Smaller Water Pump Pulley?

[Moss]

Has anyone looked at getting a smaller pulley for the water pump so it spins faster to get higher flow? Could a cheap and effective mod.

[anthonygubbin]

IMHO I doubt whether the benefits woudl be worth the trouble. You would need a shorter belt, the pully mount on the pump would need to change so that the new pully would fit. Given that you might as well go a higher flow pump.

Regards A

[Moss]

Just thinking if would be possible to do a straight change out of just the pulleys (3 small bolts). Change in diameter would only have to be small so a new belt wouldn't really be needed as it could probably be taken up by the belt tensioner.

[kjparker]

one thing you also need to consider, faster flow doesnt necessarily mean better cooling!

Some people actually slow the coolant down in order to get more stable temps and better performance!

Have a look at this link... http://jeep-xj.info/HowtoRadiatorRestrictor.htm

[Dustbowl]

Great idea Moss, but the longer the coolant is there the more heat it soaks up (within reason) your flow rate is right, the XJ overheating is solved by more airflow ;)

[jtb007]

faster spinning pumps arent always good, you can get cavitation and things like that......

[Moss]

Great idea Moss, but the longer the coolant is there the more heat it soaks up (within reason) your flow rate is right, the XJ overheating is solved by more airflow ;)

There seems to be common misconception here that slow flowing coolant is better for cooling. Heat transfer is dependant on the difference in temperature of the coolant and engine. In other words the cooler the coolant, the higher the heat transfer rate and more heat is transferred to the coolant. When slow flowing coolant flows through the engine it increases temperature which means a smaller change in temperatures between the engine and coolant which means the coolant becomes less effective. Not to mention inconsistent engine cooling due to the fact that coolant cools the engine more where it enters and less where it exits. In other words, when coolant heats up it becomes less effective.

I'm a bit sceptical that air flow is the primary issue because when I'm on the highway (where there is plenty of airflow) it still gets hot and I have to turn the air con off. I understand that the engine is under extra load but it should be able to manage quite easily at normal highway speeds.

[Moss]

faster spinning pumps arent always good, you can get cavitation and things like that......

I'm only talking about increasing the flow by about 20-40% nothing too major. I don't think it would cause cavitation especially since its a closed loop.

[Steve F]

....I'm a bit sceptical that air flow is the primary issue because when I'm on the highway (where there is plenty of airflow) it still gets hot and I have to turn the air con off. I understand that the engine is under extra load but it should be able to manage quite easily at normal highway speeds.

Then you have some other problem, at HWY speeds the fan is redundant and the coolant is already flowing at a decent rate etc. I'd be replacing that water pump as it could be corroded enough to not be efficiently circulating the coolant. A well maintained stock system will keep the XJ cool enough. I run 35's and did the Cape last year with no overheating issue despite being loaded up for a month away. Other than an aftermarket radiator and a heavy duty fan clutch my cooling system is stock.

Cheers
Steve

[Moss]

Then you have some other problem, at HWY speeds the fan is redundant and the coolant is already flowing at a decent rate etc. I'd be replacing that water pump as it could be corroded enough to not be efficiently circulating the coolant. A well maintained stock system will keep the XJ cool enough. I run 35's and did the Cape last year with no overheating issue despite being loaded up for a month away. Other than an aftermarket radiator and a heavy duty fan clutch my cooling system is stock.

Cheers
Steve

I just had a look at the water pump and it looks brand new. I have flushed the system twice this year (with coolant flush and a garden hose) and use CAT ELC. With the air con on and doing 110km/h on a hot day it will fairly quickly creep up to 105 but thats when I turn the air con off.

[Steve F]

I just had a look at the water pump and it looks brand new. I have flushed the system twice this year (with coolant flush and a garden hose) and use CAT ELC. With the air con on and doing 110km/h on a hot day it will fairly quickly creep up to 105 but thats when I turn the air con off.

It looks new on the outside or inside? ;)

Cheers
Steve

[anthonygubbin]

I searched on here yonks ago and have read many post re overheating. 9 out of 10 times it comes down to the clutch fan. Mine has started to get hotter than normal this year and the first thing I will be doing if it becomes probelmatic will be to change the clutch fan.

Regards A

[Moss]

It looks new on the outside or inside? ;)

Cheers
Steve

The impeller looks new.

I searched on here yonks ago and have read many post re overheating. 9 out of 10 times it comes down to the clutch fan. Mine has started to get hotter than normal this year and the first thing I will be doing if it becomes probelmatic will be to change the clutch fan.

Regards A

If were a fan issue than it would ok on the highway.

