Considering a bigger better radiator.

[zellamay]

My 98 Z3M still gets hot at highway speeds. We've had a few hot days here in Phoenix, (105 today, but it happened at 97 also), and it's happening again: temp gage gradually rises at speeds above 75 mph. If I slow down or turn on the heater, I can get it back to 12:00 position. I've read the threads, checked everything, burped it, etc. I have fan delete with an aftermarket puller fan on the back of the radiator. I've started 2 other threads on this topic, and thought I had it solved each time. It's not a matter of fans and shrouds, it happens only at highway speeds. I've made sure it's not the air flowing around the radiator. Tstat/water pump/radiator are good. It doesn't leak any rad fluid. Now I wonder whether a bigger better radiator would fix it. If so, which one? Seems like opinions vary on the 3 row S54 radiator. The $330 Mishimoto seems like the right one, but I'd appreciate recent opinions.

[GG///M3]

Get the oem s54 z3 s54 rad. Skip the mishi


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[Randy Forbes]

By shrouds, do you mean that it does have the one between the bumper & radiator?

[rf900rkw]

The S54 radiator is not three row. Unless you go with the full setup including oil cooler, it has less cooling capacity then your stock one.

As I have alluded to in my old threads, the S52 is the biggest engine, yet has the smallest air intake, even smaller than the 4cyl. Everything has to be perfect, and even then they can run hot at highway speed, especially in heavy/close traffic. The mechanical fan actually does help in those conditions. Odd but true. Not needed at low speeds, but apparently overcomes the crap airflow of the M bumper.

My answer was to pack the front with the largest cooling surface area I could. This is a Zionsville big boy plus an oil cooler. With custom shrouding. Running temp is now 79C. So far the highest it's gone is 81C, but it was only 90F that afternoon

[zellamay]

I'm gonna try it: mechanical fan back on. Not that hard to do as an experiment.

[Mr Bingley]

I added oil cooling, a Stewart pump, a Zionsville rad, Zionsville shroud, and Spal puller. Runs cool and oil temps never over 200 deg, and I'm supercharged.

[rf900rkw]

Yeah, should add that. I'm supercharged also, but that shouldn't matter at cruise speeds. I think the oil cooler makes the biggest difference, especially on the Zionsville where you're not giving up radiator capacity.

[CB750]

It doesn't leak any rad fluid. Now I wonder whether a bigger better radiator would fix it. If so, which one? Seems like opinions vary on the 3 row S54 radiator. The $330 Mishimoto seems like the right one, but I'd appreciate recent opinions.

If you're not going to install the OEM S54 oil cooler, don't waste your time with the S54 radiator option: S54 Radiator and Oil Cooler Installation

"I'm a bit puzzled why some people have installed S54 radiators without installing an oil cooler as a "cooling upgrade"; the S54 radiator is the same 32mm thickness as the S52 part, but the core is shorter to accommodate the oil cooler. However, the aluminum Behr S54 radiator does have two extra cooling tube rows (42) compared to the 40 row BMW / Valeo S52 radiator I installed during my previous cooling system refresh. I'm skeptical that two additional tube rows provides much of a cooling improvement."

I'm not convinced that installing the S54 radiator and oil cooler made a great deal of a difference for me. 75°F air temps last night, 75 MPH, and while the heavily buffered OEM gauge stayed firmly planted at 12:00, the Torque app was indicating 95°C, which is farther above the 88°C t-stat opening point than I would expect. I'm suspicious that the thermostat might not be opening fully; if a new t-stat doesn't change things, I may be looking at either a Mishimoto or modifying/changing the M front bumper cover.

[gmushial]

The S54 radiator is not three row. Unless you go with the full setup including oil cooler, it has less cooling capacity then your stock one.

As I have alluded to in my old threads, the S52 is the biggest engine, yet has the smallest air intake, even smaller than the 4cyl. Everything has to be perfect, and even then they can run hot at highway speed, especially in heavy/close traffic. The mechanical fan actually does help in those conditions. Odd but true. Not needed at low speeds, but apparently overcomes the crap airflow of the M bumper.

My answer was to pack the front with the largest cooling surface area I could. This is a Zionsville big boy plus an oil cooler. With custom shrouding. Running temp is now 79C. So far the highest it's gone is 81C, but it was only 90F that afternoon

Isn't this a two sided problem: 1) bad/limited airflow in M bumper, but 2) also limited exit ability for air once it's in the engine compartment? ie, if there was better exit potential, it might be easier to flow more in and thru through the radiator?

