Bleeding Radiator - Perhaps THIS is the problem.

[Manolito]

Neither of my '97 328s seems to bleed properly, and both of them have chronic "Low Coolant" messages in the computer.

I pulled the radiator out of one of them on my way in to replace the original water pump, and I noticed a rattle in the overflow reservoir.

I shook out a couple of pieces of broken plastic. That can't be good.

Ordered a new reservoir. Took my Dremel tool and split open the old one to find out what failed inside.



I still don't fully understand how water can flow out of the bleed screw hole when the reservoir level is 2-3 inches lower than that hole, but it must have to do with the stream of hot water coming in through the little 1/4" hose. That hot water blast also seems to attack the plastic.

However the bleed works, I am pretty sure that having a chunk missing from the split tube that goes from the bleed screw down to the bottom of the reservoir will have a deleterious effect on the bleeding procedure.

By the way, this failure was not visible through the fill hole. I rotated that tube around so that I could photograph the failed section. It was facing the side of the tank originally.

[Jeron]

I've seem that theorized before and I'm pretty sure that the broken internals is the most common cause of "Low Coolant" message. I have the same issue, broken bits and all.

[coolbear1]

You may be on to something. I have fought mine for years. Even after replacing the radiator and the coolant sensor I had to bleed it, burp it, and give it mouth to mouth ( LOL) before it would stay at the top. I never looked at, or suspected the expansion tank.
Please, let us know the outcome.

[Duke4AZ]

Da#*! Those look an awful lot like the bits I just shook out of my expansion reservoir when I was putting my 98 328i back together (reference timing chain cover replacement thread). After reading this post I got curious because my low coolant light comes on quite often. Besides a lot of sediment I managed to extract a couple of small pieces of curved plastic that look suspiciously like the wall of the internal bleed tubing. Just one more $75 to throw on top of the new parts pile. I suppose I could buy a used one but based on what I am reading, there is no telling how long that would last or if were even sound to start with.

Good tech post. It helped me to avoid reinstalling a bad part that I did not know was bad.

Duke.

[Duke4AZ]

One more little ditty on this subject. While it is not always possible to see if and where a breach may have occurred along the length of the tube, it is possible to detect the problem. What I did was to take a long thin piece of wire with a short hook on the end. I ran the tip of the hook down the length of the tube and "felt" the wall of the tube. you can feel where the wall has been broken if there is material missing. You will have to experiment with the shape of the hook at the end of the wire to feel the different sides of the tube, but it is possible to get it all the way around the back side of the tube. Once you find a discontinuity in the wall of the tube, mark the depth of the wire into the expansion chamber and holding that up to the outside of the chamber you can determine just where the breach is located.

Cutting it open with a Dremal tool works too, but it takes a lot of JBWeld to glue the expansion chamber back together.

[Dave at Pelican Parts]

Please ignore the stupid spammer. He's been banned, and hopefully his messages will be gone soon.

--DD

[coolbear1]

Thank you Dave,
Checked out photo's, nice mid engine by the way.

[Manolito]

I will report back after assembling the car. I have no hurry to finish that project as my daughter won't be back and need the car until after the school year ends. The car is sitting in my garage partially disassembled with a sheet over it.

[Duke4AZ]

Originally Posted by Manolito

Neither of my '97 328s seems to bleed properly, and both of them have chronic "Low Coolant" messages in the computer.

I am a believer.

Long story short, for various reasons I replaced the radiator and expansion tank in my 98 238i e36 (159K miles) this weekend. When I pulled the tank I was rewarded with various plastic bits, not dissimilar to those you show in your posting. I have not dissected the tank, but posted a couple of pics. One clearly shows that the large baffle through the middle of the tank is both cracked and missing large chunks of material. So based on your previous post, I can guess this should have not be much of a surprise.

One question I have to ask though is the coolant/antifreeze that you were using and how often do you change the stuff? I am currently running Prestone at a 50/50 mixture ratio. However, because of a water pump and head gasket replacement recently performed, the cooling system is completely new in front of the firewall, I am thinking about flushing the system again and going with the BMW fluid. Any experience with that vs the domestic stuff?

Another question, or maybe comment is that darned block plug. The coolant drain plug in the block is located right on top of one of the O2 sensors. To get the plug out I have to remove the sensor and then have to tape up the hole so I don't fill the exhaust system with coolant. What is up with that? I just know I am going to take a shower when I pull that plug.

Well, just thought I would put some feedback to your previous post as it did give me a heads up on an eventual failure.

[Manolito]

With regard to antifreeze, that turns out to be a complicated subject with a lot of conflicting opinions posted on the Web.

My experience was that I was using Preston 5/50 long life antifreeze in my old Volvos, so I put it in my first '97 328. It seemed to satisfy all the criteria in the owner's manual - non-nitrate, non-silicate.

A year or so later, the original radiator failed. No big surprise there, it was seven years old and the top neck blew off - the usual failure mode.

Replaced radiator with a new Nissen radiator. Filled with fresh 5/50.

Less than two years later, both seals that seal the plastic end caps to the aluminum center were leaking. I first blamed the radiator and ordered a Behr radiator to replace it. However, after reading some reviews, I concluded that the coolant had probably attacked the seals. I filled it with BMW branded coolant, and I have used BMW coolant in all three of my BMWs since.

BMW coolant is very expensive, so I would be interested in using something else if I could trust it.