[Moss]

one thing you also need to consider, faster flow doesnt necessarily mean better cooling!

Some people actually slow the coolant down in order to get more stable temps and better performance!

Have a look at this link... http://jeep-xj.info/HowtoRadiatorRestrictor.htm

That's my point exactly, the cooling is working too effectively and they have to reduce the flow.

IT's not like a high flow electric water pump where the flow is consistent. You'd still have the flow proportional to engine RPM.

[anthonygubbin]

If were a fan issue than it would ok on the highway.

My prob is on the 80kph highway. I have never experienced the issue before and the pump is only 12 months old and is a good brand. Nothing has changed on mine in the last 12months except that I flushed it three months ago. I don't think that putting a smaller pully will help if the issue has only arrisen in the last two weeks. To keep the XJs cool you need air flow and the air flow is designed to come through the grill and under the floor hence why bonnet vents are not real benificial when at normal speeds, but that is a side issue. IMHO I still think the clutch fan helps draw in the air at normal speed ranges once the engine bay temp gets hot. I could be wrong but that is the only likely scenario for my higher operating temps this summer. I admit yours might be a different issue but like said, nearly all the overheating threads have people changing their fan to resolve the issue what ever the driving range may be.

Regards A

[jtb007]

I'm only talking about increasing the flow by about 20-40% nothing too major. I don't think it would cause cavitation especially since its a closed loop.

closed loops systems can still cavitate

[jtb007]

I'm only talking about increasing the flow by about 20-40% nothing too major. I don't think it would cause cavitation especially since its a closed loop.

closed loops systems can still cavitate...... you need to look at the pump curves and all that stuff before you go changing rpm on the pump..... ventually youl get to a point where it wont pump anymore..........

[Moss]

closed loops systems can still cavitate...... you need to look at the pump curves and all that stuff before you go changing rpm on the pump..... ventually youl get to a point where it wont pump anymore..........

I agree 100% about cavitation in closed loops but closed loops have a higher system pressure which reduces cavitation.

You can just apply affinity laws to find the increase in pump performance.

Pumps do become less efficient when they run outside their optimum speed and flow but no water pump runs at optimum specs since it is dependant on the engine speed.

What I want to do, for example, when the engine is at 2000RPM the water pump would be spinning as if it the engine would be at 2500RPM. Worst case, giving it some would be the same as redlining normally, well within the pumps limits.

[Steve F]

I ran without a clutch fan for a bit and as long as I was moving overheating wasn't an issue. Only had to get to around 40 to cool it down. I had the electric fan going but it couldn't do the job by itself when under higher loads.

Cheers
Steve

Sent from my GT-I9300 using Tapatalk 2

[junglejuice]

Has anyone looked at getting a smaller pulley for the water pump so it spins faster to get higher flow? Could a cheap and effective mod.

I see that you have the diesel, most of us have the petrol model, for mine (petrol) the only time it has overheated or had any temp problems were the result of the radiator, check the cond of the radiator as far as water path AND the air path make sure there are no blockages.
The 4.0 litre 6 is a big lump of an engine that fills the engine bay, the TD on the other hand is a lot smaller, not sure how that effects things as far as airflow goes.
I am also unsure what temp a TD normally runs at but mine runs at just under 100 in traffic, on the highway ac on or off doesn't matter, if anything the ac helps as the fans run faster in mine with the ac on....

BUT whether it is petrol or diesel, mods AREN'T required to keep these running at the right temps, maintenance is the key, mods should only be for improvements or change of operation....

[Wooders]

I'm a bit sceptical that air flow is the primary issue because when I'm on the highway (where there is plenty of airflow) it still gets hot and I have to turn the air con off. I understand that the engine is under extra load but it should be able to manage quite easily at normal highway speeds.

Really if the vehicle is overheating in general hwy conditions you have a problem. Changing the WP speed isn't fixing the problem.... sort of like stubbing your toe and putting a band aid on your knee. ;)

[anthonygubbin]

Just a quick hijack, as I need to wait before sending another PM. Dave what is a clutch worth for my fan and do you have one in stock ;). Also well spotted JJ I assumed he had the 4.0. I would have thought the diesel would have less overheating issues.

Regards A

[Moss]

Let’s face it, cherokees don’t exactly have the best reputation for their cooling systems. If you read the manual about overheating causes; steep hills, traffic, high ambient, air con. To me (as an engineer) that’s a bulls**t excuse for bad engineering and/or budget.
Mine is fine on the highway under ‘general’ condition. It’s not until you add you add a few factors together that I see some issues. I want to be able to drive on soft sand with the air con on a hot day which is what most well maintained cars are capable of doing, hence the reason for trying to improve the cooling. I’m trying to think outside the box. Little improvements here and there add up quickly. I’m not going for cheap bandaid fixes and I don’t think this will fix the problem but I do think it will help.

