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

I think I found a picture of the canonical crack in the larger-bore radiator neck. Doing some more research, I find this "potential workaround" which is to bond with JB Weld a metal sleeve, presumably inside the larger of the two most common E39 plastic radiator neck failure points when you replace the radiator.

This thread seems to have decent close-up pictures of the various leaks in the E39 cooling system...

This radiator thread shows a different place where the E39 radiator cracks.

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.

Very nice find!
With this type of leak below, the radiator should still be good to reuse and the nipple can be replaced inexpensively.
The part number to replace that broken nipple is:
17110419132 RADIATOR FITTING $1.00



FYI:

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

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?

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.

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?

Originally Posted by bluebee

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?

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.

The factory radiator can be had for less than $200 for a 540, can't be any more for a 525....I say get oem. The Zionsville is not infallible, I have seen enough posts of seams splitting (usually soon after install) that shows they are hardly perfect. Then you have to pull it back out, send it for repair, then reinstall.

I would order up all the stuff, and have it ready....then drive on till she blows! Mine is a daily driver, so I did my second one at around 130k or so miles (first one was around 55k miles). I replaced everything on the front of the engine, pullies, water pump, fan clutch, thermostat, tensioners, belts, every coolant/heater hose, and of course the radiator, expansion tank and cap. I should be good to 200k+ now...at least on the coolant system.

Bluebee you are kind of at the "between" point...might be worth replacing the water pump, and obviously the belts, fan clutch and radiator and expansion tank, but the hoses should be fine (usually good to 150k according to the tech in Roundel) and pullies and tensioners should be okay too. Swap the rest with your next radiator...if you keep the car that long.

Originally Posted by bluebee

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?

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.

I'm buying a 1997 528i soon and working with the current owner to re-do the cooling system. The car is in excellent condition, but has 177K on it. We found a leak in the cooling system after doing a pressure test. There was a minor leak at the thermostat. So, since the fan shroud and fan were out at that point why not just replace more stuff? Bought four new hoses, thermostat, water pump, fan clutch, thermostat housing and radiator. It's not that much work once you are in there it seems. The radiator was original.

Originally Posted by bluebee

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?

I have a 2002 530i, so I have the same M54, but the larger version. I noticed my thermostat failing with the P0128 CEL code saying something about coolant temperature below thermostat regulating temperature. I'd clear the code, and it would go away for a month or two. It would appear with other codes that I was troubleshooting at the time (I had CCV issues I was taking care of as well.) Because the P0128 would appear with other codes, I just chalked it up to starting the engine and plugging in my OBDII scanner when the engine was cold. I didn't really take the code seriously. Finally, I fixed the CCV problem, and all the codes went away.

A few weeks later, on a trip to Vegas for Christmas, the temperature gauge started to go on the cool side and the CEL came on again (I later has it read and it's the same P0128.) When I was coasting downhill on the I-15 east towards Stateline, the needle actually went into the blue. I got to Vegas safely and searched around Bimmerfest and came to the conclusion my thermostat was starting to go bad, but on the cool side, or jamming open periodically. I guess if it were jamming closed, it would cause everything to overheat. Lately, I realized that it would take my entire 13 mile trip from home to work in the winter mornings for my car to warm up to where the needle was almost in the 12 o'clock position.

I replaced my thermostat ($59.70 at Autohauz AZ) see my thread: http://www.bimmerfest.com/forums/sho...510&highlight=

Immediately after replacing it, my car would warm up to where the needle was in the 12 o'clock position within 2 minutes of driving, and the needle stayed there.

BTW, the thermostat is where you're pointing to in the photo, and it's really easy to replace. The screw with the cross-notches you're asking about is the bleed screw. I followed cn90's coolant system overhaul, using the bleed screw to fill the coolant back up, and it worked, no air pockets!

Good luck.

Originally Posted by nyclad

the thermostat is where you're pointing to in the photo, and it's really easy to replace. The screw with the cross-notches you're asking about is the bleed screw. I followed cn90's coolant system overhaul, using the bleed screw to fill the coolant

Thanks for clarifying the thermostat location; apparently the thermostat is yet another BMW E39 cooling system weak point based on the number of thermostats sold in this thread ...

