Overheating issues, Help needed and appreciated.

[iamjohn2407]

My '86 E24 has been having horrible overheating issues the last few years. Doesn't help that I currently live in Vegas, but I don't think that's all of the problem.

As for what I've done, I've replaced the pump, replaced the thermostat (with a slightly lower temp), replaced the radiator, flushed the system, carefully blocked off the heater core in case it was causing issues, from what I can tell I blead the system just fine (even elevated the front end and let it run for around 20min one day to see if it would bleed it a little better by recommendations online) I've custom made a dual electric fan and shroud, installed an aftermarket temp gauge that is set midway in the return from the radiator. And of course checked that it wasn't leaking into the oil or leaking oil bad to begin with.

I'm at a loss for why its doing this. Just this afternoon I went to get groceries a few miles away, mild traffic, and by the time I got home it was sitting at 100c. Any advice welcome, or if you happen to be local the better (but from what I can see most here just like BMWs because of the money status symbol and not because they are good, typically, cars).

Thanks for the help.

[Tnarkowicz]

Do you still have the original main fan? If so, have you checked the viscous coupling? This is a common failure item, and presents as rising temp at low speeds, eg stop/start traffic when airflow into the engine bay is limited.

[Nullified]

Is the thermostat actually opening? I've had the same problem and on my car the problem was that the thermostat couldn't own due to being physically wrong. The one it replaced had a broken part, the replacement had a to large disc. It couldn't move into the housing to open up.

[EuroGeorge]

I always pop the new thermostat in a pan of water and heat it up using a thermometer to make sure it does open at the indicated temp (72 or 81C). If it does not I return it. An old school test for the fan clutch is to take a rolled up magazine or some rolled newspaper and once the engine has reached normal operating temp, stick it in the rear of the fan blade. If you can stop the fan from spinning, your clutch is toast. If the fan tries to shred the paper, it's good. PLEASE be careful with this technique.

[iamjohn2407]

No I do not, as I said I have a dual electric fan setup, I replaced the stock fan a couple years ago when I replaced the water pump.

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That seems like a good way to damage the fan if not end up with more garbage in your engine bay, however I do not have the clutch fan installed any longer, I replaced it with a dual electric fan setup so I know the fans are on when I turn them on. As for the thermostat I probably should have checked that when I had it all apart last.

Side note I've also pressure checked the system a while back to make sure it wasn't having issues there either and to help with the bleeding of it. And it does fine when it is cooler out, it really only starts having issues when it start getting above like 30c outside, in the winter the car never goes much above 84c.

[sienayr]

So how do you know that your custom fan setup is pushing enough air at the right time? Getting hold of an original fan with a good clutch to test would eliminate that as a problem, since it sounds like you've eliminated many other possible problem sources.

...installed an aftermarket temp gauge that is set midway in the return from the radiator.

Maybe something else to reverse back to OE if you can and test (I'm thinking you meant temp sensor, not gauge?)

[RSheiman]

Two things:

Bleed it again

Did you drain the block? There is so much crap in there, if blocked up, you will overheat despite all you have done.

[iamjohn2407]

I didn't drain the block because even after looking it up I still wasn't sure where the block drain was, never could find a good picture or decent explanation of where the drain bolt is located and there are more than a few bolts down there. However I did flush it with one of those system flush cleaner things multiple times (8 times I think running it between for around 10 min, and even taking it out for a drive mid way through to make sure it was circulating enough, oh and I left out the thermostat while I was doing that also to ensure it was flowing fully), until it was coming out clear then filled back with coolant. And I've tried bleeding it multiple times as well including lifting the front off the ground about a foot and letting it run like that till the system was under pressure and actually pushed out some excess coolant from the tank. I've even drilled a small hole in the thermostat because it didn't have one of those little bleeder one (as suggested in another thread) to help let any trapped air out and made sure that it was facing top. Though I might raise it up again and do another bleed just in case.

They really didn't seem to make the coolant system in this car very well, the bleeder isn't at the high point of the system and the stock radiator doesn't have a fill port in it so its a pain knowing if you've got it full or not. And working on it isn't all too easy as I'm doing everything in an apartment parking lot so I'm slightly limited as to what all I can do.

[bmw6fan]

Try it without the thermostat and see how that goes at this point!

[Nullified]

That's what I did too after I found out it overheated, I drove without it until the correct part was delivered.

[iamjohn2407]

I've read both good and bad for doing this, mostly that the constant high flow can actually cause it to not get enough time to cool off the fluid especially in hot locations such as where I currently live. If I take the thermostat out to check it I might try this for a few days though to see if it does anything different.

