Cooling System

Reference Pages:
OVERVIEW from the DeLorean Motor Company Technical Information Manual:  
The DeLorean has two (2) electric fans for radiator cooling mounted at the front of the vehicle. These fans are activated when the engine coolant temperature exceeds 97° C (206° F) and deactivated at 91° C (195° F). On the temperature gauge in the instrument cluster, this is typically one needle width or thereabouts above and below the first mark at the 8 o'clock position. Operation of these fans is controlled by a temperature switch (commonly called the "otterstat") located on the coolant return pipe in drivers side of the engine compartment. 
NOTE: The bung on the metal pipe containing the temperature switch should be installed so that the wiring terminals on the switch face downwards. This is to avoid trapped air in the system causing the switch to read the wrong coolant temperature and cause erratic fan operation. On early cars, the metal pipe is routed around the back of the Air Conditioning Compressor and is not able to be rotated. We suggest that such vehicles be converted to the later hose routing by adding the later part water pipe PN 110131 and hose PN 108675, as well as the hose retaining clip PN 108682. Another option is to cut the metal line aft of the bung, install another short section of 1-1/4" hose and two clamps, and then rotate the now-separate shorter section as described. 
For more details, refer to the Radiator Cooling Fans article in the Electrical Section. 

The water pump, located at the rear of the engine, is belt driven by the crankshaft pulley. The thermostat is housed in the top of the water pump under the thermostat housing cover. The thermostat housing cover is equipped with an air bleed screw used to purge the air from the coolant system when refilling.

Coolant leaving the engine is directed through a series of pipes and hose couplings along the left side of the vehicle center tunnel to the radiator. Coolant leaving the radiator is directed through a series of pipes and hose couplings along the right side of the vehicle center tunnel to the engine. The coolant expansion tank (header bottle) (fill point) located on the right side of the engine compartment, is connected to the coolant return pipe by a hose. The plastic originals are prone to failure from age and heat, and now it is common to see a stainless steel replacement coolant expansion tank used.
Due to the complexity of the DeLorean cooling system, periodic maintenance is essential. We recommend that the system coolant be replaced every 2 years with a 50-50 mix (premix) of a name-brand aluminum-friendly coolant. See procedure below. 
Check the coolant level periodically. Remove the coolant cap with the engine cold and verify that the header bottle (coolant reservoir tank) is 1/2 full. If you have to add coolant periodically, then there is a leak somewhere that must be addressed. The system will not "use up" coolant. 
Check the belts every 3000 miles. Failure of the water pump/alternator belt will result in an almost instant overheat of the engine and possible damage including failed head gaskets. 
Also see: 
The most common cooling system maintenance (after replacing the coolant overflow tank) is to replace all the hoses and clamps in the system. This can either be done piecemeal (i.e. replace hoses as they fail) or all at once. Considering that every hose failure will required you to dump and re-bleed the system, after a couple of part replacements it will become obvious that the best course is to update everything all at once. 
We sell the hose kit in two forms, a Complete Hose Kit PN K118674 and a Complete Hose Kit with Radiator PN K118675. If you still have the original radiator, its long past its useful design life and should be replaced at the same time. These kits contain all the hoses, clamps, coolant cap, heater control valve, and temperature switch needed to replace all hoses and clamps in the system. 
Replacement of the hoses is straightforward (but time consuming). Refer to the Water Pump and Radiator articles for details on accessing the hoses inside the engine, and the radiator. 
Step 1 - drain the system. If you separate the two hoses at the center/rear of the car (about where the frame widens out around the engine) you will empty everything but the engine block. Otherwise you'll continue to dump coolant every time you take off another hose. Not much fun! We also recommend pulling the two engine block drains (using the same 8mm square tool as the oil drain plug). One is above the oil filter, the other is above the catalytic converter. 
Step 2 - working your way across the system remove each old hose, sand the ends of the aluminum cooling pipes, and install the new hose and clamps provided. 
Step 3 - You will find two 3/4" hoses inboard of the right front tire, these connect to the heater core. You can access the core end by removing the panel under the spare tire. CAUTION: The heater core is relatively soft brass. This is one place that you don't want to overtighten the clamps as you can collapse the tube causing a leak. 
Step 4 - Remove the right hand trailing arm shield. If the studs spin or break off, they can be replaced from above with an improved stainless retainer PN 111230. Access the longer 3/4" heater core hoses that connect the small aluminum tubes to the back of the engine. NOTE that one of the hoses is larger at one end than the other, the larger end goes to the heater pipe and the top center of the engine. If you are doing the complete kit, refer to the Water Pump article for information on removing the intake manifold. That provides much better access to the other end of these hoses, and the heater control valve, but it can be done from under the car. 
Step 5 - Once you have replaced all the cooling hoses, and any related parts (water pump, radiator, coolant overflow tank) you can flush the engine with clear water, allow it to drain, put the block plugs back in place and refill the system. The block plugs use the same copper sealing washer PN 102101 as the oil drain, and should be replaced as they are a wear item. A completely drained system will take about 4 US gallons of mixed coolant (15 liters). Bleed the thermostat and the top of the radiator, and check for leaks. If you have a pressure tester, pressurize the system and check for leaks on the hoses you just installed before you close it back up. 
Step 6 - (If you replaced the engine hoses) Reinstall the intake manifold. Connect the fuel lines and hoses. Recheck all your connections again. Start the engine and immediately inspect the fuel lines for leaks. Once you are satisfied that the fuel system is tight, run the engine long enough that the cooling fans cycle on and off several times. Monitor the temperature gauge during this process, as trapped air in the radiator or engine can cause an air lock and overheat the engine. If the gauge gets to the 220 degree mark, stop the engine immediately, allow it to cool, and re-bleed the thermostat and the radiator. 
By Dave Swingle 6/9/2016
Revised 1/13/2022 ET (formatting and links)