MyE28.com

The question you need to answer is, is the engine actually over heating or is the gauge falsely indicating over heating.

Todd and I have never done anything "special" to the cooling systems and we have never had an over heating issue.

As I said before, the twin turbo 6er has nothing but stock components for its make, model and year except for a Spal auxiliary fan to replace the 387 lb stock aux. fan... no colder t-stat, no lower temp fan switches, etc. It does have an VDO temp gauge with sender with its readings confirmed with an IR thermometer. The hottest it ever got was 210F while idling in traffic on a 95F+ day. It normally hovers in the 185F range.

What more can I say? While sitting idling you are making no more power than stock, therefore, you are not putting anymore heat load into the coolant than stock.

You are correct about the heat load being the same at idle. I think the heat retention in the engine compartment is greater however as there is more metal to absorb it. Additionally any cooling seen through the stock induction system has been eliminated as well.

When I weld a 1-1/4" thick flange to a 3" pipe it gets significantly hotter and stays that way much longer than when I weld a 3" elbow to a 3" pipe even though I am putting the same amount of heat into each weld. It has to do with the amount of available heat sinking material.

I would argue that a turbo has more material to heat sink than the stock system and I feel this is contributing to my particular issue.

Yes, perhaps more heat sink material and longer cool down time but, 10 lbs of iron at 200F is the same temperature as 10 tons of iron at 200F. With a set BTU input the 10lbs specimen will increase in temperature far faster than the 10ton specimen and will also decrease far faster. The temperature, however, does not go beyond the maximum that the heat source can provide without increasing the BTU of the source.

Hotter air coming into the intake will not increase the coolant temperature. It's hotter, less dense, so to maintain proper running parameters less fuel is injected to maintain a stoichiometric mixture.

I would confirm that you gauge is reading correctly. This is a simple voltage meter... change the resistance in the circuit (sender, wires...) and the voltage changes.

The point is, I know the 6er has zero cooling problems and it has even greater thermal capacity than the S1 or S2 kits as it has a bigger, heavier manifold, 2 turbos and more down pipe material in closer proximity to the engine.

Greg,
You need to verify the temp of the system with some other device. If you have a DVM, a temp probe for it is very cheap. Hell, the DVMs are very cheap also. You want to verify the pressure of the system also. The pressure tester caps are very cheap also. If all those check out OK, then you need to check coolant flow. That is more problematic to test.

Also, just because the fan on the fan clutch is spinning doesn't mean its spinning at the proper speed. I forget out to test the fan clutch. Maybe someone else can chime in on that.

RussC

Apart from increasing thermal load through increased power, installing a turbocharger puts heat into the intake charge which increases cooling system requirements; the reason our cars need a radiator and coolant is because we can’t control the intake air temperature.

A turbocharged engine at idle will generally make less power than it's NA counterpart but that doesn't necessarily translate into the same or lower coolant temperatures; power output and cylinder head temperature are only roughly correlated. In other words, power output and coolant temperature are, at times, inversely proportional. An example of this is when an engine detonates. As it begins to detonate, cylinder head temperatures go up even as power goes down. An interesting side note on detonation is that cooling (the removal of heat from combustion gases) improves significantly during detonation - which isn't to say coolant temperatures go down. Cooling improves during detonation because the barrier layer between the combustion gases and the chamber/cylinder/piston is broken down by the extreme pressures of detonation; heat transfer can improve so much that pistons melt.

At a minimum I’d make sure all cooling system parts are as new (including the oil pump). Flush the cooling system with a heavy duty cleaner to remove rust and scale, make sure the clutch fan is functioning properly, increase the size of the radiator and put in the lowest temperature thermostat. I seem to recall BMW making a mechanical fan with additional blades for use in later models which would also help.

Changing the coolant mixture has a significant effect on engine temperature:

russc wrote:I forget out to test the fan clutch. Maybe someone else can chime in on that.

I tested the fan clutch in my car by putting a rolled up newspaper against the fan blades while the engine was idling. The fan is suppose to stop if you do that; it did.

I then replaced the fan clutch... cooling is pretty important to overall engine health.

It's important to note that a fair number of cars in this thread (mine, Greg's, Skeen's) have no oil cooler of any kind mounted at present time.

Duke has one, but it appears he may be having other issues.

Jeremy

Jeremy wrote:It's important to note that a fair number of cars in this thread (mine, Greg's, Skeen's) have no oil cooler of any kind mounted at present time.

Duke has one, but it appears he may be having other issues.

Jeremy

Though, neither does the 6er

My experience too is that with a cleaning cooling system, temps are managed quite nicely.

I can barely get my NA 9.3:1 motor to get above 10:00 on the gooahj, even in traffic.

Now that I have my car up and running again, i'll post up some results.

I have a brand new Nissens radiator, old water pump and mechanical fan, 71 degree thermostat, and a 20psi radiator cap that I picked up at my local pep boys. I am running distilled water and a cleaning chemical through my cooling system right now because I had bad calcium buildup in the head and radiator. I will be switching to minimal anti-freeze, distilled water, and water wetter when the chemical treatment is done. I am located in Atlanta, GA.

I am running 10psi right now using a TCD manifold and turbo. I have an air/air intercooler and I am running Megasquirt 2 extra.