[rf900rkw]

Greg, yes. As best as I can tell, the natural airflow doesn't want to go through the radiator,. it wants to go over and under the car. Getting sufficient flow and then getting it to merge back in will be the development this season./

[ProductUser]

My 98 Z3M still gets hot at highway speeds. We've had a few hot days here in Phoenix, (105 today, but it happened at 97 also), and it's happening again: temp gage gradually rises at speeds above 75 mph. If I slow down or turn on the heater, I can get it back to 12:00 position. I've read the threads, checked everything, burped it, etc. I have fan delete with an aftermarket puller fan on the back of the radiator. I've started 2 other threads on this topic, and thought I had it solved each time. It's not a matter of fans and shrouds, it happens only at highway speeds. I've made sure it's not the air flowing around the radiator. Tstat/water pump/radiator are good. It doesn't leak any rad fluid. Now I wonder whether a bigger better radiator would fix it. If so, which one? Seems like opinions vary on the 3 row S54 radiator. The $330 Mishimoto seems like the right one, but I'd appreciate recent opinions.

My temp gauge stays just to the right of center at all speeds. Since I needed better data to understand the actual temp, I hooked up my torque app and turned on verbose logging to get a better picture of the temp swings during various driving conditions. In the end, the temp was fine and I stopped looking at the water temp gauge. BTW -- I have a stock cooling system, including the mechanical fan.

Tony

[gmushial]

Greg, yes. As best as I can tell, the natural airflow doesn't want to go through the radiator,. it wants to go over and under the car. Getting sufficient flow and then getting it to merge back in will be the development this season./

Thinking about exit via cowl - where you should have a high velocity/low pressure stream to bleed back into? Or via wheel wells? Or... ??

[rf900rkw]

Thought about. Rejected because convertible.

[BimmerBreaker]

What about the bumper underpanels, are those all in place?

Hitting 105 yesterday here in Phx and my Z got a little hot too. Within spec, but my debuffered cooling gauge was moving up on the highway.

Im honestly considering setting up the windshield reservoir with a more powerful pump to spray water on the radiator during critically high temp situations. If i pulled off on the highway with the gauge there it would have gotten real hot once I idled at a red light.... Though maybe more work than its worth, Ive had this car through two previous summers on a worse condition cooling system and it was fine... Actually Im better off now running a lower temp fan switch. In fact, ignore this whole thing, I dont need to spray water on anything. Except tailgaters maybe

[CMM3]

I have been running a Mishi radiator in my Z3M s54 track car for 3 years and it works great. I run with no mechanical fan or shrouds factory or otherwise and once moving the temp never goes above 170 F. on the hottest days. And this is with a high output stoker motor. I have an electric pusher fan that replaced the stock aux fan only because I removed just about everything that is stock and it only comes on when the car is sitting still and it cools it plenty.

With a mishi radiator you could put the stock mechanical fan back in to help at low speed, keep your puller electrical fan if it will fit, although it may not fit with the wider core, in this case put the stock aux pusher fan back in and it should solve your Problem.

I'd also be running purified water with water wetter if I were you. But be sure to use water that has been purified by reverse osmosis and NOT DE-IORNIZED OR DISTILLED. Wall mart sells it as Great Value brand (green label) for a buck a gallon. You also don't want water that has any minerals added. De-iornized or Distilled water is actually a bad thing to use at it is depleted of all of it's minerals, and will recapture it's minerals by depleting them from your engine. If your in AZ you'll never need antifreeze anyway. Running this will also help improve on the cooling efficiency of the system some.

[ProductUser]

I have been running a Mishi radiator in my Z3M s54 track car for 3 years and it works great. I run with no mechanical fan or shrouds factory or otherwise and once moving the temp never goes above 170 F. on the hottest days. And this is with a high output stoker motor. I have an electric pusher fan that replaced the stock aux fan only because I removed just about everything that is stock and it only comes on when the car is sitting still and it cools it plenty.

With a mishi radiator you could put the stock mechanical fan back in to help at low speed, keep your puller electrical fan if it will fit, although it may not fit with the wider core, in this case put the stock aux pusher fan back in and it should solve your Problem.

