Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Trad Air Condtioning

Hi again Burgundy,

First, I should mention I am a big fan (pun!) of the 3.0 Roadsters. Great spec and only a few problems to sort.

Some years ago your verdict came up on a Roadster forum. I have many Roadster friends and I put up what they suggest on gomog. They were discussing whether there was anyway to improve the less than ideal Roadster cooling. I also dealt with two fellows off-group in depth. Like many, their AC was feeble, its was leaking and their controls had seized. One contacted an AC expert contacted in Dallas, (overseas Roadsters come standard with AC). That fellow asked me to get schematics. Morgan had been begun outsourcing all elements of design and production a few years before and the AC was another area they did so. Don't ask me how, but I got the schematics under the condition of discretion.

It was easy to spot the problem of the supplied system. It HAD TO to cause problems. I gather from you they did not address the issue by the time your car was made.

PROBLEM

1. ALL earlier non-AC trad Morgans have an rather awkward valve on a old choke cable. It shuts off the hot coolant flow to the cabin heater, which is virtually a small radiator that heats cabin air going into the cabin and most often has a bypass directing the flow back to the engine water pump. Any non-AC trad owner will tell you that, even with the cabin heater vents closed, unless the shut off valve is closed, the matrix continues to provide heat, radiant and from the unpumped engine airflow. The systems continue to heat the cabin!

2. In the AC cars it is worse. The designer chose to use the same passage for the cold AC air as is used for the hot air. This passage abuts and is above the matrix.

3. The designer did not install a shut off valve. No one at the MMC caught that. The cold AC air must go through a hyper-heated passage over the matrix constantly charged with hot coolant. A BIG NO-NO. This is a recipe for tepid damp air and lots of condensation. Many of the sufferers complained of a wet cabin floor and rusted controls
.
SOLUTION

For the cars made before a remedial fix, (if any) and before damage has occurred, the fix is theoretically easy. One must install a shut off valve and preferably a bypass for the hot coolant to return to the engine water pump before the climate unit.)

It is theoretically quite simple. And it works. And you can test it. The system has hot coolant flowing in and out of the cabin unit. Image below. To sorta test, merely clamp one of the hoses (in or out) which will stop the hot coolant flow. That alone might make a difference. However, I found that other manufacturers, like BMW use a dual purpose passage. However, they use a electric solenoid valve which stops the flow to the matrix and bypasses it back to engine water pump. I was so pleased with this that I switched (pun!) from a Morgan mechanical valve to a solenoid valve myself. I have now used it for many (12+) years. It does not break like the Morgan mechanical valve often does and I merely put in a toggle switch to replace the choke cable. You merely have to get a valve that is open when not active or power it from the ignition through the aircon switch.

I wrote an article on all this then forgot to add a link to the gomog Roadster page. https://www.gomog.com/allmorgan/CabinHeaters.html#BETTER

The solenoid valve (which should have three hose attachments, A. to the valve, B. from the valve to the matrix and C. from the valve to the return hose.) should cost about 35 quid which is the cost of the fix if you do it yourself. That is all you need. The result is your unit will stop leaking and the AC will be cold and dry.

Did I complicate your life?

gmg.

P.S. Here is a Roadster cooling schematic. I have others from the MMC. I cannot show the suppler diagram, but if you call Mark Evans or Mark Baldwin at the MMC they will probably send you when.

Lorne that makes complete sense. My system although on a +4 is identical to your diagram, thank you.

The T piece shown is plastic and is common to all trads of the era (My 4/4, +4 and Roadster).

Whilst in there, worth replacing with stainless steel. SiFab used to sell them ex-stock so I guess you will have to hunt around for one.

There is another plastic T piece on a Roadster cooling system that is unequal - the spur element is a lot smaller than the pipe it is connecting to. These have been known to break (Sorry, I cannot remember the TM user name of the gentleman who pointed this out to me). Well worth replacing this with stainless steel on any Roadsters so equipped. Again, you will have to hunt around for the part as SiFab was, AFAIK the only supplier.

The T piece on the screen wash can also break. Ebay has lots of options in copper. I agree I miss SIFABs help on these parts.

Using a three way electrically operated heater control valve plumbed to just bypass heater matrix would be a good solution. When heater matrix receiving flow the output would still be controlled by bowden cable operated heater box flap.

Only issue I can think of is stale static coolant being left in heater matrix during a long summer possibly gumming it up, although regular use of valve would likely solve.

Richard ... or just move up here and have the opportunity to use your heater on a regular basis year-round 😄

K

Yes K although no issues for me as natural air-con works so well. I recall a 35°C day the summer before last when driving Morton, with side screens off of course, was an absolute pleasure Just dreaded any traffic jams.

[BLUSH!!!] Well...for the last decade+, I am being told it works. Cheap fix. Not doing anything inevitably has the resultant condensation produced rust out the system. My apologies to you for missing linking to the article on gomog for so long. gomog is merely the result of idle intellectual exercise, like others doodle or do crossword puzzles.

By the way, I stumbled across a cable operated shutoff and bypass (rather than a solenoid) that should also work. (I didn't investigate it much) https://s-pautomotive.com/product/heater-core-bypass-control-valve/ Using a mechanical switch requires more driver awareness but eliminates the wiring I explained.

Now we need George or Davew to explain how the Roadster's cooling system functions. Schematic below. I am most interested in their thoughts and theories. I have yet to come to any conclusions on my own..though I would ask you all note the angling of the stock plastic radiator for a future discussion.


Hi Paul,

Return pieces have been used since the 1970s, merely higher quality ones then than now. I use one to this day. Image below. For some reason, they were left off when the MMC switched to Hotwire systems. Shutoffs were still used I believe, but no bypass. That leaves those cars with uncirculating coolant in the hoses to and from the cabin heater to become EXTREMELY hot as it runs (until GEMS) through the super hot valley under the intake/plenum. But without the bypass and circulation, you can imagine how hot that coolant got!! For 1984-2000 they changed the hoses to metal pipes in that section! IIRC, (without consulting gomog) with GEMS they ran hoses around the top of the engine outside the convenient passage through the valley. Kinda sloppy. But it confirms that LR or the MMC was aware of the problem they had created but they had forgotten the bypass solution. There is a consequent of buying out contracts of the older more experienced workers and replacing them with government subsidized "apprentices". That happened everywhere in the developed world.

gmg



ROADSTER COOLING SYSTEM SCHEMATIC

Any takers? I am really interested.

gmg

I can offer my slightly updated version for design and function of the 3.7 Roadster cooling system shown below if you wish Lorne?



It appears it would suffer just as 3.0 Roadsters and other trads if air-con option was fitted and therefore benefit from the same cure. Important (maybe more than other models) that a three way valve is used though to maintain flow through heater pipes when matrix taken out of circuit. This would need to be fitted on heater inlet plumbing and require a second T junction to supplement the existing (41). A four way valve may offer a simpler plumbing solution, ideally a two state type rather than proportional control via rheostat. Either would work though with return flow maintained under all settings.