My '87 MR2 (4AGE) has been leaking coolant as of late so I decided to bite the proverbial bullet and change the water pump by myself. It's a good idea to flush the coolant system as well at this point in time. I ordered the new OEM water pump from toyotapartszone.com for about $90 (The stealership wanted to charge $120 for it!). You can purchase your water pump from the local auto parts store but it may not be OEM or as cheap as the one I scored. Anywhoo, here's a nice write-up of the painful procedure that is changing the water pump on a MKI MR2:
NOTE: You may want to change out your timing belt when doing the water pump (and vice versa), as removing the timing belt is only a few bolts away. (Albeit one of those bolts is the crank pulley's which can be a bear to get loose.)
**PARTS YOU'LL NEED**
Water pump, 2gal Toyota coolant Prestone Super Flush, Permatex Ultra Copper & Permatex Water pump and Thermostat Housing Gasket Maker), new alternator and AC belts (since you need to remove these too)
**Draining the old fluid**
1) First off, drain out as much old coolant as you can. Jack up the back of the car higher than the front, remove the front-most underbody cover (seven 10mm bolts), and remove either the drain bolts shown here, or use the draincock on the bottom of the radiator. I chose to use these 2 drain bolts, because my radiator draincock was plugged. Make sure to remove the radiator cap and also loosen the drain **** on the top of the radiator. This will allow air to vent into the pipes, allowing the coolant to drain out easier.
*NOTE: Dispose of the old coolant properly because it is highly-toxic to wildlife!*
--You can chose one of two routes here. Either flush out the system now, or go ahead and change out the pump. I decided to change out the pump next. Here's the procedure:
Removal of old water pump
1) Remove the 2 hoses circled below and remove the coolant reservoir by pulling it straight up.
2) To give you 'plenty' of room to get to the water pump, remove the radiator cap mounting tube. Do this by removing the spring clips (shown in the square box on the right and pointed to by the red arrow) clamping the hose to this plastic tube. Remove the two 10mm bolts shown in the green circles. Then remove the hose going from the radiator cap to the engine, by removing the spring cliip contained in the left red square.
Here's the result of the above removal. You can start to see the water pump now!
And here's the parts that you just removed:
3) Now, disconnect the 3 different wires (black, green, and blue connectors) that will be in your way and tuck them away someplace..
4) The next thing you should do is loosen (not remove) the water pump pulley bolts (four 10mm bolts shown in the red square). This is alot easier to do while the belt is still in place.
To get to all the bolts on the pump pulley you will have to turn the crank pulley. Do this by using a 17mm socket on the below circled bolt. To make this easier to turn it's best to remove the spark plugs. (I didn't do this however...) You have to remove the bottom engine cover (about seven 10mm bolts) to get to this easier.
4) Remove the alternator and it's adjustor bracket.
5) Remove the water pump pulley bolts that you loosened earlier and remove the pulley.
6) Remove the 'coolant inlet housing' located in the red square box (two 10mm bolts from the front and one 10mm bolt that needs to be removed from under the car).
7) Remove timing belt cover #3. Here's a pics of the cover removed to give you an idea of where all the 10mm bolts are located.
Here's a pic of the timing belt cover #3 removed.
8) If you have AC, remove the AC idle pulley. The below picture already has the belts off but it should give you an idea of where the pulley is located, between and above the crank and AC pulleys. Use a 14mm box end wrench to remove the nut from the pulley.
The red circle below shows where the 15mm bolt (it's a real long one) that holds the idle pulley bolt in place. Remove this bolt. The idle pulley should now be free, so remove it and the two belts.
9) There are only 2 bolts holding timing cover #2 on, since #3 is out. Get to them from below the car, and here are pics of where they are located:
Here's the one near the rear of the car, 10mm. (Ignore the fact that the new water pump is already in, I took the pics out of order.)
And here's the one on the other side of the crank. It's right behind the idle pulley bracket and is a pain to get to. I found a 10mm offset boxed wrench to do the job (luckily I had one).
10) Remove the water pump bolts. There are two 12mm bolts (red circles) & one 10mm bolt (green circle) that hold the complete housing to the engine block. And also there's 4 other 10mm bolts that hold the pump to the suction cover (not circled).