I'd also be running purified water with water wetter if I were you. But be sure to use water that has been purified by reverse osmosis and NOT DE-IORNIZED OR DISTILLED. Wall mart sells it as Great Value brand (green label) for a buck a gallon. You also don't want water that has any minerals added. De-iornized or Distilled water is actually a bad thing to use at it is depleted of all of it's minerals, and will recapture it's minerals by depleting them from your engine. If your in AZ you'll never need antifreeze anyway. Running this will also help improve on the cooling efficiency of the system some.

That's not a true statement; we see sustained temps well below freezing in parts of AZ.

[zellamay]

What about the bumper underpanels, are those all in place?

Hitting 105 yesterday here in Phx and my Z got a little hot too. Within spec, but my debuffered cooling gauge was moving up on the highway.

Im honestly considering setting up the windshield reservoir with a more powerful pump to spray water on the radiator during critically high temp situations. If i pulled off on the highway with the gauge there it would have gotten real hot once I idled at a red light.... Though maybe more work than its worth, Ive had this car through two previous summers on a worse condition cooling system and it was fine... Actually Im better off now running a lower temp fan switch. In fact, ignore this whole thing, I dont need to spray water on anything. Except tailgaters maybe

I understand. In AZ we get crazy trying to beat the heat. But you are right, a water sprayer wouldn't help much, imo. Obviously, you can't just spray for an hour while you drive the car. I think turning on the heater does more, but then the cab becomes a torture chamber.
Yes, I have the panels in place.
Do you have the non-M bumper cover? I'm considering hacking on my M cover to create better airflow to the radiator. I still have not finished repairing it from my crash. I repaired it to the right shape, but have not finished sanding and painting, so now is a good time to hack on it. I'm considering removing/replacing the center portion with what would look like a splitter. My rough math says I could add 30-50% to the air coming at the radiator.

[gmushial]

Thought about. Rejected because convertible.

With the fan delete, and thus the extra several inches of clear space btwn the radiator and water pump et al, might it be possible to duct the air back down and under the car... or is that a positive pressure area? [though one would think that the pressure gradient would go downhill from the front of the rad to under the car.. ?? ] Or do you have some magic up your sleeve??

[rf900rkw]

Dan, your car is not really comparable to the street cars. For one, you have modified airflow, an airdam pushing more air into the radiator and less under the car. If anything, it shows that improving airflow is more important than the radiator size. And you do have shrouding, according to the other thread. You just don't have a fan shroud.

Greg, in my case I filled the old fan space with radiator. I am really interested in making the side vents functional. But I have plans an materials for undercar shrouding that needs to be finished first.

[CMM3]

Dan, your car is not really comparable to the street cars. For one, you have modified airflow, an airdam pushing more air into the radiator and less under the car. If anything, it shows that improving airflow is more important than the radiator size. And you do have shrouding, according to the other thread. You just don't have a fan shroud.

Greg, in my case I filled the old fan space with radiator. I am really interested in making the side vents functional. But I have plans an materials for undercar shrouding that needs to be finished first.

You're correct with the air dam there is some additional air being directed up into the radiator and I do have hood vents which helps airflow as well so definitely different. But you may ave seen an older thread cause I don't have any shrouding at all.

I would mention that in my previous configuration I had a stock M bumper with no splitter, the stock Aux electric fan, stock mechanical fan and most of the factory duct work with a Zionsville HD radiator with the stock fan shroud. With this set up I never had any heat issues running on the track on 100F plus days. And I think I could make a case for having reduced air flowing when running on the track to the car in general as I was often close behind other cars at high speed. I do believe there is added cooling capacity that may help the OP in going to HD radiator. It certainly won't hurt and they are for the most part indestructible compared to the plastic counterparts. So if you're going to keep a Z it can be a good investment.

[rf900rkw]

I was referring to your (re)build thread.

"Not sure what you're running for a radiator or how you're controlling air flow. I have a Misimoto heavy duty radiator and I've used the stock lower oil cooler duct to deflect incoming"

That tells me you're running the shrouding leading to the radiator. Otherwise, all the air from the lower opening would just exit stage-down; go under the radiator. Many, many people do the "S54 upgrade" and find those pieces no longer fit, so they toss them. That's how you end up with way less cooling with the S54 rad.

I suspect the hood vents are a BIG part of it. Except.... the 6cyl Z3 shows none of the high-speed/traffic sensitivity of the M, The only two things it has is a bigger bumper opening and a less complex, better fitting underbelly shroud. It stops at the radiator, doesn't go back nearly to the rack as the M does.

[Tallyho322]

I pulled my mechanical fan off, verified that my electric fan comes on (wired correctly I guess), and have been monitoring actual coolant temperature with an ODB app.

