Disco 2 Cooling problems under load

[Trevor]

I'm down in Moab and the D2 is experiencing some issues with overheating. Here's a bit of an overview of what has transpired:

I arrived a few days ahead of the rest of the crew so I decided to do a solo run of Fin's and Things on Wednesday. No problem, no heating issues. There are a few small fins and ledges to climb on that trail; but nothing major. Its a short trail so in the afternoon I decided to run a trail that goes over the La Sal mountains. That's when I first noticed the problem. Once I started into the long climb up over the mountain she started to get hot.

I didn't let it boil over, it was still well below the red line. However at that point I noticed the seam on the expansion tank was leaking fluid out pretty aggressively. I turned around and brought her back to town....no heating problems at all once I quit climbing. I was lucky and Bill Davis at GBR in Salt Lake had a expansion tank in his parts Disco, so he pulled it and shipped it to me. It arrived today, I installed it, works great, no leaks.

But I took the vehicle for a drive up the Slickrock loop road which has some good, long, climbs, and same thing, she starts to overheat under load. I can drive it around town all day in 28 degree weather with the AC on and it won't overheat. Start climbing for any period of time though and it starts to overheat.

So I'm thinking I might be seeing signs of combustion gases in the cooling system. I'm going to see if I can get the rad sniffed tomorrow or perhaps pickup a combustion gas test kit from one of the parts stores here. That will at least tell me if I need to be looking for a new engine, that will be a different thread.

What I'm wondering is, is there anything else I should be checking? I do have a new expansion tank cap coming from Salt Lake City Land Rover tomorrow that I'm going to swap out. I doubt its that, but if its not holding pressure that might be the cause. Worth noting I replaced the original rad with a Brit Part rad a few years ago and it has never provided comparable cooling. I guess it could be the cause if it had some tubes clog or collapse. If the exhaust gas test comes up negative that would be my next guess. I don't think its a thermostat problem simply because the vehicle has no heating/cooling issues at all when its not climbing long hills. Also, I checked the oil, no sign of antifreeze there.

Anyway, just looking for additional ideas on things to check. Assuming it doesn't get worse I can limp it along and just avoid the trails that involve climbing mountains.

[Red90]

Check the viscous unit on the fan.

[Cruzer]

I had the same issue in my 2000 and after replacing the thermostat it cleared and seemed to cool allot better

[Trevor]

One thing I forgot to mention was I replaced the fan with an electric unit, which as best as I can tell is working well.

I think I'll get a new thermostat ordered from Land Rover Salt Lake. It's a cheap and easy swap. Perhaps its not opening complete and causing problems.

[Trevor]

I should have also noted that I'm not seeing any sign of oil on the coolant either. It's quite clean.

I am going to try the thermostat swap, I'm hoping I can get a Saturday UPS delivery.

[binch]

at risk of stating the obvious.....did you have a look at the fins to see if they are obstructed (dead bugs, seeds, grass. maybe a small child? ;D

What about your water pump....Have you ever had it changed?   Maybe it's not pushing water as efficiently as it once was.....?

[Trevor]

No small babies in the rad, or blown apart fins Bill ;D.

The fan is a new Flex-a-Lite Black Magic electric unit, and was installed over the winter. I originally thought it might be the root of the problem simply because it's the new bit in the system. But I can't see any issues at all with it. The fan comes on at the proper temp and moves a lot of air.

The water pump is only a couple years old. I replaced it at the same time I did the rad. It's possible that its the problem, but I would expect to be seeing cooling problems a lot more broadly with a failed pump, rather than just under load. I'm also not hearing anything odd from the pump that would suggest its ceased or blown the impeller apart.

[Trevor]

Combustion gases in the rad fluid came up negative, so that is a very positive sign.

But no good thing can go unpunished....as I was refilling the fluid I managed to break the (PLASTIC....AAARGH) bleed screw on the top rad hose assembly.

Edit: for future reference, a 3/8" fine thread (it's a 1.00 pitch requirement) socket head cap screw will do in a pinch as a replacement for the bleed plug.