Remove the oil dipstick thingy, by pulling it straight out. Make sure to cover the hole with a rag or something. Once you are sure all the bolts are off, remove the water pump portion. It may take some pressure on it to remove it. I had quite a bit of coolant leakage here when I did this, since I didn't bother draining the engine block. So make sure to have your pan close by. (Note: Feel free to drain the engine block if you'd like to be a little neater than me. Consult the BGB for it's location.)
11) Remove the 2 below indicated 10mm bolts, which hold the suction cover to a coolant pipe. You can then easily remove the suction cover from the engine bay. Removal done!
**Installation of Water Pump**
1) Time to clean everything up (via Simple Green, WD40 & Carb Cleaner) and organize all the parts.
2) Permatex the 2 o-rings on the suction cover. Note: If you have removed the timing belt it is not necessary to put the suction cover and water pump on separately. You can bolt the 2 together, and then bolt the assembly to the block.
3) Loosen the coolant pipe by removing the 10 or 12mm bolt shown here, that leads from the suction cover to the thermostat housing:
4) Very carefully, place the suction cover onto the block and into this pipe. Make sure that the o-ring that attaches to the block didn't shift on you and that you still have some permatex back there. Secure (don't tighten) the cover to the coolant pipe, either from up top....
or below:
5) Permatex the water pump!
6) Very carefully, again, place the pump over the suction cover. Secure the pump to the cover by using a couple of the 10mm bolts to hold them together. Then line up the assembly with the block, and bolt it down with the 10mm (the longest one) and the 12mm bolts. (Note: The 10mm bolt for the assembly is for the uppermost hole.) Tighten down everything securely, according to the torque specs in the BGB, 9 & 11 ft-lbs I believe.
Also, don't forget to install the oil dipstick guide, since it attaches to the water pump. Put a lil RTV on its gasket.
7) At this point I would suggest to reinstall the coolant inlet housing onto the engine and then taking a break. This way after a couple hours of letting the RTV cure, you can check the water pump for leaks by simply filling the system with water. If you notice any leaks from simply filling it up, you will not have wasted time putting everything else back together. Use the new o-ring and gasket that came with the pump assembly when installing the inlet housing. Also, use some RTV on the surfaces.
8) Once you are sure that the pump isn't leaking, you may continue putting everything back on. Start with timing cover #2. Again, here are the 2 bolts that need to be replaced:
9) Next up is the AC idle pulley. Insert the bolt and it's washer (circled):
And then the pulley, 'big' washer, and the nut. Tighten the nut down until the pulley is secure, and then make sure the hole in the bolt head is aligned with the hole in the top of the bracket.
The red-circled hole.
Then, thread the long 15mm bolt through the idle pulley bolt. No need to tighten it down fully, just get the threads so they atleast pass all the way through the bolt head.
10) Next, install the water pump pulley and bolts. Don't worry about tightening the bolts for now.
11) Install the belts. Water pump and alternator belt go on the innermost crank pulley, then AC belt. Go ahead and tighten the AC belt, by pushing the idle pulley up while under the car. You may need to loosen the nut a little. I tried prying the pulley up with a big screwdriver, but the best method I found was just by pushing it up with your free hand, and then tightening the nut down with your other hand. Use one of them belt tensioner gauges (or index finger) to make sure the belt isn't too loose or too tight. Get out from under the car, and tighten down the AC idle pulley bolt (the long 15mm one).
12) Install the water inlet housing with new gaskets.
12) Re-install alternator. In the below pic, the above mentioned AC idle pulley bolt is shown in the red square. The green arrow is pointing to the alternator of course.
13) Reinstall Timing cover #3.
14) Reinstall radiator cap hardware and hose. Don't forget to reconnect those 3 wire connectors. Also ground the yellow/black wire onto the body through one of the green circled bolts.
15) And finally, the coolant reservoir:
16) Pat yourself on the back, crack open a cold one and proceed to brag to your significant other about how much cash money that you just saved by undertaking this challenging and potentially pricey maintenance job all by yourself!
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