What do you think of this B&M trans cooler to fix my overheating?

I have a 1996 XJ 4.0 AW4. It has a one year old Modine 2 row radiator, new fan clutch, 8 month old thermostat, factory hoses, new temp sensors, etc. Coolant is new. There is a B&M transmission cooler mounted on the radiator in front of the mechancial fan.

My XJ will overheat on hot days (75*+). This occurs when idling, crawling, or on the highway. Basically any time you make the engine work. But when the temps drop and it gets cold the motor will run too cold. Often at 150* or 160*, but will warm up to temp when idling. I have replaced the thermostat with a factory 195 three times in the past year.

So here's what I plan to do.

I'm going to remove the current Modine radiator and transmission cooler. I'm going to replace the radiator with a CSF from Dirk, and run the power steering through the trans cooler built into this radiator. Will this work OK and would anything negative come from this mod? After this I would no longer have anything mounted directly in front of the radiator, which would allow for maximum air flow.

Now for cooling the transmission I am thinking about cutting a hole on the driver's side of the hood and mounting this B&M trans cooler:

http://bmracing.com/index.php?id=products&sid=4&cat=20&subcat=28&pid=75

It's 13.5" x 9.5" with a fan mounted on it which can pull 500 cfm of air.

This cooler has a thermostat which activates the fan once the trans reaches 175*. Would this cooler be OK to run independantly and be enough keep my transmission nice and cool on the trail? I would also run a temp gauge and manual switch to activate the fan.

The fan on the cooler can be set up to be a pusher or a puller. Which should it be? Should the fan be mounted on top of the hood or flipped over so the fan would be in the engine bay? Also what can I do to keep water, snow, and other debris out of this area?

I'm then going to replace the thermostat yet again, but this time I may go with a Robert Shaw 195 t stat.

And finally, would it be a good idea to mount a hood vent on the passenger rear side of the hood?

Oh, one last thing. Should I makeshift a splash guard under my engine bay to direct airflow or help create a vacuum?

Thanks for the input, let me know if you think of the trans cooler and if this will work.

48 views and no one has any comments?

have you tried a new high flow water pump?
i just installed a new one after mine seized up and it fixed my overheating tremendously.
and i put in "40 below" rad. fluid and it claims it reduces temperature of up to 40 degrees.
mine runs about 160* at idle then when running on the freeway and what not it will run an even 210*.
i have 4.88's so i run sort of high rpms a lot of the time

your engine should not be over heating with the factory cooling system. Trying to mask the real problem with fancy parts is not a good idea. Is the new water pump for a reverse rotation system? This is a common mistake when buying parts from parts stores, make sure you got the reverse rotation pump. I would take it to a good shop and have the system leak tested and checked out before shelling out money for fancy parts.

Was your rig overheating/running overly cool BEFORE you installed the new thermostat? This really sounds to me like the thermostat is stuck, or is sticking. I understand it's new, but it happens.

XJflexer said:

Was your rig overheating/running overly cool BEFORE you installed the new thermostat? This really sounds to me like the thermostat is stuck, or is sticking. I understand it's new, but it happens.

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when you get a new one, boil it first to insure that it does indeed open.

No change in swapping out the previous thermostats. It was running hot/cold before the thermostat changes.

I don't know what possible problem I could have with my factory cooling system, everything is brand new. Except maybe the water pump thing, but that is less than 1.5 years old and installed by a shop who specializes in Jeeps only.

I think one problem I have is related to air flow. I have a big trans cooler in front of my mechanical fan. Also an ARB bumper with lights and winch. Relocating the trans cooler would fix my possible air flow problem.

Would that B&M trans cooler w/ fan be adequate to cool my transmission? What way should I mount it?

If I read this right, you are gonna run the power steering through the built in tranny cooler. And you are also going to add in an external tranny cooler for the tranny. Other then the new CSF radiator, how is that going to help keep your Jeep's engine from overheating? Other then the radiator, none of the things you are adding have anything to do with cooling the engine.

91 Jeep Project said:

If I read this right, you are gonna run the power steering through the built in tranny cooler. And you are also going to add in an external tranny cooler for the tranny. Other then the new CSF radiator, how is that going to help keep your Jeep's engine from overheating? Other then the radiator, none of the things you are adding have anything to do with cooling the engine.

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I would be removing my current big B&M trans cooler from in front of the radiator, which should help a lot with air flow.

I could also relocate the heater core onto the passenger side of the hood and slap a fan on that too. But I don't want it to run too cold.

Your problem to me sound like your coolant is always circulating, and never having a chance to "rest" in the radiator. For example, the job of the thermostat is to restrict coolant flow from the radiator to the engine until the coolant reaches operating temperature. After operating temperature is achieved, and slightly surpassed, the thermostat will open allowing the coolant from the radiator to flow through the engine, thus lowering the temperature back to optimal temp.

If your cooling system does not restrict the coolant enough, and it continuously flows, the coolant will never have a chance to rest in the radiator and be cooled by airflow over the radiator (durring the summer), thus never effectvely removing the heat from the coolant and engine.

In the winter, if the cooling system isn't restricted, the coolant will never rest in the radiator to allow the coolant in the block to warm up to operating temperature and it is continuously flowing through the radiator, thus continually being cooled down and continually cooling the block.

NOW, if you had a waterpump problem, yes, the engine could overheat due to lack of coolant flow. BUT, then the fact that your engine runs TOO cool durring the winter wouldn't make sence. It would still run hotter than normal due to lack of coolant flow. Are you running a very low temp thermostat and didn't upgrade the fan switch to a lower temp as well?

90Pioneer said:

I would be removing my current big B&M trans cooler from in front of the radiator, which should help a lot with air flow.

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If everything is running right, this shouldn't be an issue. Mine has never overheated with this in front of the radiator.

My thermostat is a factory 195.

If something is wrong in my cooling system, what could it be? Nearly everything has been replaced.

XJflexer's coolant flow theroy seems logical, and actually very likely, but what would cause my coolant to circulate 100% of the time?

A bad thermostate sticking open. Same way they stick closed. Or a chunk of rust jammed in it, forcing it to remain open.

I would say remove the thermostat and boil it with a thermometer sticking out of the water. See what happens.

You might even want to just go ahead and put another one in there.

Did you actually flush cooling system? If not, flush the CRAP out of it to try and dislodge everything possible. Scale is NOT your friend....or your engines....