Tech:Engine/A Series/Cooling Guide
A front wheel drive (FWD) 4A-GE water pump off either an AE82 or AE92/3 is fundamentally different from a rear wheel drive (RWD) 4A-GE pump from a JDM AE86. To begin with, the RWD pump is taller than the FWD pump (i.e. Sticks out further from the engine block). The RWD pump also has better bearings in order to support the weight of a pump mounted radiator fan. Note: If you attach a fan to the front of a FWD pump it will soon fail and no longer function. Interestingly, a RWD 4A-C water pump is almost identical to that of a RWD 4A-GE pump. The only difference is the position of the little ridge on which the cam cover sits.
Water Pump Rear Housing:
Once again the FWD variety of the 4A-GE rear housing is very different to the RWD version. It consists of only a single large water inlet (from thermostat) and an outlet which bolts directly onto the front of the 4A-GE block. The RWD version on the other hand has in integrated thermostat just after the water inlet as well as a bypass inlet from the front water outlet on the head. There is also another inlet which comes from the heater core and had the same outlet bolted onto the block. The RWD 4A-C rear housing is identical to that of a RWD 4A-GE one.
A FWD 4A-GE has a pulley with a smaller offset than the RWD 4A-GE one in order to compensate for the shortness of the FWD water pump. The RWD 4A-GE one is considerably more offset. The RWD 4A-C version has the same offset as the RWD 4A-GE one but it uses a single V belt rather than a 5-rib belt.
Front Water Outlet from Head:
Both FWD and RWD 4A-GE versions have outlets that point forward from the front of the motor but on the RWD version there is a short bypass pipe which goes directly down into the back of the water pump rear housing. On the FWD version a small bypass pipe runs down the length of the block to a remote thermostat. A RWD 4A-C has a short outlet which points out perpendicular to the length of the engine and a bypass pipe slightly longer than the RWD 4A-GE version which goes into the water pump rear water housing.
Rear Water Pipes: (From the back of the water pump rear housing)
As mentioned before, The FWD 4A-GE has a large inlet pipe coming from the remote thermostat. The RWD 4A-GE system has one main pipe which comes from the heater core, It also has some smaller pipes which direct water into the throttle body. The RWD 4A-C pipe is just a single return from the heater core.
Rear Water Outlet from Head:
There are 2 different FWD versions of this outlet the AE92/3 4A-GE has a pipe which protrudes out further from the block than the AE82 4A-GE version. The RWD version from an AE86 4A-GE is very similar to the outlet from an AE82 4A-GE except the outlet pipe is longer and has another small pipe coming off it for the throttle body. The RWD 4A-C one is not at all similar to any 4A-GE version.
As mentioned before the RWD 4A-GE pump housing rear has a thermostat integrated, again this is similar but not exactly the same as the RWD 4A-C one, it isn't really ideal to use on the RWD 4A-GE setup. The small inlet pipe from the radiator does not have any provision for a temp sensor and is the same for both RWD 4A-C and 4A-GE. The thermostat for a FWD motor on the other hand is different, it is in its own remotely located housing, there are 2 different types, one from an AE82 and the other from the AE92/3. They are fairly similar and both have provision for a temp sensor on the inlet.
There are 2 main different types of alternator bracket for the 4A-GE the FWD one bolts on at the bottom of the block and sits the alternator relatively high. And adjuster strap is mounted to the front water outlet from the head. The RWD one on the other hand bolts to the same place but sits the alternator lower and has an adjuster strap mount on itself. It also has one extra bolt, sitting on top of the RWD engine mount. Why does this matter? You cannot run a RWD water pump and rear housing without it, otherwise the inlet will be blocked by the alternator.
RWD Harmonic Balancers are different to the FWD AE92 version. The inner part of the pulley has a greater diameter on the RWD version. What this means it that the alternator will more than likely be pulled closer to the block on a RWD engine but I can confirm that the standard AE92 4AGE harmonic balancer works just fine with the RWD alternator bracket and strap.
RWD Water System on a Smallport 4A-GE
As some may already know, you cannot use RWD 4AGE heater return on a 4AGE with a knock sensor (small port, GZE etc). I devised another plan which was to use the heater return off the 4AC RWD and twist it 180 so that it sat off the block and also sat lower than the sensor. Here are a couple of photos to explain.
You can see here the small amount I had to lop off to make the pipe fit in (otherwise it just goes straight into the sandwich plate). I cut up an old battery strap to make a mount for the pipe and it works brilliantly:
Shown is the incorrect connection of the heater water line, if a heater is not being used both ends should be plugged not connected together as shown above. This above water make an effective radiator bypass.
Can you use a RWD 4A-C water pump on a RWD 4AGE? Yes, you just need to file off a little of the timing cover ridge and you must also use a RWD rear pump housing too.
Can the RWD 4A-GE rear water pipes be used on a Small Port 4A-GE (100kw) motor? No, unfortunately they cannot, they interfere with the knock sensor on the block. (Work-around in the next section)
Can the RWD 4A-C rear water pipe be used on a RWD 4A-GE? Yes, it can, but it wont allow you to run the throttle body cooling. Same problem as with the 4A-GE pipes on the Small Port in standard configuration also.
Is there any way to keep the FWD alternator bracket when using a RWD water system? Maybe, but it’ll require some modification of either the thermostat input pipe or the bracket itself.
How can I incorporate a temperature sensor (for a thermo fan etc) into my RWD water setup? By using one of the thermostat inlets from the remote thermostats of either the AE82 or AE92 you can use the inlet pipe in place of the regular one which has a temp switch built in.
Can I use a FWD pulley on the RWD water pump? No, if you do the belts will not line up.
Do I need the proper RWD head rear water outlet to run the RWD water system? Yes, unless you do not wish to use the throttle body cooling part.
Can I use the front water outlet pipe on the head of a RWD 4A-C on a RWD 4A-GE instead? No, it will not bolt onto the 4A-GE head.
Can the bypass pipe leading from the front water oulet to the rear pump housing of a RWD 4A-C be used on a RWD 4A-GE setup? No, but it would probably be possible to shortern it to fit.
- http://www.rollaclub.com/board/index.php?showtopic=19896 (Discussion On 16V 4AGE Cooling On Forum).
Article by Golberg
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