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BMW E36 Transmission Coolant Lines Replacement

Pelican Technical Article:

BMW E36 Transmission Coolant Lines Replacement


1-2 hours






Floor jack, four jack stands, safety glasses, metric line wrenches, large drain pan (at least a gallon capacity)

Applicable Models:

BMW E36 3-Series (1992-99)

Parts Required:

Automatic transmission fluid coolant lines, Dexron III auto trans fluid

Performance Gain:

Automatic transmission fluid coolant lines that won't leak

Complementary Modification:

Replace your automatic transmission fluid
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Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6

The transmission fluid change and line replacement was the very first project that I performed on this particular car (my wife's 1992 325is). I purchased the car with a known transmission problem. Basically, when the car was stopped suddenly via the the brakes, and then the accelerator was immediately pressed, the transmission would slip, and then slam into gear, lurching the car forward. Not really a good sign, but I had a strong suspicion that the transmission was low on fluid.

Why did I suspect this A thorough inspection of the car had shown that the seller's wife had smacked the front of the car into a few parking blocks one too many times, and had damaged the underside of the car, right behind the radiator. One of the transmission lines had been damaged, and was leaking a slow, but steady drip of transmission oil. From the looks of the car underneath, I could tell that this had been occurring for quite some time.

BMW claims that their transmissions are "sealed" units. This is a load of BS, as they have very significant and very vulnerable transmission cooling lines that run to the front of the car. It's not uncommon for these lines to become damaged, and start leaking. I found that this particular transmission was several quarts low on fluid, and had been slowly leaking fluid for quite some time. If I hadn't caught the problem, the transmission would have run dry and probably would have been damaged beyond repair. As a result, I recommend that all BMW automatic transmission owners check their fluid often - the alternative could be very expensive.

From underneath the car, you can clearly see the two transmission lines. They have a unique bend to each one - specifically designed to fit around the engine and the front suspension components of the car. Figure 1 shows the pair of lines together. The lines are part hard-line and part rubber line. The rubber-to-metal interface is where most of the leaks come from. To replace the line, start by disconnecting it from the transmission (Figure 2). Use the proper wrench, as there will be quite some resistance to loosening the line. Pull the line away from the transmission when the coupler is loose (Figure 3 and Figure 4). Also make sure that you have a bucket or drip pan underneath the connection, as fluid will immediately start to drip out.

With the rear part of the lines disconnected, now move to the front of the car. (Figure 5) shows how the lines are attached to the front transmission cooler, which is located in front of the engine radiator. Remove the clamp bolt, and you should be able to pull the lines out of the connector. Again, have a pan or bucket underneath to catch the transmission fluid that will inevitably spill out (Figure 6).

The line can then be snaked out and around the suspension for removal. I found that it took me quite a while to figure out how to do this. One of the lines was far easier than the other one. Depending upon which engine you have installed, you may need to remove some suspension components (like the front a-arms) in order to gain enough clearance to maneuver the lines so that they can be removed.

Installation is basically the reverse of removal. Be sure to verify that you have enough fluid in your transmission, as you will have lost some in the process of changing out the lines. See the Pelican Technical Article, Replacing your Automatic Transmission Fluid for more details.

If you would like to see more technical articles like this one, please continue to support Pelican Parts with all your parts needs. If you like what you see here, then please visit our online BMW catalog and help support the collection and creating of new and informative technical articles like this one. Your continued support directly affects the expansion and existence of this site and technical articles like this one. As always, if you have any questions or comments about this helpful article, please drop us a line.

Comments and Suggestions:
ShawninOhio Comments: I have a 2005 745LI E66.
What is the procedure for my car.
Had to rebuild the Trans and the lines where rusted and leaking at the back.
Have everything back in the car but the Trans Cooler Lines.
Thank you in advance
December 10, 2017
  Followup from the Pelican Staff: We don't currently have that tech article. If we get a chance to perform the procedure, we will be sure to document it.

