Complete service manual instructions can be found here.  The MR2 has four drain plugs, one in the radiator, two in the piping underneath the car, and one in the engine block.  When I drain the coolant, I just remove the drain plug from the radiator, and let it drain.  Then I take a shop vac, and put the hose end into the filer neck in the engine compartment where the radiator cap goes.  I put the vac on reverse (blow) and blow the rest of the coolant out.  This seems to work well at removing the coolant.  I then siphon out the coolant from the overflow bottle.

Bleeding:

The car must be level for the bleeding to work correctly.  My garage floor is not level, but I can use a jack to jack up either the front or rear of the car to make the car level.  To bleed the cooling system, there are two bleeder valves that need to be opened.  They are both located in the front trunk.  One is on the radiator (driver’s side), and the other is on the heater core.  After removing the plastic covers, the radiator bleeder can be seen.

The heater core bleeder is shown in the following pictures.

Next up is to connect some clear hoses to each of the air bleeder valves.  The hose I use for the radiator air drain doesn’t fit quite right, so I use a worm drive clamp on the end of it to make a good seal.

The hoses have to be hung, in some manner, so that they are higher than the filler neck.

The valves can now be opened.  The radiator valve can be opened by hand, and the heater valve can be opened with a large flat screwdriver.  Both of them have to be opened about three turns for air to start to bleed through.  Coolant is added in the engine compartment filler (where the radiator cap goes), and is added until it starts to show up in the clear hoses up front.  Once all the air is removed (which can take some time), install the radiator cap until the first click.  It should still feel loose.  Start the engine and run it at varying RPMs (from 2000RPM to 3000RPM) with the heater all the way at hot for about 2 to 3 minutes.  By varying the RPM, hopefully, the air bubbles will be coaxed into moving to the higher location.  I’m not sure if leaving the air vents open during this stage, or closing them results in a better bleed – I’ve tried it both ways with success.  Re-open the radiator cap and add more coolant.  If you’ve closed the air bleeders, reopen them and check if more air is released.  If so, keep doing this until all the air is bled out.  The service manual just says to repeat these steps, but it’s a good idea to let the engine coolant cool down some between runs.  You may want to close everything up (leave the cap on the first click) and go for a very short drive, to try to jostle the air bubbles to the highest location, and then allow it to cool, and add more coolant.  Once all the air is out, fill the overflow bottle, and place the radiator cap on tightly.  You may want to fill the overflow slightly higher than the full line as excess coolant will just blow out anyway.  This would also be a good time to check the line running from the radiator cap to the overflow, and be sure it is clear/clean.
The overflow bottle can be cleaned without removing it.  I just fill it up with a degreaser (simple green / castrol / whatever), and water.  Let it soak, and then suck out the contents with a wet/dry vac.  Then rinse (or rinse&suck) a good number of times with clean water.  I do the same with the intercooler.
The following picture shows coolant in the air bleed hoses while filling.

Here’s the multimiter Pat used. Sourced from Sears tools section.

Here’s a pic of the probe in place under the inlet coolant pipe near the thermostat. Basically, you just move the clamp lower off the pipe, and lift up the hose with a blunt instrument, and wedge it under there. These 90 degree pliers and a flat head screwdriver were the only tools necessary.

Here’s the location of the outlet probe (not installed in this picture).

All temps indicated in degrees farenheit.

Regular Coolant Boiling Point = 255 degrees

NPG+ Boiling Point = 375 degrees
Estimate on stock temps with stock 180 thermostat

Inlet = 180

Outlet = 195
Regular Coolant temps with 160 degree thermostat (Pat’s car, normal driving).

Inlet = 160

Outlet = 175
Evans NPG+ coolant temps with 160 degree thermostat (Pat’s car, normal driving).

