Cooling Advice

[Guest mcramsay]

Well one problem sorted and onto the next. Took the marlin out for its longest run yet 15 miles of A roads! Only to find it still really struggles to keep cool. Above 50 the temp sits at around 92. ( which may be high as the thermostat opens at 80) anything under 50 the temps creep up, I was driving along at 40 with the rad fan running and sitting around 96 degrees, and I would have overheated without the fan for sure

 

This prompted some major relocations of things over the weekend. My aim was to move the radiator as close as possible to the front grille, and relocate the 15" kenlowe fan to the rear of the radiator, this meant I had to move the oil cooler (still to find it a new home or get rid of completely) and raise the nose cone by 5mm to allow the rad to move forward.

 

So it started out looking like this :

 

And has ended up like this:

 

 

My next plan is to completely duct the radiator to the grill all round so the air has no where to go but through the rad,

 

I run up the car and found the silicone hoses were quite hard when up to running temp... I wasn't sure if this was normal so I jerry rigged a tyre pump into the header tank to pressurise and test the cap. With 12 psi in there the hoses were as hard as they were when running, and the cap lifted at 13 psi.... as it should. Im still not sure I'm happy with it...

 

Is it normal for hoses to get hard ( still squeezesble with some effort) when at temp? ( the standard m3 coolant system is fitted with a 2.0 bar cap which would make the hoses harder)

 

Finally should I relocate the oil cooler or get rid and just use the existing pipework to bypass the cooler entirely? The cooler runs on a thermostat and I've never felt it get hot, I believe it was fitted to the m3 for track use but I'm not sure if in the marlin it really is required....

 

Any help or feedback would be much appreciated.

[Guest Tim Norman]

Can the hot air get out from under the bonnet?

Can the incoming air get passed the radiator?

Modern engines do run a lot hotter than the older pinto. Better fuel economy apparently.

[Guest mcramsay]

I have side panel lourvres, and I plan on getting the bonnet louvres done ASAP. I was going to test with the Bonnet on and then off to see if that makes a difference.

[Guest mcramsay]

Just had a thought pop in my head and wanted to confirm

This is the expansion tank I am using,

 

Should I be filling this to above the radiator return line at the top so the fluid then passes out the top overflow pipe into a recovery catch bottle

 

Or filling it up halfway so that the air pressure on the top part of the tank pressurises the cooling system?

[cb750]

I fill mine to the top. The expansion coolant flows out to a collection tank and pulls back in to the expansion tank when the engine is off.

[Longboarder]

Baffled as to its function if you fill it and add a spit and suck overflow. It is surely meant to be part full when cold, fuller when hot, but still with a bit of space. The expansion of coolant from cold to hot should not overflow. The air filled space when cold is supposed to take the increased volume of coolant when hot. If overfilled it is meant to eject the excess coolant permanently. Isn't intended to suck it back in.

It does have a second role as an air trap so circulating air can get in and trapped in the tank through the middle connector but not re-enter the system through the bottom connector. Pressure is supposed to be higher in the pipe connected to the middle connector than the pipe connected to the bottom connector so there is some flow in through the middle connector.

Cap should be pressurised to lift at whatever, 13psi on yours to let out excess air/coolant but should allow vacuum re-entry of air to dissipate the vacuum and stop hoses collapsing.

 

Nigel

Edited March 12, 2017 by Longboarder

[Guest mcramsay]

That is exactly how I am running my set up, just wanted to make sure that was correct, which it seems is.

[fry61]

Your engine in the BMW could run at 134 *C before boiling ( 2 bar cap ) --- with your lower 1bar cap boiling is at 120 --- are you worrying un-necessarily ? Maybe just change the cap.

[Guest mcramsay]

ive not actually boiled over yet, but the car is well on the way to doing so, which shouldn't be happening when driving along. Also the stat opens at 80 and (on the m3 production car) electric fan kicks in around 92. So in my current set up in operating beyond the design of the engine, not looking for perfection I just don't like seeing the temp steadily rise to 100 when doing 40mph! Doesn't fill me with much confidence!

[Guest Gargoil]

You can't have too much radiator, is there any chance of fitting something bigger or thicker, even if you have to get a much thinner fan?

Ducting will improve cooling performance but if temps shoot up when driving slowly it's possible the cooling system is being overwhelmed by the demand.

I had something similar on both the Exmo and the GTM, and a new bigger better rad did the trick.

[Guest mcramsay]

I can fit something slightly bigger but I would have to go custom, I can't find anything that is the right shape to fit, I know of one other m3 marlin owner but cannot get in touch to see what he has done. The current rad is 50mm thick and I don't want to go any thicker, I have some playing around to do, test drive again at the weekend to see if the work makes any difference. I'm thinking of reducing the fan size to uncover more of the rad core, the fan should only be required during traffic, so having a massive fan might cool the car quick at idle but I'm not looking for speed of cooling at idle.

[Guest grimbo]

looking at the picture there looks like the air can get round the rad very easy can you make some panels to go round the rad so all the air coming in the front gets forced though the rad not round it

[Snapperpaul]

Try a lower opening temperature thermostat

The 80 degree stat you run will start to open at 80 and take a few more degrees to open fully.

You can wedge the rear of the bonnet and if that makes a noticeable difference on a test run there is a problem to be solved

[fry61]

Original M3 gauge ( as in donor ) what did that read at working temp.? If a cool/med/hot clock face then you have no answer -- could you run the OEM gauge & see where that runs.

[Guest mcramsay]

New ducting panels are getting made at work tomorrow and will be installed tomorrow night, this will make sure the air can only go through the rad.

 

The OEM gauge reads cold, normal and warning. But googling suggests normal operating temps to be between 82-90. Managed to track down another m3 marlin owner who can run 92ish on cruise which I would be over the moon with. He initially suffered cooling issues to start with and followed the same path as me which looks promising, only difference is his rad is marginally bigger but is custom made for marlin years ago so I can't go and buy one.

 

I'm fairly confident that moving the fan to the rear exposing the front of the rad with a completely ducted nose cone should work.