[slownrusty]

Curious as to what electric fans you have, what is their CFM? The reason I ask is that several of these aftermarket electric fans do not come with a shroud or come with a generic shroud that is in efficient and may not channel the air effectively through your radiator. Do you have pullers or pushers? The shroud seems simple and is often overlooked but is also worth looking into as it play a very important role in the colling efficency. Also how are your electric fans triggered? Is it through a thermocouple in the raditor hose or through the fins? I've installing aftermarket electric fans for over 20 years on various cars so know my way around them and have done a fair bit of fabrication to make mounts and shrouds that actually work. I'm here to assist you.

[Nullified]

In my case the choice was:
* overheating and fucking the head gasket and warping the top of the engine, or
* running a too low temperature

I was 115km away from home so I chose to take the thermostat out and drive home.

[iamjohn2407]

If you look at my projects page you can see what I made for the shroud and how they it all looks mounted in the car. They are pull (made sure they were proper direction when I bought them), I can't remember the CFM but was fairly certain it was listed as plenty compared to the stock fan and others (besides the super expensive high flow fans). They are currently triggered with a switch I have mounted in the cabin. I have a Dakota digital fan controller I haven't hooked up yet to run them when the car is working properly, and the AUX fans are actually running full all the time because of bad wiring so I just wired it to run high all the time when the car is on for now till I also wire it to the Dakota digital switch.

Part of the issue with the shroud was the amount of room for mounting. I will say this though, when only the AUX fan is on it forces the air though directed enough to actually push the other fans to spin.

I don't mind making my own stuff, quite enjoy it actually, but am somewhat limited by location (living in an apartment is restricting) and currently cost.

[slownrusty]

I cannot see or not sure how to access your projects page. The fans really need to be triggered by a thermocouple and not a manual cabin switch,

[iamjohn2407]

They really just need to be on to help cool the coolant off, so long they are turned on before it starts over heating it should be no different if I'm doing it or a thermocouple (being just another switch) is since its the same effect either way. As for allowing the car to heat up I live in Vegas there is never an issue with the engine getting hot enough, and I tend to turn them on a few seconds after I start the car up so they are always running just in case and so long as the thermostat is working properly (it seems to do so when it isn't 90*f or above outside as in the winter it never goes above like 84c in the loop) then having them running early shouldn't be an issue.

The pictures are in the albums, they are on the left hand side of profiles from what I can see.

[1986series6]

So, my question is did you rely on the dash temp gauge to determine overheating or did you measure
with a temp gun the upper and lower rad hoses, thermostat housing, upper and lower temps of radiator,
turn on heater valve -measure temp there.

You have to diagnosis the exact cause or you may not solve the problem. My 86 I've had for 31 years never had a
temp problem, just meaning that it can give good service over the years . The newspaper test has been working fine for years, how would you test the fan clutch or would you
buy a new one--never knowing if it was the problem. Upgrading a system I agree with, redesigning a system may not always be for the better.

Just my $.02

Bob V

[Anejo]

"I've custom made a dual electric fan and shroud, installed an aftermarket temp gauge that is set midway in the return from the radiator."

If your temp sensor is situated at the radiator outlet side, EI, cool side, the fans will be actuated way too late. They should be switched/monitored from the hot side.

In order to rule out a crack or a gasket issue, have you done a coolant hydrocarbon test? Do not run this car without a thermostat. You can drill two 1/8 holes across from one another in the thermostat valve. The fans sound like a potential problem however I have not seen your setup. Electric fan needs to be switched in two stages and should be on anytime the AC is on providing sufficient CFM. You cannot monitor the temp to switch manually fast enough through the gauge. I was a factory tech when these cars where new. I was in Southern Cal and serviced cars from Phoenix and Palm Springs quite often. The factory setup worked fine then and should now. Yes, you have to raise the car WAYY up to get all the air out. Best to leave it untapped overnight while jacked up and add coolant through the bleeder when stone cold, you can make a brake bleeder tool to do this. Sometimes running for a while with the smallest hose atop the radiator disconnected will yield air bubbles as well. Do this first and before raising the car. Some cars are more finicky than others. Be sure to have the heater on full heat wide open throughout this process. If the problem persists, repeat. ALWAYS test new thermostats as mentioned in a pot of water and watch for smooth, even, complete, opening, not cocked, etc. There was a time when 20% would fail this test when new. Hope this helps, Steve

[DesktopDave]

I like the work you did on those fans. The radiator is properly shrouded, those dual fans should flow enough air to cool the car down from what I can see. I'm also tempted to agree that your cabin switch should be more or less just as good as a thermocouple. Anejo is right about the temp, these cars store a lot of heat in the block before you see it in a radiator-mounted sensor. The fans will take a while to pull heat out of the system at high ambient temps, especially in low humidity situations. I'm also betting you're using the Dakota digital temp readout since we all know the stock temp gauge isn't very accurate.