Inlet = 160

Outlet = 180 – 185 (This was on a 3 hour drive at 60 mph, temps would not go above or under these numbers)

Evan’s NPG+ coolant temps with 160 degree thermostat 70 degree outside temps (this is from Shane’s Car at Seattle International Raceway after race sessions)

Outlet 3 Hot Laps = 208

Outlet 10+ Hot Laps (20 min) = 228

After a few minutes with the engine off = 288 (exceeding normal Ethyl Glycol coolant boiling point by 25 degrees or so, thus the reason Turbo owners hear burping and gurgling after shutdown. This no longer happens when you switch to NPG+)

Description of HFH

The HFH is a simple 5 inch coolant hose on the MR2 Turbo that usually wears out and burts sometime after a car hits 100K miles. The symptoms of a bad HFH are low or no heat coming from the heater vents, water dripping under the engine near the exaust, and finally, a full burst will result in smoke clouds billowing out from under the engine compartment, and high temps. Sometimes people think they’ve blown a headgasket, but if you look under your car, and directly under the downpipe and exaust, there is water, it’s very likely to be the HFH. It is a major pain in the ass to fix without taking the exaust manifold off of the car, but it can be done in a few hours if you have patience, the right tools, and not overly large hands (borrow a kid from the neighboorhood to help!).

The HFH itself is made out of heavy duty rubber hose with a thin heat barrier shell with 3 outer clamps. The center clamp helps keep the heat barrier on and stop expansion of the hose, and the two clamps on each end hold the HFH to a metal coolant hose, one coming off of the Oil Cooler (which the oil filter bolts onto), and the other to a pipe called the Water Bypass Pipe that leads under the Exaust Manifold. It has a sister hose known as the Hose from Hell on Earth or HFHOE. The HFHOE connect to the Oil Cooler on the passenger side, and should be unclamped in order to remove the oil cooler for access to the regular HFH.

Cost of HFH replacement at the dealership = $300 thru $600+

Cost of fixing the HFH yourself = $5 (plus possible $5 – $30 in tool and replacement parts purchases)

BLAH

Pat actually did this back in early 2000 on his first MKIIT. He was originally going to show how to do this while the engine was still in the car with pictures, but after blowing his 1st motor, that plan is out the window, so we’ll have to stick to a description of the process.

DISCLAIMER

We do not recommend replacing the HFH and/or HFHOE unless you are determined, have small to medium hands, are able to work in awkward positions, have patience, are willing to buy any needed tools and parts that you don’t already have, and finally, ENJOY WORKING ON YOUR CARS!
We have to put a disclaimer on this one, because you can scrape/cut your hands, break or strip out parts, and possibly go insane! Please attempt this only if you are of sound mind and body, and of your own free will.

Required Tools

- A new Hose from Hell, Toyota Part # 16283-88381
- Normal and Small metric socket wrench and socket sets with mandatory 10mm and 12mm sockets. Extensions are also a must.
- Deep well 30mm Socket. This is for the Relief Valve on the Oil Cooler.
- Metric Open end wrench set.
- Long 90 degree bend needle nose pliers. These can be purchased from Sears Tool Department.
- Alot of towels, blankets, or drop cloths to protect your cars paint, since you will be leaning over the passenger side for a few hours.
- Gloves (heavy duty a definite, but small latex gloves will be very helpful as well).

Reccomended Extras

- New Oil Filter (Toyota brand of course!)
- New O-rings for the Oil Cooler, new gasket for the Water Bypass Pipe, and O-ring for the Oil Dipstick Tube.
- New Hose from Hell on Earth Toyota Part # 16282-88380
- Possible need of toys and candy to get the neighboorhood kid to do all the work for you

Procedure Part 0 “Pre-Op Study Pictures”

Study the pictures below, and at the bottom of this page to get familiar with the parts and their locations.
Picture #1, view from behind the Oil Cooler and HFH with Exaust Manifold missing, note the full oil cooler assembly (both top and bottom), with old hose from hell connected. Also note the oil dipstick tube and the spot that it plugs into the block.

Picture #2 and 3, here you can see where the HFHOE connects to the Oil Cooler Top. The wrench in the picture is connected by a 30mm Socket to the Relief Valve.

