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Where exactly do we look on the E39 radiator for telltale cracks?

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182K views 238 replies 59 participants last post by  energizedmortal  
#1 · (Edited)

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#2 ·
On my '02 525, the slow leak was coming from the driver's side of the radiator. Many posts say look at the top of the radiator on the driver's side where the overflow/recirculate hose connects. This area often cracks. Your picture above in the center is exactly the weak area. In my case, all was dry and uncracked at the circulator hose and at the main coolant hose connection. I just had a slow drip coming down the driver's side of the radiator and onto the splash pan underneath. I believe my radiator was simply failing on the side seam after 135k miles and 7 years. The replacement of the radiator, water pump, and hoses was not hard.
 
#6 ·
Neversaynever said:
On my '02 525, the slow leak was coming from the driver's side of the radiator. Many posts say look at the top of the radiator on the driver's side where the overflow/recirculate hose connects.
Click to expand...
Mine's leaking right there. This plastic nipple looks like it's clipped/snap fitted into the top of the radiator. Is this part replaceable? Or is a new radiator the only way that comes with a new nipple?
 
#8 ·
and here i was thinking that I was close to being done with all my repairs :cry: mine is starting to show similar wear..

The other day mine decided to spit coolant all over that side of the engine bay..
 
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#4 ·
^^^^^ yup check where ever there is a hose connection into the radiator.
 
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#7 ·
Best place to look is your odometer. If it's over 80k then you're on borrowed time. LOL all seriousness aside Bluebee I went to 120k before I did my cooling overhaul with no issues. My thermostat did go bad at about 85k miles though and I replaced it quickly. How many miles you got on her?
 
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#10 · (Edited)
1+!!!

Bluebee, the classic crack is exactly where the UPPER Hose joins the radiator.
This is the area where the plastic neck (the hose attaches here) joins the plastic side tank.
The problem is: it may leak slowly, giving you time to fix, or it can erupt like a volcano with no warning.

Some people have crack radiator at 60K, some runs all the way up to 160K or so.
I am like Mack, stay on the conservatibve side, and replace the rad at 80-100K, considering that an overheated engine will cost you some $4-5K bones!
 
#9 ·
I'm at 62k and had a leak right around the water pump, so I replaced that and the thermostat preventively. I went over the radiator carefully and did not see signs of leaking, but I did replace the upper hose cause it was brittle though not leaking. But I'm planning on/assuming I'll have to replace the rad w/i a year. or around 70k miles. Not sure which rad I'll put in, but it won't be OEM.
 
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#11 ·
I was saying the same for the longest. But an OEM rad only cost me $146 to the door. A Zionsville would've cost around $600. I did the math, it didn't work. I went with OEM/Behr.

cn90 said:
1+!!!

Bluebee, the classic crack is exactly where the UPPER Hose joins the radiator.
This is the area where the plastic neck (the hose attaches here) joins the plastic side tank.
The problem is: it may leak slowly, giving you time to fix, or it can erupt like a volcano with no warning.

Some people have crack radiator at 60K, some runs all the way up to 160K or so.
I am like Mack, stay on the conservatibve side, and replace the rad at 80-100K, considering that an overheated engine will cost you some $4-5K bones!
Click to expand...
Agree whole heartedly bro. Plus I didn't want to end up stranded out somewhere and have to shell out mad ca$h to get it fixed on the road if I was too far away from home. :thumbup:
 
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#13 ·
Hmm, I could have sworn I started a thread a year or so back to ask at what mileage all E39 owners experienced cooling failure or replaced proactively before failure. I can't seem to locate it though. Still, I think many will agree that if you're above 80k on your original radiator, expansion tank etc. it's time for an overhaul. I suspicion 525's are not nearly as hard on the cooling systems as the others because I made it to 120k with no major failures and confirmed I still had the stock rad but at that point I was getting nervous and decided to go ahead and put in all new hoses, expansion tank, rad and water pump because I didn't want to end up stranded somewhere. Anyways goodluck with what you decide!
 
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#16 ·
Mack said:
many will agree that if you're above 80k on your original radiator, expansion tank etc. it's time for an overhaul.
Click to expand...
I'm above 80K so I'm worried but I'm still a bit confused. Did I mark the right spot below on the composite diagram where to look for the classic crack?

(If not, I supplied a blank composite for someone to correct where I err.)

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#14 · (Edited)
I don't think radiator failure can be related to a specific mileage. It seems to be caused by repeated heat cycles. After many, many times of the plastic being heated and cooled and flexing with internal pressure, it will become brittle and crack. Bad motor mounts will exacerbate the flexing. The additional heat of a V8 will cause it to happen a bit earlier. Cracks are common at the upper and lower hose connections, but can occur anywhere on the plastic, including the side seams. The expansion tank, thermostat housing, and all other plastic cooling system parts may also be the source of failures. Many, if not most, cooling system failures are catastrophic, requiring the vehicle to be immediately shut down and towed for repair. Failure to do so can result in significant engine damage, particularly in the I6 cars. Far too often the first sign of a crack is complete failure.

Considering the risk, most here think it prudent to refurbish the cooling system at 60-80k miles, although my radiator failed at about 50k. Desert heats and a V8 engine appear to speed the process. I am now considering Evans NPG+ in a zero pressure system. It is a lot cheaper than a Zionville radiator.
 
#15 ·
I'd also add that many if not most of us do the majority of our driving in the nicer/warmer months, so more o' dem miles are coming when the temps are higher, putting more stress on the rad. All you daily drivers need only worry about the CCV freezing and cracking! Haw haw haw!
 