My coolant temperatures stay between 190 and 195 cruising around (ambient 90 degrees) according to my temperature sensor in Megasquirt which I would give a + or - 5 degrees. This is about 11:30 on the instrument cluster gauge for me. I plan on getting a more accurate temperature reading in the near future. Being off by 5 or 10 degrees with Megasquirt really does not matter because it's all relative to your settings and tune.

If I am driving around with the a/c on, I will see coolant temperatures of 200 to 205 which is about 12 - 1 on my instrument cluster gauge.

Here's my take on the cooling issue - my car(85 745i) never go over the 185 degrees when it was running 10psi with stock wastegate even when the ambient temp is 115 and the AC on full blast. After converting to MAF and wastegate mod to run 14psi the car now overheats to 210 degrees when stop for more than 3 minutes. I never let it go over 210 degrees so I do not know how high it would go if I let it. Nothing was done to the cooling system but I did change out the fan clutch after the first overheat and it did not change a thing.

I did not go high volume waterpump or smaller pulley because I did not want the accelerated wear of high spinning parts. I chose to cool the radiator better by blowing more air through it. I contracted a cooling company to test and designed a electric fans set up by giving them a spare radiator I have. Here's the final product -


The fans are controlled by Spal's programmable fan controller and now I do not have any problems while idling in 120 degree weather here. The fans come on at 50% speed at 175 degrees and full 100% at 195 degrees. I am also working on an upgrade for the aux fan since I am a Spal dealer and can play with the stuff. I am hoping to swap it out for a high performance fan that can double as the cooling fan for the whole system to give me a double safety should one or the other efan(s) fails. The shroud will be modified again to add one way slots for when the new aux fan comes on.

Also please note that I am running 140A alternator from an E32 as the stock alternator is not putting out enough.

ecartoys wrote:... the car now overheats to 210 degrees when stop for more than 3 minutes. I never let it go over 210 degrees so I do not know how high it would go if I let it.

Why do you consider 210 degrees to be overheating? That might be hotter than you care to get, but that's hardly a dangerous temperature. You're not even close to boiling over at that temperature if you're running the proper mixture of coolant under pressure.

How deep are those fans?

Also, does anyone know the clearance differences between the engine and radiator between a 745 and 535?

Shawn D. wrote: Why do you consider 210 degrees to be overheating? That might be hotter than you care to get, but that's hardly a dangerous temperature. You're not even close to boiling over at that temperature if you're running the proper mixture of coolant under pressure.

Sorry forgot to mention, when my addon temp gauge says 210 the factory gauge is touching red. This is coming from a car that never exceeds 185 add on gauge or noon on stock gauge so I am not taking any chances to find out how accurate the gauges are or how high a temp is not too high. Either way it is higher temp than optimum. I am running 60/40 mix with G8 coolant, distilled water and water wetter. Summer here is 110 to 120 degrees so AC is always full blast.

The fans are 2" thick. Clearance on 745i is 3" with spin on waterpump. Bolt on water pump gets 3.5". If E28 is the same as E23 733/735 clearance is 4" to 4.5".

ecartoys wrote:

Shawn D. wrote: Why do you consider 210 degrees to be overheating? That might be hotter than you care to get, but that's hardly a dangerous temperature. You're not even close to boiling over at that temperature if you're running the proper mixture of coolant under pressure.

Sorry forgot to mention, when my addon temp gauge says 210 the factory gauge is touching red. This is coming from a car that never exceeds 185 add on gauge or noon on stock gauge so I am not taking any chances to find out how accurate the gauges are or how high a temp is not too high. Either way it is higher temp than optimum. I am running 60/40 mix with G8 coolant, distilled water and water wetter. Summer here is 110 to 120 degrees so AC is always full blast.

I wasn't suggesting you let it run hotter and hotter until you find out how high is too high! My Auto Meter water temp gauge (with the sender next to the senders in the thermostat housing) shows straight up as 195 and 210 to be where the needle is at the right side of the "water" part of the ideogram (not next to the red).

cgraff wrote:

M635CSi wrote:

cgraff wrote:On another note....about the new 335i ....twin turbo factory fresh from BMW....right?

Well here's a dirty little secret.
-Chris

Wow, that's good information. I wonder what the "official" reasoning is for the US to receive watered down versions?

I wouldn't be too quick to blame BMW engineering though, I'll bet it was those infernal bean counters that did it.

well....they're getting mighty desperate if ONLY the US market automatics were missing the oil kuehler but all other market automatics had it.

Recently, BMW issued a bulletin stating that if a customer complains about high engine temps on a 335i to install an oil cooler retrofit. Note, this is only for the 4-door as the coupes come standard with an oil cooler, odd huh.

Just to update this thread...

I have still not had a problem with overheating and I have been driving my car now for a couple of weeks. I have been driving it every day in Atlanta, GA with the A/C on in the hottest part of the day in downtown traffic. My temp gauge on the instrument cluster never goes past 12:00 and according to megasquirt, this is about 200 degrees. The apsolute only time that it goes past 12:00 is if I make a full second gear pull to redline and then stop immediately afterwards. My temp gauge might creap up to 12:30 or so, but will come right back down as soon as I am moving again.

I am running 1 bottle of water wetter and distilled water (no antifreeze). I guess radiator upgrades aren't as necessary as I had originally thought.

I do not have an oil cooler installed either.