Picture #4, you can see the HFH next to the oil cooler. Note that the oil cooler top is not connected. You can clearly see the 4 bolts that hold the oil cooler bottom to the engine block.

Pictures #5 and 6, show the relation of the HFH and the exaust manifold. Note that the Turbo and Down Pipe are not connected.

Picture #7 Shows the view you would have looking from above. The Oil Cooler and general location of the HFH under the exaust manifold is highlighted. Note that the smaller heat shield and the dipstick tube have not been removed in this picture.

Procedure Part 1 “Getting to the HFH”

Tip1: You do not need to drain the coolant as the BGB specifies. You will drop a little when pulling the oil cooler off, but not that much really.
Tip2: Wear gloves!
Tip3: Put a towel over the trunk in front of the spoiler so you can place tools on it for easy reach.

1. Remove engine side covers, and place them in a safe spot.
2. Remove intercooler piping with 10mm socket, and plug ends with towels or socks to prevent debris from entering.
3. Remove Exaust Heat Shields with 12mm open end wrench. To get the smaller heat shield off, you must also remove the Oxygen Sensor (which is very easy with only two 12mm nuts securing it) If I remember right, there are 3 bolts on the main shield, and 211n the smaller downpipe shield. 1 on the main shield is hard to see, it is in the center near the bottom of the shield.
4. Remove the Oil Filter. I use a claw type tool bought from the local car supply store that works really well.
5. Remove Oil Dipstick Tube. There is one 12 or 14mm bolt on the top bracket. Once that is loose, you can pull the tube up, and it will pop up out of the block. Check to make sure the orange o-ring is at the base, and make sure it is not cracked or brittle.
6. Remove Relief Valve and Plate Washer from center of the oil cooler with the Deep Well 30mm Socket.
7. Remove the two nuts connecting the Oil Cooler Top to the HFH. Be careful to keep any o-rings and gaskets (there is a metal gasket inbetween the two nuts and the HFH pipe) connected to their proper parts, and I suggest placing all parts in plastic bags.
8. Remove the HFHOE from the Oil Cooler Top by removing the clip.
9. Remove the Lower Oil Cooler Half by removing the 4 10mm bolts with the socket wrench and extension. Look for the 2 o-rings at the base.

Procedure Part 2 “Swapping out the old one for the new one”

Now you are at the difficult part. Take some deep breaths. Do some Yoga and stretches, especially your right arm and hand. Wear a latex glove if possible. For the next bit, you have to use your sense of touch alone.
1. Reach in there, and feel around for the HFH under the exaust manifold. It should be easy to find. Try to find all three clamps. It is possible the part of the HFH came off when you pulled the Oil Cooler out, so there may be a missing clamp or two. If you have all three, you can use the 90 degree nose Pliers to pull the one closest to you off. This will allow the small pipe section to come out. An alternative is to use some snips or tough scissors, and cut the HFH in half just to get this pipe and excess hose out so you can work.
2. Find the furthest clamp with your hand. Note the orientation of the prongs. If you’re lucky, they will be facing a direction which will allow you to use the Pliers, and it will come off in 10 seconds. But, if not, you will have to give it a few tries, and may have to turn the clamp to face a better position. You may want to use the pliers on the inside of the hose to open up the hose, and break the seal that it has. Then use the pliers to turn the hose and clamp, or possibly your hand (with heavy glove) and then use the pliers to grab the prongs, and pull it out of there. At one point, I used a razorblade to slice up the hose to turn the thing around, but I would only do that as a last resort. Note: Without the 90 degree pliers, I spent 4 hours trying to get the last clamp off with regular tools, and could not do it. It took maybe 10 seconds with the 90 degree pliers!
3. Once off, you can now grease up the pipes and new HFH and HFHOE ends with some engine oil, then pop the old Water Bypass Pipe on there (do not remove the prong clips yet), and put it back in place under the exaust. It may take a minute to get it on even with the engine oil. Now orientate the HFH so that it’s easy to get at the prong clips with the pliers, and get the pipe that connects to the Oil Cooler with two nuts aiming the correct way. Now use the pliers to remove the prong clips. (Do not use your fingers, as those clips prongs have a lot of stored energy, and can slice through skin like butter. (don’t ask how I know that)

