on the thumbnails for larger pictures.
         
   
The first step is to remove the underbody panel. If you   are going to radiator, give the fluid a direct shot to your catch bucket.   There are two 10mm plastic nuts holding the edges up.
             
   
     There are two more holding the sides on. There are some   small screws that hold the edges of the panel to another panel. You can   unscrew these with a 7mm socket in your hand.
             
   
     Here is a picture of the under panel removed. This step   doesn't take much time and makes working down there much easier.
             
   
     Remove the cap.
             
   
     Using your hand, slowly open the valve. Coolant will start   trickling out. Use the valve to control the flow of all the coolant leaving   the radiator.
             
   
     Most people don't know that good amount of radiator fluid is always inside   the engine and that if you drain the radiator and not the engine block, you   are not truly replacing your coolant. The plug is 19mm and located on the   rear, passenger side of the M42 engine, somewhat behind the exhaust headers.

   I tried to moderate the flow of coolant from the block, but it ended up   everywhere. It splashed over the exhaust, ran down to the car, splashed on me   and soaked everything. You can enlist your local neighborhood pets to lick it   up for you. If you are really sadistic, you can allow your wife/girlfriend's   prized pet to help you.  (Just joking here - hopefully by now we all know that animals are attracted   to the taste of anti-freeze, but it ends up killing them by shutting down   their kidneys.)
             
   
     Unplug the host leading from the radiator to the   thermostat.
             
   
     Unplug the other hose. Note that more coolant will escape   so have a catch basin ready below the hoses. This job is messy.
             
   
     I removed the radiator shroud to make the access easier with a 10mm socket.   This is not necessary. The Bentley manual (the E36 one for the M44 engine)   recommends removing the fan to get access to the thermostat. I tried this but   I couldn't get the fan off. You need a 32mm wrench and a method of holding   the fan still while you give the nut between the pulley and the fan blades   and quick impact in the clockwise direction if facing the front of the car.   The threads are reverse threaded. The only tool I had that would fit this nut   was a large adjustable wrench. I ended up never getting the nut to budge a   millimeter and I managed to bend and break off several of the aluminum fins   of the fan clutch.
   Luckily, Bentley doesn't know it all.
             
   
     Remove the brackets and the wires that pass in front of   the thermostat housing. Use a 10mm socket. There are 4 bolts holding the   thermostat housing to the engine block. Pop the thermostat housing off the   engine block.
             
   
     Here is my old thermostat. Note the orientation and direction of the old   thermostat while taking it out of the block. You may need to put the new one   in the same direction. Evidently some thermostats have marks for which way   should go up. This thermostat was an 80 degree thermostat, not 88 like it   should have been.

   This picture is great. It shows a couple of things. First, the previous   owner put the green crap in the car, not the good blue BMW coolant. I really   should have flushed my system but it was far below freezing outside and I   wasn't about to flood my inside workspace.
   
Secondly, notice the "No Oil" written on the block? I'm pretty   sure at some point my engine was rebuilt. Whatever - as long as they did it   right. It could be a good thing to have new chains and seals.
             
   
     Clean the thermostat housing surfaces so that the new seal   will not leak.
             
   
     Place the new seal on the new thermostat. I had a ton of issues with this.   I think the place I ordered my thermostat and seals shipped me the wrong   seal. The seal they gave me had a notch and I could surround the thermostat   edge with the seal. It looked right, but the thermostat never sat in the   block like the old thermostat did. I decided to press on and reassembled the   unit. The next day I bought distilled water and tried it. Coolant immediately   spilled all over the floor.

   I ended up taking it all apart. I took the seal off and while thinking of   what to do, I noticed that there was another seal in the box that the   thermostat arrived in. It was a round seal that fits on one side of the   thermostat. Now I could get the thermostat to fit in the block easily.
             
   
     I applied a bit of Permitex gasket maker.
             
   
     I then applied a new seal and managed to carefully angle the thermostat   housing back into place while twisting it to avoid the fan blades that are   always in the way. The use of the Permitex helps because it keep the gasket   in place.
   Reassemble everything and torque the thermostat housing bolts to 9ft-lbs.   Do not over torque.
             
         Add a 50-50 mixture of coolant and water into the radiator until it   reaches the cold like. Turn the key so the car is on, but the engine is not   running. Put the heat on full hot. The valve should open the fluid will empty   from the expansion tank. Add some more.
   Take the bleed screw out. It is right next to the expansion radiator tank   opening. With the car running, keep adding coolant until it starts to run out   of the radiator bubble free.
             
         I ended up having a leak. It was a steady drip off the oil   pan. I don't have the tools to check how much torque I put on the thermostat   housing bolts, but I added some more torque, cleaned off the oil pan, and   restarted the car. After doing this twice, the leaking stopped.
             
             Performed:
         February 13, 2005
        The thermostat replacement worked. The 88 degree thermostat opens later than the old 80 degree thermostat did and my temp needle goes to a hair under 50%. The cabin heat is much improved. I hope to find a few extra MPG, but it will take some time to determine that.
 
Difficulty:
2 /5
(3/5 if you go through all the crap I did with trying to get the fan off, breaking off fan clutch fins, and dealing with the wrong seal)
  Links:
http://www.pelicanparts.com/BMW/techarticles/E36-Coolant_Flush/E36-Coolant-Flush.htm
  Disclaimer:[FONT="] I am not a professional mechanic. Information this page should be used at your own risk and discretion. Different models and model years may be different than my 1991 318i. Read: If you screw your car up following my instructions, sorry. Isn't it sad that in this sue crazy world you have to put a disclaimer on your web page? [/FONT]

[Brian318is]

Dave, you are the man! Thanks so much for the re-ups! These are really great resources!

