AI generated specific to P6 but most likely also applies to P4
The core engine cooling architecture of the Morgan Plus Six and its donor BMW B58 engine is largely identical to BMW's cooling architecture—utilizing BMW’s advanced map-controlled electric water pump, split-cooling circuits, and ECU-managed electronic heat management module.
The differences lie entirely in the packaging, radiator fabrication, and auxiliary expansion/plumbing integration necessitated by Morgan's aluminum chassis.
Core SimilaritiesInternal Engine Flow:
Both share the B58’s split-cooling layout, which can thermally isolate the crankcase from the cylinder head during cold starts to reduce emissions and speed up warm-up.
Electronics & Thermostat:
Both rely on the stock Bosch/Siemens engine management framework to command the electronic rotary valves and variable electric water pump speeds.
Coolant Type:
Both systems are specified to run BMW HT-12 coolant mixtures.
Key Differences
Radiator Design and Durability:
BMW utilizes mass-produced, highly integrated multi-component plastic-tank radiators mapped precisely to high-volume front-end crash structures. The Morgan Plus Six utilizes bespoke, low-volume hand-fabricated radiator units packaged into the classic narrow nose cone. These custom setups have historically suffered higher rates of stress or vibration-induced cracking compared to mainstream BMW installations.
Expansion Tank and Plumbing Layout:
While a standard B58 installation in a BMW passenger car uses a tightly integrated factory expansion tank and dedicated routing paths, Morgan adapts the peripheral layout using custom header tanks, unique hose lengths, and distinct fill lines tailored to the CX-generation bonded aluminum platform.
Bleeding and Servicing:
Filling or bleeding a drained cooling system on a Morgan CX often requires strict adherence to specialized vacuum-fill procedures to avoid dangerous air pockets or hot spots in the hand-routed lines.
Last edited by JohnHarris; 05/08/26 04:19 PM.
