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Magnum 5.2 on Xj

E

extractor

NAXJA Forum User
Location
Greece
Hi everyone.
I made an engine swap to my 2.5l xj.
I put the engine from a 95 Zj 5.2 and i have some temprature issues.
I bought a complete donor,so the engine didn't have any issues with anything.

The problem is that when the engine runs under load ,specially at speeds over 70mph and enviroment tempratures over 30 celcius gets very hot.I stop the car at 110 celsius.
I have 3row copper radiator.
3x 10'' electric fans
83c thermostat, all new
Any idea what could be wrong?
 
extractor said:
the problem is that i didn't have any issues when the engine was on the zj
Click to expand...

No, you shouldn't....the ZJ was MADE for that engine...the XJ was not.

Radiator size, air flow thru the grill to the radiator, fan size, all those things come into play......in the ZJ, all were engineered to work correctly for the amount of engine heat produced.

Now, you put a bigger engine that will produce more heat volume in an smaller engine compartment that was not designed for it.

You're just gonna have to figure it out...it's one of the things about putting a bigger engine where it was not designed to go.

go thru the basics

1) make sure the radiator & cooling system are 100% filled/vented
2) are both radiator hoses getting hot
3) sure the water pump spins the same way as the radiator is designed for
4) do you have a shroud on the fans
5) are you sure the fans are spinning the right way to pull air thru the radiator (sounds simple, but...)
6) did you use antifreeze & water, or just water
7) are you sure the exhaust is good and not plugged or restricted badly
8) are you sure the fuel pump is getting enough fuel under pressure to the engine since your xj had a 4 cyl, and you now have an 8 that requires more fuel
9) are you sure the transmission isn't slipping and generating heat under high load
10) does the heater work



Just a few things to look at........
 
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How does it run? Fuel pump ok? I had this problem on my car, the carb was running lean and caused it to overheat only on the highway. The fans aren't the problem if it's only at highway speeds, since there is more than enough airflow thru the radiator. Make sure nothing is restricting the radiator's air too.
 
trippled said:
How does it run? Fuel pump ok? I had this problem on my car, the carb was running lean and caused it to overheat only on the highway. The fans aren't the problem if it's only at highway speeds, since there is more than enough airflow thru the radiator. Make sure nothing is restricting the radiator's air too.
Click to expand...

as long as the fans aren't pushing air out, that is generally true, but not always
 
there is no place for shroud since i run 3 fans.
They work correctly.
i tried the same with pushing fans,but pulling i quiet better.
pure valeo antifreeze-no water.
i skip the exhaust issue....for now!!
The fuel pump as far as i know is the same,only the fuel presure regulator changes,but i run also lpg gas,so it runs the same.
No.the trasmition isn't slipping!

Lets'talk about the exhaust.
How this could increase the temp ??
it'new,after the exaust header,without catalyt converter, 70mm diameter muffler
 
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The temprature rises under load,mostly at high speeds,and at the trail when i go to uphill at low speeds for a "long distance" ( 1/2 mile)
 
extractor said:
there is no place for shroud since i run 3 fans.
They work correctly.
i tried the same with pushing fans,but pulling i quiet better.
pure valeo antifreeze-no water.
i skip the exhaust issue....for now!!
The fuel pump as far as i know is the same,only the fuel presure regulator changes,but i run also lpg gas,so it runs the same.
No.the trasmition isn't slipping!

Lets'talk about the exhaust.
How this could increase the temp ??
Click to expand...

1) running pure antifreeze is not good for an engine, as they are designed for a mix. pure antifreeze boils higher than the mix, but will not stop freezing. should be 50-50 mix of water & antifreeze

2) if you have no shroud, then airflow thru the radiator is reduced cuz there is nothing to make sure the air moves thru the radiator instead of just spinning around and around. All fans should have a shroud...why do you think auto makers spend the money on them. Think of a lawnmower...it has a chute to direct the cut grass out...without that, the grass will just keep building up till it stalls the motor out...same principle

3) I doubt the fuel pump is the same....the 5.2 likely has a higher volume, if not a higher pressure as well. Not enough fuel will make an engine run hot under load, and can burn valves and melt pistons

4) if the exhaust is not big enough or plugged, then all the exhaust gas/heat will not be able to get out, which will cause high back pressure, which can in turn cause a lean condition (see above) as well as melt other things near the manifolds/header AND greatly increase under hood temps. I once saw a engine running & the catalytic converter was plugged. The engine ran hot, and the exhaust all the way to the cat was cherry red. If ya can't get the heat out of the engine from the exhaust, the only place it will go is the coolant.

5) Ok, you use lpg....are you sure the pressures/flow are set right for the bigger engine ??? I mean you increased the engine size by 30%. Using LPG, the pump is a non-issue, but the pressure/flow must still be correct or you can still run lean under load


extractor said:
The temprature rises under load,mostly at high speeds,and at the trail when i go to uphill at low speeds for a "long distance" ( 1/2 mile)
Click to expand...

OK...so now we know it is NOT just at high speeds...which takes us back to the fans/shroud/airflow as the problem.......low speed and trail use all spell low airflow......


.
 
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do you think that a flat shroud could do any work?(flat because there is not enough space.
For a while i had one blade from the inside and 3 fans pushing.it was much better but i had a huge power loss.
The exhaust is much bigger than the stock,and new.
 
extractor said:
do you think that a flat shroud could do any work?(flat because there is not enough space.
For a while i had one blade from the inside and 3 fans pushing.it was much better but i had a huge power loss.
The exhaust is much bigger than the stock,and new.
Click to expand...

Ok, exhaust not likely then......a flat shroud would be better than nothing, but you should be able to make one that isn't flat.

You need to make sure airflow is directed thru ALL of the radiator cooling area, and not just what's in front of the fans......that's what the shroud is designed to do.

You also may not have enough flow with the fans.....just because you have 3 doesn't mean it is enough. I tried 2 big electrics (with shroud) on an old truck I had, and it wasn't enough, but 1 mechanical fan & shroud was......

if the engine needs 4000 cfm to stay cool at low speeds, and your 3 electric fans are only moving 1000 cfm or even 1200 cfm each....it ain't enough and you're overheating.

extractor said:
do you think that a flat shroud could do any work?(flat because there is not enough space.
For a while i had one blade from the inside and 3 fans pushing.it was much better but i had a huge power loss.
The exhaust is much bigger than the stock,and new.
Click to expand...

This right here is telling you you don't have enough airflow........if 4 fans cooled it better, then 3 fans ain't enough


.
 
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is it better to push or pull ?
3 row radiator is ok ?
there is 3" space between the radiator and the water pump and 1" between fan and pump.
 
Last edited:
3 row rad should be ok, but some have had little more cooling than a good 2 row

pulling air thru would be better if you can do it because the fan motor won't block the air until AFTER it has gone thru the radiator


losing 2200 cfm would definitely be a bad thing
 
whatever you can get....I have no idea over there.

I have pretty much stuck to stock, with an occasional added fan for extra cooling

I know there are several cars models over here that have high flow electrics, but not sure you could fit the motor/shroud in the space you have

The big thing, is get as much airflow as you can fit in the space you have...too much air, you can always use a temp sensor to turn it off.

Not enough, well, you have to turn the engine off.....
 
The only solution to clear some space is to move front the radiator.maybe with this and with the shroud from a 4 liter xj have some good result...
 
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