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#18 ·
Pic attached. For what it's worth, just replace the radiator and call it a day. Don;t worry about hoses or anything else. Not a bad job if you've had the fan off previously.
And BTW, how do you post a picture full size? I only know how to post the thumbnail.
 

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#21 ·
I totally disagree with this. IMHO you'd be crazy to change the rad and not do the hoses. No offense but that's what I'd call a half-assed job.

bluebee said:
I'm above 80K so I'm worried but I'm still a bit confused. Did I mark the right spot below on the composite diagram where to look for the classic crack?

(If not, I supplied a blank composite for someone to correct where I err.)

Image
Click to expand...
I'll have to defer to others here who have experienced rad failures but from what I recall many have experienced cracks right at the neck there. Some even after changing busted hoses just from the jockeying off and on with the new ones there at the neck after it has become brittle but again this is only what I've seen hearsay as I replaced all my stuff proactively not wanting to experience the nightmares that many here have seen. As always enjoy your thoroughness and goodluck Bluebee!
 
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#19 ·
Mine split just below the upper hose connection nipple on the plastic end cap at a spot close to where Bluebee pointed to in the diagram. It happened on the way home after picking it up from the dealer. Luckily I was near an exit on interstate 95 and was able to get it off at the exit and shut down. It had 76K on it when I took delivery. One thing compounded the problem, the pixels on the cluster were so bad that I couldn't read the warning of low coolant. When the high temp alarm came in I could just barely make out the "TEMP" part and only then knew exactly what was happening. Luckily I was within 500 ft. of the upcoming exit and could get off and shut down quickly before any serious damage happened. The dealer towed and replaced the radiator as MA has a mandatory 3 mos/3.6k warranty for all used vehicles under 90k total miles. BTW, I've since had the cluster replaced under the BMWUSA goodwill program.
 
#20 ·
Bluebee, the radiator is sometimes but not always the first thing to go. My grandfather had a hose blow up, followed 2 weeks later by his expansion tank spontaneously blowing out. I've had a leaky... something... under my expansion tank that leaks when it's <0°C, but it's been that way for 10k km. (fingers crossed) The weather sucks, so I'm waiting until later this year (if I'm still driving it) but I will be doing the whole cooling system. No f*cking around is what I've learned (so I'm f*cking around pushing my luck to 100k miles)
 
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#22 ·
I have to agree with everyone else. Mine went at 80k exactly. But started with the overflow tank, then thermostat with housing and finally the radiator blew at the upper hose connection. I replaced all hoses and pump since everything else was new. Like previous posters said, you're on borrowed time now.
 
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#25 ·
I defer to you Mack on the hoses.. I did the entire refresh as CN90 suggested including hoses and thermostat and expansion tank etc. I just didn't think the t-stat or hoses needed replacement on my car and I had 137k miles. And with BlueBee having a meer 80k, I thought radiator alone (and maybe expansion tank) would leave him in good shape. But honestly, what do I know....
 
#26 · (Edited)

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#27 ·

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#29 ·
On my 2000 528i, there were two hairline cracks in the cooling system. Both were on plastics. I saw faintly the telltale sign, which is white line, apparently from the coolant. The cracks were both on the hot side. One was on the upper radiator hose (hot), and the other on the radiator where the upper radiator hose meets the radiator.
 
#31 ·
While I think we've identified the canonical location for BMW E39 coolant leaks, as noted by others, chasing a coolant leak might also lead to the "water pump" or to the "valley pan gasket".

2002 M5: Chasing a Coolant Leak - Part One
1999 740iL: Water Pump Coolant Leak
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#32 ·
I am not totally sure but I don't think I found any coolant leaks in my radiator (see pics below).

At 85K miles, now is not a good time for me (relationships and job woes galore), so, would it be ok to postpone the radiator fix for a while you think?

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#37 ·
It is all a crap shoot, like Vegas....it looks fine now, but who can say it doesn't let go tomorrow? Mine went at 55k or there about (maybe sooner), and I did the maintenance to a tee, including having a full flush only 6k miles prior. It is all about heat cycles, and stresses from things like bad engine mounts, etc. My maintenance was good, engine mounts were fine, and yet it split on the side and started leaking...go figure. :(
 
owns 2001 BMW 540 M-Sport
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#33 ·
Do you have Triple A? All BS aside though I made it to 120k before replacing mine and it was still good to go at the time. I suspect you can safely postpone it since you also have a 2002 525i for at least another 20k if you really want to. Can't remember if I read whether you replaced your thermostat or not though. Mine went at around 80/85k and I changed it pronto.
 
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#34 ·
Thermostat, as far as I know, is original. I wouldn't know how to tell if it were bad. I guess it's easy enough to replace (I hope) but I guess if it were stuck open not much would happen in the temperatures I get here in sunny California - but if it were stuck closed, seems to me the engine would overheat.

Do we recommend prophylactic replacement of the thermostat? Is it easy?

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#35 ·
Well mine tripped the CEL when it went bad. I've stated this before but I believe going too long on a faulty thermostat is the cause for many a cooling system breakdown. Again that's just my theory, mostly because mine went bad, replaced and then I went on to 120k with no further cooling system issues. I suggest keeping a close eye on it if nothing else and make sure you have quick access to parts at a good price. You don't want to end up broken down with only a dealer or shady indy as your options where they'll charge you 10x what it would normally cost.
 
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