Procedure Part 3 “Putting things back together”

1. Examine the Oil Cooler and Relief Valve, look for obvious damage to threads and blocked passageways. Replace any o-rings that you purchased. (lube them with a little engine oil)
2. Reattatch the Oil Cooler bracket/bottom to the block, and tighten the four nuts to 69 “inch” lbs.
3. Put the Oil Cooler top in position and connect the HFHOE (this may take a few minutes, don’t get frustrated, take a break and come back if it’s taking too long), also “loosely” connect the Water Bypass Pipe with the two nuts (don’t forget the metal gasket). Do not tighten it, you want it to have the ability to flex a bit.
4. Put some engine oil on the Relief Valve threads and tip. Lean over and look to make sure you can align the Oil Cooler top with the bottom. This is very important, and hard to do because the two hoses are fighting to put the Oil Cooler Top in a different position. Align them up, and then put the Relief Valve in place, and hand tighten. If it didn’t feel right going in, loosen it, and check for any damaged threads, if there are none, then it was probably ok, if there are some, clean them off, since this was only hand tight, the damage is small, and you can try again. When it’s going on correctly, tighten it down to 58 foot lbs. Do not overtighten, and if it feels funny, back it out, and check the threads for damage.
5. Tighten the two Water Bypass Pipe nuts to 69 “inch” lbs.
6. Reinstall the Oil Dipstick Tube by placing the bottom of the tube with the o-ring back in the block first then aligning the top bracket up with the water inlet and replacing the top 12mm bolt. (don’t drop it!)
7. Lube up the new oil filter bottom gasket with a drop of engine oil, and hand tighten.
8. Replace the heat shields and bolts.
9. Replace the intercooler pipes and clamps.
10. Replace the engine side vents and screws/bolts/zip ties, whatever you use.

Procedure Part 4 “Aftermath”

Check coolant level, fill as neccessary. Check oil for the heck of it. Start the car up, let it run for a minute or until the temp gauge goes over halfway. Let it cool down, and then fill the coolant again. Repeat as many times as it takes for the car to not overheat. Don’t worry about violent gurgling coming from the surge tank. This is normal during a filling procedure.
Once you’re sure the coolant is back to normal, drive it for a few minutes, and pay attention to your temp gauge. If it goes over the half way mark, just pull over, and let the car cool down for 10 minutes or so. Add some coolant, and continue.

Finally, if you have a comment/question/suggestion/correction, please e-mail me us!

Below are some pictures and descriptions to go along with the replacement procedure

Here are pictures from the 95 BGB on how to perform this task. You can use these pictures to replace the hose, or use them as a supplement to this document. The HFH is colored red in the first picture, and the white part in the middle is one of the three clamps (why the other two are not pictured, I don’t know).

In order to switch from regular antifreeze/water (Ethyl Glycol system) to a non aqueous NPG+ (Propylene Glycol system), you must get rid of 100% of the H20 in the old system. In order to do this we decided to flush the system out 2 times, first wih Sierra brand coolant (Proplyene Glycol also) to flush out the old antifreeze/water, and second use the NPG+ to flush out the Sierra. You can get Sierra from most auto parts stores. We reccomend 4 gallons, so you have a little left over in case of a spill, or a leak, etc. Also please note that you need to run NPG+ with a 160 degree thermostat in order to have temperatures that are close to stock. See this page for more info Water Temp Testing 

“LET’S GET READY TO RUMBLE!”  

1st, source the 2 service hoses from behind the spare tire rear cover. These should be in your car, if not, go and get a few feet of hose from a Home Depot type store.  

The 1st hose goes on the Radiator service valve.  

We used tape to hold it vertical.  

