Heater Matrix/core bypass-A/C issue observation results
 

So, I am battling with a black Disco in FLA summer conditions and thought I would experiment with a few things and report back:

To begin with: New Radiator (4/13) & 180 degree Tstat....Original viscous fan clutch, 4 y/old water pump and original condenser fan.

For all those of you who commented that a heater core/matrix bypass was no big deal...WRONG! Ultragauge confirmed that the bypass added about a 12-20 degree difference, depending on the driving conditions. I almost had a heart attack when it reached 220, although it was about 97 degrees and 80 percent humidity in stop and go with a loaded truck and full blast AC

NOW, that being said, the cabin temps have been MUCH cooler...In particular the HOT air that was bleeding out of the center console lower vents (that would hit you about knee height on either front side AND the rear lower opening) are now ICY! This sounds to me like a blend door issue that has haunted Land Rovers forever according to some research.

So, I am toying with the idea of a supplemental Electric condenser fan to help the temps and get cooler AC performance.

Thoughts, comments?

Wow...that's quite a jump in temp. Thanks for posting that!

No bypass; no loop, but shut-off for summer, open for winter with a 3/4" brass ball valve:

---->P1000960.jpg Photo by Innernet | Photobucket

The A/C evaporator does not fight with the nearby heater core any more.

Well, how did you bypass? Loop, or dead end each line? I would vote for loop, as that coolant flow is part of what makes coolant go thru the metering holes on the D2 thermostat and decide when it will open. Slow the flow, you slow the response of the thermostat.

As for the 220 temp, was that when driving under 35 mph? You may want to check the viscous fan clutch. When warmed up, spin, release, it should stop in under 1 revolution.

The blend doors may have let your AC provide extra cooling, so in effect you have been running warm....

Those of us without factory air in old Chevys used a valve on firewall to kill hot water flow to the heater core. But IMHO the Land Rover needs the flow, so a "T" bypass valve may be a better way to go.

I did a loop with a preformed curved piece from Advance Auto. (I'll try to add a pic later) NO KINKS whatsoever. It seems the heater matrix in the cabin helps dissapate heat at the expense of driver comfort. I will check the fan clutch and possibly either replace the condensor fan OR put in a supplemental 8 or 9 inch in front of the AC condensor.

YES, it was under 35 mph when the temps reached 220, and it seemed like once it got that high, there was never enough open road to get it cooled back down before another red light...Clutch???

I'm no cooling expert, but to me there's no doubt that the heater core plays a huge role in cooling. I wouldn't bypass in the warmer time of the year without doing the inline thermostat mod. I know some will say the stock style 180 thermo is just as good as an inline, but I'm not sure I agree. I have had 3 motorads fail on me and I was luckily able to not roast my motor by turning my heater on full blast.

Suspect the clutch. The D1 radiator (3 rows) is a lot bigger than the heater core, so to a D2 (single core) the heater core is a larger percentage of the cooling surface available. My point would be that if you are seeing that kind of spread, there may well be something going on with the main radiator air flow. The D1 runs the electric fans all the time when AC is on, and has two; the D1 runs it when da brain thinks it is needed. Da brain can't see the traffic backed up a mile ahead.

As to " I have had 3 motorads fail " this has been heard from others, and I would advise the LR 180 stat, or the in-line stat. Rovers North and others get like $25 more than the Moto Rad. That isn't even half a tank of gas....

Any of you thinking about by-passing the heater core should read the 2 pages on the Rave regarding it's function and then hopefully you will not do it.
As for getting the a/c colder, check your freon level, these older Discos develop very slow leaks over time and most are probably running in the 30 pound pressure range on the low pressure hose when you should be up to around 50 pounds when the outside air is in the 85 to 100 degree range.

So Im guessing you never did it then or reversed it?

If you do bypass it, do it this way so coolant flow at various places remains the same. Early D1's have a heater valve that controls flow thru the core (lets it corrode more in summer) and later have the "always flowing" mode as in the D2. Some people reverse heater core connections to force flow against the grain of built up scale, and make it flush out over time.