I've seen a lot of failing pressure caps over the years. My cheap HF pressure tester doesn't have a cap adapter, and a new part is pretty cheap insurance. I usually just buy a new OEM BMW cap while I'm tracking down BMW's traditional cooling system problems. They are easily overlooked and can fail in in the same pattern as you describe.

I was looking at your pics of the coolant neck, did you just install new crush washers? I'm only asking because it looks a little damp under the temp gauge sender & CLT temp sensor. Both also have a little corrosion, that's unusual in my experience. Is it possible that you have a high-temp pressure leak at the switches or coolant neck gasket? I agree with you about BMWs cooling systems, they are over-stressed and under-built.

Here's a direct link to your project pics I pulled from your profile: https://www.bimmerforums.com/forum/a...p?albumid=5742

The engine block drain is a large 17mm bolt on the rear passenger side of the block. Feel around under the #6 exhaust manifold pipe between the bellhousing flange and the oil drain passage. It'll be at the bottom of the cooling jacket, just above the "bulge" of the lower crankcase.

M30 Coolant Drain Plug.jpg

[iamjohn2407]

My apologies for taking so long to respond, THANK YOU very much for the picture of the block drain!!! I am planning on doing another flush soon to try to rule out the "coolant flush cleaner" leaving behind some kind of stuff causing bubbles. And while I'm at it I'll test the thermostats (I still have the old one I replaced that is the higher temp one, haven't found anything saying the 72* thermostat was bad for overheating? but might put back in the stock one to rule out issues as well). My other concern is of course proper bleeding of the system, I'm slightly limited as to my ability to do so, I have basic jack stands and a hydraulic floor jack but can only raise it so far up, and well I'm still not sure if I'm doing that properly. It is odd that the air drain is actually not the highest point though it seems when raised, why couldn't they have just put the fill type radiators to make it easy?

I had one of those silly temp gauge pressure caps and changed it back to a standard one, I think it is a 16 bar one though so I might try to get a stock one of those as well since I think the stock is 13 bar. I do know it allows water out since it releases some when it is overfilled. From my own reading I had thought that I slightly higher pressure cap would be better to allow the system to not boil off as quickly. Another thought on those lines, what coolant is better for raising the boiling point the green stuff or the orange stuff? I know the book calls for the orange stuff (sorry can't be bothered to look up the technical names right now), but the car had the green stuff in it when I did the first change (that could have been part of the problem if the last person mixed them, but it did fine for a few years). The pressure tester I used didn't have the one for that tank, BUT it has a universal one that seemed to work (I borrowed the kit from AutoZone), and it held at around 16 bar just fine for a few minutes before I released it.

I have replaced all the sensors, and with that the washers, and there was some corrosion around the hoses, but I cleaned that off the last time I had the hoses off to ensure proper sealing. And unless its very minute it doesn't seem to be leaking any fluid. Though I guess a high pressure leak would possibly effect the boiling temp and then cause over heating as well?

Thank you as well, it wasn't the most professional job I could have done with the fans and shroud... but I live in an apartment with no garage so doing such on my back porch isn't the most ideal conditions. I'm considering hitting the junk yard as well to find a larger alt fan from some larger SUV or something to replace mine, couldn't hurt I don't think if there is space enough. I'm not using a Dakota digital temp gauge, but I do have a separate temp sensor installed in a housing midway between the return pipe from the radiator and a digital gauge in the car (I assumed if the "cooled" fluid was too hot the rest probably was as well), the stock sensor won't run the dash gauge AND the other one as well when spliced. As for the switch I typically have the fans running all the time so its not a matter of timing, living in Vegas I assume its plenty warm to not worry about the engine being too cold ever.

I was also wondering if the car didn't respond well to synthetic oil, I know my '82 7 series HATED synthetic oil, but my last few oil changes I put in synthetic (royal purple the last time), but i'm not certain if the heat conduction properties of the synthetic are different than normal oil. I might also do the oil change along with the flush and switch back to test that out, probably won't hurt anyhow.

As much as I would love to assume that BMW did their research for the vast markets and climates of North America, they are still cars built mostly for the European market and being so probably not assumed to have as many over heating issues as you would say in the stupidly over hot climate of Nevada or similar places.

Thank you for your response again, That was helpful. I am trying to do all this in not only an aggravating place (my apartment parking lot), but also on a limited budget right now so its even more stressful for me because I can't really afford the issues.