Here are some DIYs that I'll be reading:
- CN90's BMW E39 Cooling System Overhaul DIY
- CN90's Bimmerfest Cooling System Overhaul Tips & Tricks
- BlackBMWs Zionsville Cooling System Replacement DIY
- CN90's Fan Clutch Nut DIY

Lots of closeup pictures of exploded E39 cooling system parts here.

Well, if there's any consolation as to the longevity of OEM radiators, mine's held up since I drove her out of the dealer's showroom, or 12 yrs now. So, I'm perplexed with these xploding radiators.

Just recently, though, through my fault, I wound up breaking off the nipple by wiggling on it to investigate whether it's broken or not. It is NOW! IT's the #2 part below



I just got that $1 part in and will replace it this weekend. HOpefully, it's not too hard to extract the other half portion of that nipple from the tank. I have a suspicion that I won't be able to extract out, and the only way is to push that part all the way past the radiator tank. IF so, then I will have no choice but to remove the radiator out of the car in order to tilt the tank and draw out the broken part from within. Has anyone replaced this part and if so, how'd you do it?

Originally Posted by bluebee

83916 miles.

Thanks for letting me know where the "classic" break is; I will check where the rubber meets the plastic and write back what I find.

I know it will eventually need replacing (based on this thread and others); however, like others, I also must wonder if the obviously better 600-dollar all-metal radiator is worth it to replace the cheaper plastic radiator (depends on their respective "true" costs).

Not knowing which way I'll go, certainly I would feel safer with the aluminum radiator but we'll have to see if we can find a better price comparison to the OEM or OE (I haven't done that yet as I'm just trying to figure out WHERE to look first to see IF I already have a problem).

PS: I don't need more problems right now, trust me.

...not meaning to be rude - but....

You may want to also go and get a mental health check while you are at it - come on - taking photo's of your mileage while driving at highway speeds. This is how people get killed; no radiator problems then for sure. Hope I am never driving near you

Following up on nyclad who replaced his thermostat following the CN90 DIY, a question came up in that thermostat thread which is relevant here.

Does anyone know the normal operating temperature range of the E39 coolant?

We're not talking startup. We're asking about normal engine temperature.

My assumption is that the coolant is way above the thermostat operating point - so that's why I ask.

After researching normal coolant operating temperature, I opened a separate thread specifically to figure out the actual operation of the thermostat.

Back to the original topic, here's a picture of an E38 radiator with the classic failure.

If mine were to crack, I hope it cracks right there.

I'd move the clamp right up to the edge of the hose, and keep using that radiator

That picture doesn't look right. From what I gather the failure typically occurs right at the neck there so there is nothing to place the hose onto but in that picture it looks like you could do a work-around fairly easy. Bah, I don't plan on even giving my cooling system another thought until over 200k since I had everything replaced at 120k and currently at 130k.

Originally Posted by Mack

the failure typically occurs right at the neck there so there is nothing to place the hose onto

Here's another picture of a failed radiator ...

Would you consider this more of the "classic" failure type?

Originally Posted by bluebee

Here's another picture of a failed radiator ...

Would you consider this more of the "classic" failure type?

LMAO yes from what I've heard the failure happens there quite often.

Originally Posted by Mack

the failure happens there quite often.

OK. Now we have identified the "classic" thing to look for (which is good to know).

I don't seem to have it (yet).

But, it looks like there are quite a few failure points.

For example, here are pictures, apparently, of failures at the various bleeder valves ...

Do you know HOW MANY of these perhaps weak bleeder valves are on the E39?

Originally Posted by bluebee

OK. Now we have identified the "classic" thing to look for (which is good to know).

I don't seem to have it (yet).

But, it looks like there are quite a few failure points.

For example, here are pictures, apparently, of failures at the various bleeder valves ...

Do you know HOW MANY of these perhaps weak bleeder valves are on the E39?

The third picture is a 540 bleeder (there is only one). The other two are from an I6 engine.