The 2nd hose goes on the heater core system service valve. Suspend it just like the 1st hose.  

Your car should look a little like this.  

Drain coolant: 1st, pull the pressure cap off in the engine bay to allow the coolant to flow more easily. Now, reach under the car near the passenger side of the radiator facing forward. Place any type of hose over the radiator drain, and unscrew the valve with your thumb and strongest finger, and drain the coolant into a garbage bag lined bucket, or other safe coolant storage sytem.  

Now, it’s time to undo the two service hose valves. Loosen the 1st valve (radiator top) with your hand until coolant begins to run up the service hose. The 2nd valve can be opened by turning the white plastic knob with a broad flathead screwdriver. Turn it as the 1st one until coolant rises up the hose. Leave them both open until the entire flush procedure is complete.  

Now, jack the rear of the car up pretty high to make your life easier. Be safe and use jackstands.  

Looks like it’s doing a kickout to me.  

Underneath the car, remove the mid rear plastic under carriage cover. Their are a few 10mm bolts and one nut.  

Here are the two 12mm mid system drains. Place the bucket under them, and we reccomend you wear eye protection, and close your mouth as you loosen each  

Finally, underneath the engine, there is a 14mm drain bolt. It is located underneath the turbo VSV (you know, the thing you plugged to get your boost controller to work!)  

Now we are ready to flush the heater core system. This is vital for a complete system flush. To make things easier, we suggest you pull your intake off near the turbo.  

Remember to remove the connector from the AFM at the clip, and not the two screws, otherwise you’ll be destroying an expensive ($750?) piece of hardware.  

Now would be a great time to clean or replace your filter.  It’s time to flush the heater core, first, close the heatercore service valve up front to allow pressure from your gravity flush to push coolant out of the heater. With the intake removed from the previous step, you can now can get at the two heater system hoses. Inlet and outlet. To pop these guys off, you may have to resort to yelling at the car (it is tough). That seems to be an important part of this step. We used flathead screwdrivers and Pat’s favorite tool, the 90 degree bend large pliers. FUN!  

We recommend you use a system similar to this to flush the heater core. We used an old oil filler cup and ran the hose into the top of 2 heater core hoses, and let the bottom one drain into the bucket.  

Another angle. We used about 3/4 of a gallon of coolant to flush this system. You can tell when you’re done by watching the color of the fluid coming out of the lower hose. Once it changes color completely, you’re done flushing. When done, reattatch the hoses. Make sure to open up the heater core service valve up front now.  

It’s a good idea to make sure your overflow bottle is empty. We used a cheap bottle pump from the local auto parts store.  

Cheerios in the bucket are necessary to keep the coolant from eating through the plastic………… Just joking!  

Once done, we decided to modify the overflow bottle cap like this to ensure no water is pulled back into the new NPG+ System.  

This step is not necessary if you are just flushing your system with regular coolant. All we did was remove the center hose that goes into the bottle.
At this point, it’s time to get ready to fill the system up. Get under the car, and put the 14mm engine drain bolt back in. Move to the middle, and put the to 12mm middle system bolts in. Move up front, and tighten up the radiator drain valve. Leave the service hoses open to the air.

Remove the pressure cap, and begin filling. Watch the top of the system for overflow. It will happen, as the system fills very slowly, and backs up from time to time. Once the hoses up front are to the level of the rear pressure cap you can put the cap back on, and start up the car. Let it run for a few minutes until the temp gauge starts to rise. Turn the car off, check for leaks, and look at the level of the service hoses. If they are low, add more coolant. Repeat this a few times until the system won’t take any more. You may now want to take a short drive to verify stability, just keep one eye on the temp gauge. If it goes above half way, their is a problem, since the 3SGTE will never read above half way unless their is something very wrong. “Don’t forget to bring a towel”, and a your tools and a bottle of coolant.  

Properly filled system.  

Take another drive to your local auto store, and drop off the coolant. Call ahead first, as not all stores can dispose of coolant.  

Time for a bath!  

SWEET!