Seems the car car will run up to 212-215 degrees F before the Aux fan kicks in (just tooling around town).

Once the fan fan kicks in, seems to hold coolant temp in the 200+ Range. Going to drive it on the interstate tomorrow @75-80 mph and see how she does. Expect to also be I. Stop and go traffic some on the ride home.

Is that hat temperature range normal? The dampened temp gauge stays in the center of the dial.

Greg

[GG///M3]

I pulled my mechanical fan off, verified that my electric fan comes on (wired correctly I guess), and have been monitoring actual coolant temperature with an ODB app.

Seems the car car will run up to 212-215 degrees F before the Aux fan kicks in (just tooling around town).

Once the fan fan kicks in, seems to hold coolant temp in the 200+ Range. Going to drive it on the interstate tomorrow @75-80 mph and see how she does. Expect to also be I. Stop and go traffic some on the ride home.

Is that hat temperature range normal? The dampened temp gauge stays in the center of the dial.

Greg

Just order a lower temp fan switch for my z3 coupe. My car isn’t running a fan clutch setup. It will most likely have an s52 with some boost swapped in the near future


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[KJ79]

I pulled my mechanical fan off, verified that my electric fan comes on (wired correctly I guess), and have been monitoring actual coolant temperature with an ODB app.

Seems the car car will run up to 212-215 degrees F before the Aux fan kicks in (just tooling around town).

Once the fan fan kicks in, seems to hold coolant temp in the 200+ Range. Going to drive it on the interstate tomorrow @75-80 mph and see how she does. Expect to also be I. Stop and go traffic some on the ride home.

Is that hat temperature range normal? The dampened temp gauge stays in the center of the dial.

Greg

Greg, I would like to hear from other S52 owners as well who have done the fan delete and are using real time temps from OBD2, not the dummy gauge in the dash, because I too have seen your exact scenario as described above to my dismay. Its not all the time, but under enough stress in the warmer weather, I have seen your exact numbers. My electrical fan kicks in at 212-214F as well.

Car is absolutely fine when moving without mechanical fan, it is in warmer weather stop and go, coming off the freeway, or under a prolonged load at lower speeds, like taking my long twisting one lane road home for 1/2 mile. Very little airflow, 35% incline. Tons of load. Disaster.

To me, and some may say these numbers are fine and arbitrary, it is too close to a problem for my comfort and one electrical mishap away form a run away train. Now I could wire a spal, figure all that out with diagrams and such and shroud fittings, and still not have it pull as much air as the stock setup from what I can read. I'm not going to lie, I am very worried about the fan seizing, exploding, taking out a few hoses and quite possibly put a dent in my hood. But, my hood actually has a very slight dent in the nose already (bought it that way), and hoses, radiator, expansion tank, etc.....those are things I can fix. That's a Saturday. What I can't fix, is a melted head. And a blown head gasket. And I have know clue how to mill down a block, and take it all apart and put humpty dumpty back together again. And I could learn, sure, but, at heart I am an enthusiast, not a die hard mechanic, and that is a project I truly wish to never have to tackle.

So I reached into my trunk, put my mechanical fan back on, and was immediately back to my usual topping out at 206-207F. Electric fan never even comes on with mechanical in there. It doesn't need to. It is the back up, not the primary. And per my other thread commenting on weather stripping being taken out, I can have that number down to 199F in the same conditions. She breathes. And for me, those 15 degrees or so is nothing to shake a stick at, is unnecessary heat on the entire engine compartment, and adding pressure buildup on an already aging and frail plastic system.

I check my mechanical fan every couple of weeks to make sure it is in good working order, and I monitor my temps almost daily this time of year. We are cool as a cucumber, and that is truly what I am after.

Some will say just add a lower temperature switch in the radiator. And this is a good option for keeping temps cooler and that fan kicking on sooner, but, there's pros and cons to every compromise and that is putting extra stress and work on the electrical fan. I think what it comes down to most, is do what you feel most comfortable with. That is how you will be happiest. And that is what your M is all about.......

[rf900rkw]

I have said it a billion times before. The fan is NOT controlled by engine temp. It is controlled by radiator temp. The fact that your engine outlet temp approaches 100C before 88C coolant reaches the sensor points to a flow problem. Going to an 80C switch will not stress the fan any more, you will end up with nearly the same duty cycle, just at a lower radiator temp. Keep in mind the fan runs any time the A/C button is on.