I would suggest you grab a repair manual, you should own one. 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
E36 Comments: Hi, I recently noticed a drop sized red oily leak on the floor. Sometimes it would take around a week with the car parked to notice the drop on the floor making it hard to determine where the leak is coming from. Transmission was recently overhauled as well as its valve body. Transmission was filled with new oil and filter. The car is an E36 325i 1992 with a 5HP18 A5S310Z automatic transmission. What could be the cause of the leak?

September 8, 2016
  Followup from the Pelican Staff: Could be the trans or power steering. I would suggest lifting the vehicle and checking the area of the drip for signs of a leaking component. - Nick at Pelican Parts  
Mike E Comments: Is this possible, please here me out. lets say you get 2 5 gallon buckets one with clean fresh tranny fluid and the other empty disconnect both of these lines one I assume is the hot out and other cooler in, attach some hoses to them. now drop the pan or release the old fluid and re bolt the pan and add fresh fluid, here's the real question though start the car and go through the gears a few seconds in each there by doing a real 100 percent fluid change torque converter, transmission and lines, what are your thoughts?
August 13, 2015
  Followup from the Pelican Staff: Will not work. Transmission pressure will spray fluid everywhere. Needs to be sealed system that can handle line pressure. - Nick at Pelican Parts  
Morales Comments: What am I looking to pay on labor for this job?
August 29, 2014
  Followup from the Pelican Staff: I wouldn't know. I would call around to a few shops and ask for estimates. - Nick at Pelican Parts  
beemerwagoneer Comments: I got a used trans from a friend the front female receptacle for the transline is reemed out could not get the line to turn and thread in now it has striped out is there a way that I can tap and dye this to fix the threads and what size is that nipple that feeds into the trans so that I can get the right size tap any help would be appreciated I don't want to have to remove the trans again there is enough space to work without removing it again please any help would be appreciated
May 19, 2014
  Followup from the Pelican Staff: I don't know the size. You can measure it using a thread gauge available at any hardware store. - Nick at Pelican Parts  
R111S Comments: 1997 BMW 318ti - These lines were somewhat difficult to remove/install. I cut open a 19mm Box-end Wrench used a Diamond Saw in order to unthread/rethread the Lines where they connect to the Transmission – A 19mm Crow-Foot was practically useless. Fishing the lines through the maze of frontend components was a challenge – had to come from the back, long line first, then the short line...rotating screwing? the lines helped. I also had to remove a Cross-Bar to allow the Lines to drop out.
March 23, 2014
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
FixitRod Comments: How many o-rings are needed to prevent leaks at AT line to transmission oil cooler/radiator fig. 5. Car leaked bad after reassembly as O rings were damaged. I found parts of 2 but your ad says ..."needs 4". How would install? How many actually?
March 2, 2014
  Followup from the Pelican Staff: I believe it is two per line. A total of four. - Nick at Pelican Parts  
RF Comments: I have a bmw335I 2007 with a transmission cooler hose, will i have to remove any motor mounts or suspensions parts to remove the lines?
February 21, 2014
  Followup from the Pelican Staff: You may have to lower the transmission or jack the engine. I forget exactly what this model requires for the job. - Nick at Pelican Parts  
Old_318 Comments: Where can I purchase the 'O' rings for the ends of the transmission line? Or do you know the size or part reference number? Thanks.
December 2, 2013
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799. They can help you find the right part. - Nick at Pelican Parts  
EUROHB Comments: What kind of tranny fluid do I use on the 318ti auto?
October 18, 2013
  Followup from the Pelican Staff: Not sure what year your vehicle you have is, but the fluid for your vehicle should be here: - Nick at Pelican Parts
bimmergirl1 Comments: Can someone Please please tell me which way to turn the bolts that connect the transmission lines?? I have a 1984 733i. I have to replace them and have the new lines but the bolts are so hard to turn and I am even wondering if I am turning them the correct way or not. Plus I am having trouble getting the car high enough to even use a cheater bar to help. Can someone please help me here? Thank you in advance!!!