[DesktopDave]

Thanks, but I just wish that Zoso would get back to me.  While I was searching I found that he'd sold the car this year & the new owner swapped an M52 into it...but he did some really nice work.

BTW, the ho-to doesn't have a good pic of the engine block drain.  I found one at PelicanParts, though it's for an M50.  it's hard to understand, but if you look closely you'll see that he was on the ground under the car looking up from behind the passenger wheel.  The exhaust pipe downtube is on the right.  The bolt is right in the middle beside the freeze plug on the extreme left.

http://www.pelicanparts.com/BMW/techarticles/E36-Coolant_Flush/pic2.jpg

[romeomike]

Here's a picture of the tools that would have made it easier to remove the fan and fan clutch. I've had good luck with my 91 318i doing this.



When I tried removing the fan clutch from a 1990 325iC as part of a water pump and timing belt replacement, I unscrewed only the fan. The fan clutch didn't come off until I removed the water pump, clamped the pump in a bench vise, and worked on the nut/impeller/shaft until the nut finally broke free. The water pump was shot anyway, but I broke the impeller--that's how frozen the nut was.

Since the article was written (2005), Prestone and I suspect other coolant manufacturers have introduced new formulations that are phosphate and nitrite free. Prestone extended-life coolant has all that and is silicate and borate-free as well, and I use it in my two E30s without problems. With the wife's daily driver (2004 325i), I go with the BMW coolant to be on the conservative side.

[aworthybrother]

Hi,
 
Is there any specific position when installing new thermostat?  My new one does not have any marking on which side should be on top.  Thanks.

[DesktopDave]

If it has a bleed hole or jiggle valve, that end is up.  Otherwise it makes no difference.

[aworthybrother]

If it has a bleed hole or jiggle valve, that end is up. Otherwise it makes no difference.

Thank you.  Do you have a pic of what a bleed hole or jiggle valve looks like?

[DesktopDave]

It'd be pretty obvious, a small hole punched in the thermo flange outside the main valve opening.  The jiggle valve has a very small brass tube punched through the flange and crimped loosely around a small bearing.  I don't think most thermo makers use on for the M42 (shame too, they make bleeding a bit easier), just mentioned it in case it did.

[aworthybrother]

It'd be pretty obvious, a small hole punched in the thermo flange outside the main valve opening. The jiggle valve has a very small brass tube punched through the flange and crimped loosely around a small bearing. I don't think most thermo makers use on for the M42 (shame too, they make bleeding a bit easier), just mentioned it in case it did.

Thanks.  I will check my thermostat tonight.

[rjcaptsean]

Here's a pic of the location of the coolant drain plug on the right side of the M42.  It's in the red rectangle on the lower left corner.  (Thanks to Dakon for the pic of his engine)

[aworthybrother]

It'd be pretty obvious, a small hole punched in the thermo flange outside the main valve opening.  The jiggle valve has a very small brass tube punched through the flange and crimped loosely around a small bearing.  I don't think most thermo makers use on for the M42 (shame too, they make bleeding a bit easier), just mentioned it in case it did.

this is what my thermostat looks like, is it supposed to be installed in a specific manner? There is no arrow whic is the top or to be placed in 12'o'clock position.

[DesktopDave]

There is a little dot punched on the front flange, but no hole.  Must not matter.  I'd put that bit at the top so the thermostat frame sits horizontally.  That will help with bleeding.  I'd also back-fill the radiator hose first...the one that goes over to the passenger side.  That helped me tremendously with bleeding out the air.

BMW must have had a reason for omitting the bleed hole, possibly heat the motor up quicker & improve cold start emissions.

That's an odd setup though.  Many thermostats also sit horizontally to prevent air-lock & assist in bleeding out air.  'm sure BMW did it that way for packaging reasons.  The block is shorter in both length and width because of that recessed housing, but it can be rough to bleed the system right.

[bmwman91]

I would like to add a recommendation. Use a paper gasket with some non-curing high-temp spray-a-gasket. If you use any sort of paste, no matter how careful you are in applying it thinly, it will plug up the bleed groove in the housing. About 10 years ago, I was totally unaware that there even WAS a groove because it was caked full of gray gasket paste!

For years I used gasket paste (tube stuff like in the OP). Bleeding was always a lengthy affair where I waited for the engine to fully warm up before...BURRRRRPPPPP! Air was trapped until the thermostat opened. Well, using spray-a-gasket remedied this. 99% of the air bled out within 10 seconds of turning the car on, cold.

Just my $0.02.

[PumpItUp]

I would like to add a recommendation. Use a paper gasket with some non-curing high-temp spray-a-gasket. If you use any sort of paste, no matter how careful you are in applying it thinly, it will plug up the bleed groove in the housing. About 10 years ago, I was totally unaware that there even WAS a groove because it was caked full of gray gasket paste!

For years I used gasket paste (tube stuff like in the OP). Bleeding was always a lengthy affair where I waited for the engine to fully warm up before...BURRRRRPPPPP! Air was trapped until the thermostat opened. Well, using spray-a-gasket remedied this. 99% of the air bled out within 10 seconds of turning the car on, cold.

Just my $0.02.

If you put on Permitex or whatever that blue stuff made for sealing liquid is, and leave it overnight the gasket paste hardens and spreads out, in which case you can cut off the pieces that stick off the edge and plug anything up. Not sure if that hurts the effectiveness of the seal and if you're supposed to put on the part while the sealant is still wet, but it worked for me. But such a small project shouldn't require leaving something overnight.

[91 318i]

I know this is an old thread but the trick that I found out was to drill an 1/8 inch hole in the thermostat on the outer flange and when installing the thermostat ensure this hole is on the top most point to get all the air out. Bleeding takes seconds.