[Matt H]

Check your transmission fluid. Climbing steep grades puts a ton of heat into the transmission cooling system. It's a function of the torque converter that max torque multiplication comes at high engine rpm and low transmission rpm. The shearing of the transmission fluid inside the torque converter under these conditions causes massive heat build up.

Seeing as the engine and transmission coolers are located in the same place, additional heat is transferred to the engine coolant from the trans fluid. At low speed/high ambient temperatures there is only so much air the fan is able to draw through the various coolers. That's part of the reason why I cut holes in my hood.

So check the fluid. If it has discoloured or smells bad you could be cooking the transmission slightly. IIRC a D2 transmission has warning lights for temperature? But if it is within spec they won't illuminate however considerable heat can be allowable before the light comes on and can cause problems in other, seemingly unrelated, systems.

My 2c.

[Trevor]

Hadn't thought along the lines of the transmission side of things, good info Matt. I did check the fluid, it looks in good shape, no discoloration or burnt smell. It was down half a quart which surprised me a bit as I just changed the oil last fall. Topped it up and also had a good look at the intercooler and it did have a bit of mud crapped on it, so I washed that off.

I didn't have any heating issues today, but then we weren't on a trail that I'd expect to see that problem arise. I doesn't look like my thermostat will be in until Monday now so I'll run it again tomorrow and see how she holds up.

[Matt H]

Yes. It could simply be a case of the less efficient BRITpart engine rad not being able to handle extra heat imparted from the transmission under those high torque, low speed conditions. Being down on fluid won't help either as you have less available for heat transfer. If the transmission fluid were to become too hot I would expect the transmission warning light to come on. Driving slower in a lower gear will help in the short term. Try to match engine and transmission rpm as closely as you can to minimize fluid shear (heat build up) in the torque converter.

It's worth noting however that during production of the D2 there was a "Saudi Spec Grill" offered in V8 powered vehicles destined for parts of the world (ie Saudi Arabia) where high ambient temperatures and low speed (traffic/deep sand) conditions warranted more airflow across the coolers. It was a less restrictive design that basically replaced the familiar bar type grill with an open mesh type.

If it does turn out to be the transmission putting too much heat into the engine cooling system changing to this style of grill or adding an additional transmission cooler (or both) would be good options. Especially the grill as you could easily swap it back to stock in winter.

[Trevor]

Well since topping off the transmission and pressure spraying the intercooler and lower rad, cleaning out the mass airfloor sensor and giving the air filter a good  cleaning, high temps have not presented themselves again. We ran 7 Mile Rim today which starts off with a very long that is more significant than what was causing heating issues before. So that's a positive sign.

Oh, regarding the Saudi grill, didn't know such an option existed. Wouldn't add much for me though as most of my grill is cut away to allow me to mount my winch bumper and winch.

[binch]

But no good thing can go unpunished....as I was refilling the fluid I managed to break the (PLASTIC....AAARGH) bleed screw on the top rad hose assembly.

Edit: for future reference, a 3/8" fine thread (it's a 1.00 pitch requirement) socket head cap screw will do in a pinch as a replacement for the bleed plug.

You'll be happy to know there is an aluminium replacement for the plastic piece  ;)

Good to hear you're back up and running with minimal adjustment;-)     By any chance have to turned down the temp for the fan to come on at?   So it starts cooling a few degrees cooler....... ???

[Trevor]

That's good to know Bill, I'll be ordering a few of those. Regarding the fan, yes, I've had its engagement point dialed right down during my troubleshooting. It's current setting is lower than its initial setting, but not at the lowest possible setting.

[Red90]

From what I can tell, if you just want the screw, it the same as BMWs, so common.  http://www.fgtmotorsport.com/products/brass-upgrade-coolant-reservoir-expansion-tank-bleeder-screw-for-bmw-mini-cooper-replaces-plastic-oem

Dorman 902-404 for the plastic that should be at any auto parts store: http://www.dormanproducts.com/itemdetail.aspx?ProductID=51988&SEName=902-404

I "assume" it is M10x1.0 and not 3/8" UNF.  That is a pretty common size used on euro vehicles for sensor connections.