September 28, 2013
  Followup from the Pelican Staff: The bolts should be standard thread, turn to the left to loosen, you might have a problem with rust, try using WD-40, spray it on the rusted bolt and try to loosen it, turn it back and forth until it frees itself up.
- Nick at Pelican Parts
speedy 530i Comments: by me removing the alternator and the power steering pump does that make it much easier to remove the trans oil cooler lines or is there a way to fish it out with out removing the bracket for the motor mount or the alternator , power steering pump and will i have to refill my trany with more atf fluid with doing this project
September 8, 2013
  Followup from the Pelican Staff: There is a bracket that holds the lines in place under the p/s pump, you are going to have to remove it and the alt, and the motor mount bracket on the drivers side, you are also going to have to top off the trans fluid when you are done.
- Nick at Pelican Parts
speedy 530i Comments: i have a 2001 530i my trans oil cooler lines are leaking will i have to remove any motor mounts or suspensions parts to remove the lines and what tools do you recommend
September 7, 2013
  Followup from the Pelican Staff: You are going to have to remove the alternator, power steering pump, and the bracket for the drivers side motor mount. You can leave the lines on the pump it just needs to be moved out of the way to get to the bracket that holds the trans lines. standard hand tools will get the job done.
- Nick at Pelican Parts
beasley Comments: i have a 2000 bmw 328ci. I am replacing the tranny cooler lines and don't know how to put the new ones in. Its seems that i have to take part of the suspension out and the engine mount. please help... what do i do?
February 23, 2013
  Followup from the Pelican Staff: You will have to disconnect both ends of the lines, then remve the lines from the mounting brackets. Once lines are free, you have to jack the left side of the engine, remove an engine mount nut, jack engine, then remove lines from vehicle. - Nick at Pelican Parts  
oddone Comments: in figure 2 can some one tell me the size? thix
December 5, 2011
  Followup from the Pelican Staff: If I remember correctly, it is a 16mm. - Nick at Pelican Parts  
wisso Comments: i resently bouth a bmw 318 ti 97 with 72,000 original miles
iam a toyota fan old school, did not now what to espect as i do all my mechanical work myself exe elec but u guys made a world of diference thanks for the inf and advice.
September 2, 2011
  Followup from the Pelican Staff:
Thanks for the feedback. Glad we could help. - Nick at Pelican Parts
Travis Comments: installed a new line today, the shorter one and i made sure everything lined up but the male connecter didnt wanna thread in. i stopped as it was getting dark, no need to rush on a expensive transmission. is there any trick to help make sure im 100% lined up because it will catch but tighten right away and it acted like it was goin to pop a thread so i backed it out. any help or tricks?
August 26, 2011
  Followup from the Pelican Staff: What i find helps is if you leave the line loose on both ends, then start the thread. Once the thread is started you can secure the line place. It can be tough the start it if it is at even the slightest angle. - Nick at Pelican Parts  
Les Comments: Need to re install male lines to the new atf cooler I installed on my 95 bmw 325is what size o-rings should I buy and where can I find them. Should the o-rings fit be snug over the male lines and slide up to the collar?
December 29, 2010
  Followup from the Pelican Staff: The O-ring should fit on the end, as the old ones were. I am not sure of the size, but if you give our parts specialists a call at 1-888-280-7799. They can help you find the right O-ring. - Nick at Pelican Parts  
Sean Comments: I have a '97 328. I might be missing something like an access panel in the transmission tunnel, BUT it appears the trans must be unbolted from the engine and lowered to get to one of the lines.
September 27, 2010
  Followup from the Pelican Staff: The trans doesn't have to be removed. It is however a tight fit. If you are stuck, try placing a jack under the trans and loosening the trans mount just enough to sneak the lines out.- Nick at Pelican Parts  
jeanmichel_d Comments: I would like to add a comment about the "o" rings at the end of the transmission lines that require replacement if those lines are disconnected..
September 17, 2010
  Followup from the Pelican Staff:
Thanks for the additional Info. We appreciate it.
- Nick at Pelican Parts

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