[iamjohn2407]

I have not done, nor do I know how to do a hydrocarbon test, I have only looked at the fluid and not seen any in either but I guess that isn't fully accurate by any means.
I only drilled on hole at the top point of the thermostat, and yes I should have tested the new one before putting it in, it does seem to have no issues in the colder weather though so I think its not the thermostat (though will be testing when I do another flush soon).
I don't run the AC ever, actually have it disconnected fully, and my heater is bypassed (blocked on both sides not connected as to avoid that hot coolant loop that might cause issues as well) so I can't run it but shouldn't matter if there is no fluid flowing into it.
I could be something simple or something caused over the years that age has done to the car, you didn't mention if you've looked at any of them recently maybe long term they have problems, or I just happen to have bought one that decided to have unusual problems.
I unfortunately can't leave it up overnight, would love to have that ability, but living in an apartment they get pissy at doing any work let alone if its left overnight looking like that, how high up would be enough? I put it up on jack stands at high as my floor jack will allow and its already on a slight incline because of the parking lot. Just to be sure you say TO run it with the small hose off for a little bit?

I might just have very bad luck with vehicles as I've had more than my fair share when it comes to cars having issues. If I had the money I might even consider buying a factory new car just to attempt to avoid them, but I don't...

Thanks for the help.

[DesktopDave]

Ramps should be more than enough. I never needed more than a small incline to bleed my cars properly, and I live on a really steep hill, LOL. The blue BMW coolant is best, only slightly overpriced. I'm pretty sure Zerex G48 is very similar, but I've never seen it in a local store. I will substitute Zerex G05 when I can find it, since it's phosphate-free and compatible with aluminum radiators & iron blocks. A few places recently started to carry Pentosin coolants, those are an OEM choice but they're spendy.

Disclaimer: I'm sure none of this is recommended BMW solution, but I've come to the conclusion that they really only care about customers with deep enough pockets.
I have a trick for bleeding these stupidly-designed and under-engineered BMW systems...just dilute the coolant a little more that the usual 50:50 mix. I prefer 66:33 myself. t'll improve high-temp cooling performance, reduce pump cavitation and possibly give you a few more MPG. I'd also suggest a surfactant like RedLine Water Wetter. It's a little overpriced at $10 for a little 12oz. bottle but it honestly does help with heat transfer. Royal Purple has a similar product (Ice?), but I haven't tried it yet.

I tend to go for a 2:1 mixture, two gallons of distilled water & one gallon of Zerex or BMW pre-mix. That's despite the fact that we get some fairly cold weather up here...and I've seen engine blocks crack due to frozen coolant with my own eyes.

I did get myself the $90 Harbor Freight pressure tester. I wish it had a cap tester, and it's a little expensive, but it's already paid for itself a few times over. My '91 318i always had mysterious/random overheating problems. I managed to find three leaks without half trying. One of the radiator tank seams had a pressure leak and the heater core had a hole. I also replaced the pressure cap preventatively. Those late E30s with the DOHC M42 use a 2BAR system, it's infamous for overheating & cracked heads. When I swapped the motor into my 635CSi, the pressure tester immediately found three more leaks: a hole in the return hose, a loose clamp on the coolant neck, and a corroded radiator tube.

I'm pretty sure the M30 all used the standard 1BAR/15psi metal bayonet pressure caps. Newer BMWs use a screw-on plastic 2BAR/30psi pressure cap.

[iamjohn2407]

Yeah I used the Zerex G05 last because it was made to reproduce the OEM stuff from what I've read. I was already not doing a 50:50 because its damn hot here, I will look into the Water Wetter stuff though I've heard of it but didn't know exactly what it was for.

I could borrow one of those pressure testers again if need be, when you found the leaks did the tester lose pressure quickly? That's another tool that I haven't used much.

I was certainly wrong about the cap pressures, I'm not over used to dealing with Bar/psi on anything, and yes its one of those 16psi ones, I'll see if the store has a stock one when I go there to get the other stuff.

Again thanks for the help and suggestions.

[DesktopDave]

On both occasions I pumped the system up to 20psi, it held full pressure for about ten minutes. After an hour it had bled down a little, maybe to 15psi if I recall? I figured that was close enough. I believe the spec test is pump it up to 20psi, then no more than 1psi leakage per 2 minutes.

I'm not 100% sure those caps are all the same, but a few psi won't make much difference as long as they're good. I usually go with what part number is listed by BMW, they have a tendency to make small improvements during production. There are at least two cap part numbers listed, both are 1BAR, probably won't make much difference as long as it'll hold pressure.

First time I used my pressure tester it wouldn't hold any pressure at all. Then I discovered the block drain wasn't installed, I had forgotten to screw it back in after flushing the block.

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You don't shop at RockAuto, do you? They have great prices, great clearance deals & pretty quick shipping. Just be careful with shipping costs. Here's a link to '86 635CSi cooling system parts. I have a 5% discount code too, expires on the 23rd: 10766093887017449

[iamjohn2407]

So you did the pressure test with it empty then? I did it with fluid in that could have made a big difference.