Rough idling when hot

[OlgieD]

I've been playing in Landcruiser Mountain park last weekend and while that was heaps fun, it also highlighted a little issue. My Paj (a 89 V6) gets pretty hot when running in low gear for prolonged time, to a point where the water comes out of the system boiling hot (had a few leaks lately and haven't changed the water to coolant yet). When the engine gets that hot, it also starts idling rough, which gets dangerous as it tends to cut out. That's no fun going down a steep section and the brake booster looses vacuum and power steering is gone.
I'm planning to replace the water again with coolant, and while I'm at it probably take the radiator out and give it a good clean, and also have the injectors cleaned for better milage (hoping) and better idling. Will also be checking the extra fan on the front of the radiators.
Anybody else have any suggestions what I could also do to prevent it from overheating too much? Other than not use low gear? :-P
Or to have it idle smoother? The engine is a recon with some 60k on it, and generally runs very nice.
Cheers! Olger.

[PJDM1980]

All you can do is go through the basics

All you can do is go through the basics
-tune is right
-clutch/electric fans is working (clutch fan might not have any fluid/wax in it)
-thermostat is ok
-flush system
-change coolant use distilled water
-check hoses aren't crushing when getting hot
just a couple as i'm not to familiar with the V6.

[PJDM1980]

And the fan on the front or your radiator is for the A/C so i don't think that's a problem.

[bakerboy]

And the fan on the front or your radiator is for the A/C so i don't think that's a problem.

although it does reduce the cross section of ur radiator, as my aircon dont work im gonna get rid of the fan

[OlgieD]

OK, so far I've replaced my tapwater in the radiator with coolant, I know the thermostat is still good, as that's been replaced not long ago. It normally idles and runs good, though I stil need to get a proper tune up done.
Last weekend I ended up doing quite a bit of mountain driving around Mt Barney Nat Park, all on tarmac though, and noted that it was starting to heat up again. Nomally the temp needle sits well below half way, but due to relaxed driving up hill, hence low rpms, the engine was building more heat than the cooling system could disperse.
Considering the radiator fan is belt driven and rotates at engine speed, low engine speed while working hard means more heat buildup. So I'm thinking of replacing the stock fan with electric fans instead. The belt driven fan needs to be replaced soon anway due to cracks in the plastic. Added benefit is that I can turn the fan(s) off with a switch when doing a water crossing.
Does anybody have any experience doing this? Rather than have the fan(s) going at full speed all the time, I'd rather have them controlled and speed up as heat increases. In a dual fan setup, one fan could kick in delayed effectively saving the fan (or rather the bearings and elec.motor).
Cheers! Olger.

[bakerboy]

why would u want the fan turning off during water crossings?

[OlgieD]

Basically to prevent the blades on the fan to hit water while rotating, possibly causing them to bend and hit the radiator. My current fan (belt driven) has cracks in it, possibly from hitting water while rotating. It's just something I could do with electric fans, but not with a belt driven fan.
Cooling isn't a problem when going through deep water :-D

[bakerboy]

Basically to prevent the blades on the fan to hit water while rotating, possibly causing them to bend and hit the radiator. My current fan (belt driven) has cracks in it, possibly from hitting water while rotating. It's just something I could do with electric fans, but not with a belt driven fan.
Cooling isn't a problem when going through deep water :-D

i hear a lot of people saying this, but the fan is mounted behind the radiator, how would it hit it?

[PJDM1980]

i hear a lot of people saying this, but the fan is mounted behind the radiator, how would it hit it?

The water slows the fan rapidly and the fan blades try to spin and bend, moving forward into the radiator.

[PJDM1980]

looks like that but can be worse.

[hobbo]

Hey that interesting ! I didn't know thats why they drop the fan belt?, I thought they did it to stop water being thrown onto the dizzy leads and cap etc. only. Whats the vintage? Looks like 26 Chrysler?
Good One !

[bakerboy]

looks like that but can be worse.

true, but there is a fair gap between the fan and radiator, and imo would only lurch forward if u hit the water quite quick

[luifly]

I have 2 electric thermo fans (11" and 12") that i am going to be installing shortly and i would be interested to see the ways in which people have installed them or going to install them. I also like the idea of being able to control them when water crossing.

[OlgieD]

I've just purchased this from ebay http://cgi.ebay.com.au/ws/eBayISAPI....m=310162291074 which I hope to be fitting sooner rather than later. Don't like my engine cutting out due to heat just as I'm descending a very steep section...
As for the stock fans, the clutch mechanisme is supposed to engage when the engine gets hot, and let the fan spin faster. When you get into water, the engine would cool down and the clutch would disengage, effectively idling the fan, protecting the fan and radiator. This is fully automated, unlike what I'm gonna do which will require a label inside reminding me to turn off the fans when going through water... :-D
The pair I bought should fit fairly nicely on the radiator, they're only a few cm shorter. The only thing that'll prove a challenge is the sensor.
With an electric fan, you'll either have them blowing at full speed all the time, or use a sensor to engage and disengage automatically.
Cheers! Olger.

[nj swb]

Pajeros have good cooling systems. Mine copes with low range in loose sand in 40 degree heat. If yours is overheating (on bitumen!) something is wrong.

Start with your thermatic fan. It's not a clutch - it's a fluid coupling with a special silicone oil. When the oil is cold the fan will "slip", which reduces the load on the engine. As the oil heats the coupling stops slipping, and acts like a standard mechanical fan.

Over time, coupling fails to "grip" properly, so the fan never stops slipping - at low speed, the radiator has insufficient airflow and the engine overheats. I suspect this is your problem.

If you do go the electric fan solution, there are various solutions available to vary fan speed. There's been some discussion in the Auto Electrical section on OuterLimits.