Engine Bay getting warm and fuel overheating when towing

[TX Montero]

Gentlemen,

I was wondering if anyone else out there with an NM who tows a trailer long distances has noticed that the fuel heats up after towing for at least 2-3 hours?

My Pajero acts normally around town, but whenever I take a trip and tow my trailer, the fuel eventually heats up. The engine never gets too warm and the cooling system is operating normally. This has taken me several years to figure this out as I only take these types of trips 4-5 times per year, and it take a few hours of towing for this condition to occur.

I first started noticing this when filling up with fresh fuel. There are vapors coming from the fill tube which cause the filling station pump to auto-shutoff. I usually have to pump the fresh fuel really slowly until I can get enough in there to cool things down and then I can fill normally. When driving even longer distances, the condition can get much worse to the point where the fuel pump seems to choke trying to get a steady flow of fuel.

If I let things cool down a bit and put fresh fuel in there (I never let the tank get below 1/2 way) then I can drive for a bit again before the condition re-appears.

So, somehow too much heat is building up in the engine bay and causing the fuel, as it recirculates through the system, to eventually heat up. I thought that my exhaust manifolds were the culprit of the extra heat. This made perfect sense as mine were cracked, as everyones will on this model, and the fuel lines run close to the exhaust. Well, I replaced them and still had the problem.

All of this changes recently when I decided to simply release the hood (bonnet) to let it pop up a few cm. I tied it down so it would fly up while driving down the highway if the safety catch were to ever fail. So, this small gap between the body and the front of the bonnet allowed just enough air flow that I've never seen this problem again. I've done three trips like this now, usually driving between 7-12 hours each day (I live a long distance from the places I like to visit).

So, I have to think that someone else out there has been experiencing these same issues, but may have had just as hard a time trying to figure out the cause. I'm curious to hear others' experiences, if they are similar.

I'm now thinking of getting some vents or louvers installed in the hood just to get some air flow through the engine bay.

Anyone else experience similar issues with this model?

Anyone have any other ideas about the cause or cure?

Thank you so much for your assistance.

Regards,

Tony

[Wiseowl]

Some years ago had the same problem in international truck got hot and had trouble stopped on side of road let it cool down problem gone. We ended up lagging the fuel line I cannnot remember what we used but that fixed the problem we had. It was very hot weather at Warialda N.S.W we were carting grain in the farm truck it was a 6 cylinder.

[gaz1]

In Australia the system for putting fuel into the tank doesn't have those cutoff gizmos that detect the fuel vapours being vented to atmosphere. So even if the problem is happening here, it's unlikely to be obvious to the driver.

But I'd be curious to know if anyone else has tried the popped bonnet (hood) approach and got a cooler engine from it.....anything that can help on a hot day, when towing, could be a real boon. Louvres would be a more permanent approach.

Gaz

[TX Montero]

What's interesting about this scenario is that the engine coolant temp is normal. I believe it's simply the buildup of heat in the engine bay, as it's pretty well sealed at the top, that causes the fuel lines to get too warm over time and that's what heats up the fuel.

[green monster]

sounds like someone is trying to justify the need for a cool bonnet scoop to the missus,,,, what a great idea, would look cool and wouldnt do any harm,
I actually wondered if i might have the same problem it sounds familiar,,,, gotta go talk to the missus ,
Also once i fit the bonnet scoop, i will be open to suggestions as how i can convince the missus that we might as well put a Chevy LS1 V8 in the Paj, it would probably be more economical ,,, on fuel not tyres!!!!!
and yes im serious,,,,,,,

[steveandviv]

we might as well put a Chevy LS1 V8 in the Paj, it would probably be more economical ,,, on fuel not tyres!!!!!

What a great idea. How good would it go then

[TX Montero]

sounds like someone is trying to justify the need for a cool bonnet scoop to the missus,,,, what a great idea, would look cool and wouldnt do any harm,
I actually wondered if i might have the same problem it sounds familiar,,,, gotta go talk to the missus ,
Also once i fit the bonnet scoop, i will be open to suggestions as how i can convince the missus that we might as well put a Chevy LS1 V8 in the Paj, it would probably be more economical ,,, on fuel not tyres!!!!!
and yes im serious,,,,,,,

Actually, I'd be glad if I didn't have to do anything at all to the look of the truck. I'm pretty much done building it up and just want to take it on trips and enjoy it, but this fuel overheating not only causes issues driving it, but I think it's dangerous and annoying at the same time.

Now, the Chevy v8 might actually improve gas mileage, but gearing would have to change to keep the rpms lower where the power band of the v8 is.

[nervis]

you could try fitting a cooler to the return fuel line... something like a auto transmission cooler... would cool the fuel back down before it goes back into the tank..

[Stroker]

Hi Tony
Being from Texas you have probably seen a British car from the 70's with a Chrysler engine, the Jensen Interceptor. The later version of these with triple carbs had bonnet (hood) louvres to alleviate the exact same problem you have.

Cheers Glenn

PS I have seen 3 xr6 turbo falcons being driven with their bonnets up

[Patagonia]

Technically I have no clue of what can be happening but could it be that you have the evaporative emission system of the fuel tank obstructed?

regards

[sprintman]

I'm guessing the LHD version has fuel lines etc in different locations than ours and maybe near a 'heat source'. My 2c anyway..

[DougL3NC]

Never had an issue with mine in 155,000 miles...but I also never figured the fuel would have a chance to heat up since its leaving the tank and being consumed by the engine so damn fast!

On the contrary, I get a P0125 OBD II malfunction code all the time...P0125 is coolant too cool for closed loop injection. Funny, since these NM's are NOT known to be cool running vehicles!

Doug in North Carolina

[RoyHarvey]

Fuel problem

Technically I have no clue of what can be happening but could it be that you have the evaporative emission system of the fuel tank obstructed?

regards

I also have no clue, (yes I know, don't state the obvious) but I would be looking closely at the emission / fuel venting system.

[TX Montero]

Never had an issue with mine in 155,000 miles...but I also never figured the fuel would have a chance to heat up since its leaving the tank and being consumed by the engine so damn fast!

On the contrary, I get a P0125 OBD II malfunction code all the time...P0125 is coolant too cool for closed loop injection. Funny, since these NM's are NOT known to be cool running vehicles!

Doug in North Carolina

Doug,

This is Tony. I think we were having a similar conversaion on Expedition Portal today too. The Pajero world is a small one after all.

[TX Montero]

Gents, thank you all for chiming in so quickly. I really appreciate all the feedback. The fuel cooler was something I definitely thought of.

I was concerned about a couple things before going that route:

1) I just wasn't sure exactly which line was the return line and the best place to tap into the system.
2) I wasn't sure of the effects of adding that much more fuel line into the system. Would this add undue stress to the fuel pump? That is, wouldn't it have to work harder to keep up the same amount of pressure and flow over a longer distance? Maybe I could use larger fuel lines to help reduce the added pressure?
3) I was thinking that if heat is causing the problem, then this excess heat might deteriorate other components prematurely and that addressing the heat problem might have other benefits too, like preserving the life of any of the gaskets, rubber hoses, etc.