[junglejuice]

I have been up the cape with mine running 30" tyres on stock gearing towing a camper trailer through the sand etc on quite warm to hot days with the ac on and it still sat on the normal temp running the original (12yr old) radiator!!!

Mine never has an issue in traffic or hills, the only time it did have an issue was with one particular aftermarket radiator....

[kj69]

mine has only over heated when the radiator fins were full of mud , been wheeling on stinking hot days up massive steep hills only air flow from fan never over heated , soft sand working its ass off never over heated ,xj cherokee motors run hot they are designed that way.half the stuff you read about xj`s over heating is crap .

[anthonygubbin]

mine has only over heated when the radiator fins were full of mud , been wheeling on stinking hot days up massive steep hills only air flow from fan never over heated , soft sand working its ass off never over heated ,xj cherokee motors run hot they are designed that way.half the stuff you read about xj`s over heating is crap .

I know mine overheated the other day as the coolant boiled ;). But having said that it has never been an issue before; even when crawling in Tassie and drving the Perin Dunes.

Regards A

[kj69]

I know mine overheated the other day as the coolant boiled ;). But having said that it has never been an issue before; even when crawling in Tassie and drving the Perin Dunes.

Regards A

Trying to say there is a cause for them to overheat and the cause is not design it is something wrong (fault ) weather that be the radiator fins being blocked or internal blocked core or clutch fan .
the design works as long as ALL parts in the system are functioning , the xj has a smallish radiator for engine size and if one part of the system is not doing its job the other parts wont cope then you get the dreaded over heating xj.

[anthonygubbin]

Trying to say there is a cause for them to overheat and the cause is not design it is something wrong (fault ) weather that be the radiator fins being blocked or internal blocked core or clutch fan .
the design works as long as ALL parts in the system are functioning , the xj has a smallish radiator for engine size and if one part of the system is not doing its job the other parts wont cope then you get the dreaded over heating xj.

Yepp mine has something wrong with it for sure, like I said earlier if it happens again I am changing the fan clutch. I suspect it is the original one the vehicle came with so is probably time for a new one. The radiator bloke who fitted my bar five months ago said the fan should have been locking up a little more than it appeared to be. My rad is pretty new and get regular flushes so I am leaning away from rad diagnosis.

Regards A

[Moss]

This is turning into 'what I have done without overheating'. I'm talking about the TD not the 4.0L.

The fact that everything has to be 100% in order for it cool and that any little defect causes cooling issues means that the cooling system is inadequate. When engineers design things they calculate what they need and then add a 'Factor of Safety'. It's fairly obvious that the factor of safety for this design was not great enough.

[kyphonii]

If your jeep is boiling without a temp in the red then your radiator is not holding correct pressure, try a new cap.
The Jeep is designed to run 95 to 110 and can go higher for short periods, why is every one trying to run their Jeep under what they are designed for. Its so old school to have a car running at 85.

[junglejuice]

This is turning into 'what I have done without overheating'. I'm talking about the TD not the 4.0L.

The fact that everything has to be 100% in order for it cool and that any little defect causes cooling issues means that the cooling system is inadequate. When engineers design things they calculate what they need and then add a 'Factor of Safety'. It's fairly obvious that the factor of safety for this design was not great enough.

Obviously the point you missed is that in my case even with a 12 yr old radiator towing in harsh conditions mine was still operating effectively (so obviously there is some safety factor otherwise it would have overheated!!), if yours is struggling in normal driving then you have a problem, something isn't working as it should so you need to get everything to be working as it should before you even contemplate modifiying it.

I'll put it in different terms, it is like a box trailer that is rated to carry 1000kgs but when you put 500kgs in it the axle bends, your modification thinking is to put extra bracing on the axle to handle the weight that it is rated at but ignoring the fact that the axle is severly rusted.....

[Bogged]

Have you checked your thermostat is opening fully and at the correct temp?
The td has more room around the engine so it should be cooler with the airflow in the engine bay, but diesels do run hotter due to the turbo.

Exhaust wrap, turbo covers and larger inter coolers can help dissipate the heat. There are a lot of diesel owners here and in Europe that don't have issues with overheating, so I'd be looking at the cooling system. Clogged heater core, radiator, cracked hoses, dud radiator, thermostat, clutch fan, aircon fan (check that the aircon condenser isn't clogged or have damaged fins as this will impede airflow to the radiator.

Every little bit contributes.