Sam-Q's 20V RWD Cooling System Guide

[Sam_Q]

I decided to post the whole guide on there so people can always view it, please notify me of any corrections/aditions/changes to be made.



http://i127.photobucket.com/albums/p143/daunderdweller/signiture.jpg


http://i127.photobucket.com/albums/p143/daunderdweller/mesprinter.jpg




Sam-Q's 20V RWD Cooling System Guide


With many different stories on how to convert a 20V engine into rear wheel drive form it seems that many people are under the false impression that water cross-over pipes are needed or even worse firewall modifications are necessary to make it work. Another article shows a way to avoid the cross-over pipes but requires a hole drilled into the head. This article is to show how to make a custom RWD cooling system that looks factory, works as well as factory, doesn't promote any air locks, doesn't have any extra external main pipes on the side of the engine, uses a completely standard engine (no drilled holes into the head), can keep the heater working and most of all no modifications to the body of the car such as the firewall.


When I did this conversion I tried as much as possible to make everything looking as original as possible. While this is very hard to do with any engine conversion it is however possible if done right.



Water Pump modifications:


Remove the old water pump assembly and the top cast aluminum fitting, you will need to take the front timing belt belt cover off to do so. You should end up with this:

http://i127.photobucket.com/albums/p143/daunderdweller/20vcooling/barefront.jpg



For the cooling system to work the rear half of 4Ac single cam pump is needed. I found a spare pump sitting in my back yard in the weather, it had been there for many years, needless to say time hasn't treated it well. I cleaned it up later with some acid based mag wheel cleaner which worked wonders. Heres it alongside the 20V one, notice how the 20V one has no provision for a thermostat (left):

http://i127.photobucket.com/albums/p143/daunderdweller/20vcooling/2pumps.jpg



While a 4Ac pump will fit straight on the 20V engine it in it's normal form is of no use. This is because even once the pulley is swapped from the 20V the spacing is wrong. Here is how it alings when this is done:

http://i127.photobucket.com/albums/p143/daunderdweller/20vcooling/thermopulley.jpg



Notice how it sits too far forward to be aligned correctly. I have been told that using a pulley off a JDM RWD 4AGE 16V will correct this I prefer using what is already available. For this I used the front half of the 20V pump and the rear housing of the 4Ac pump. These however are not a direct fit. Looking at the two it's obvious that they are different:

http://i127.photobucket.com/albums/p143/daunderdweller/20vcooling/2pumpsinside.jpg



The 20V has one additional impeller blade and also has slightly higher blades than a 4Ac and therefore wont clear a 4Ac rear housing. The front half of the 20V can be made to fit though with a simple mod. For this I unbolted the pulley off the 20V front and carefully clamped it in a vice so as to face the blades upwards. From here is very carefully ground down the impeller blades about 1.5mm with a grinder. For this one slip can mean the end of the seal on the housing so I highly recommend having a person help by holding something like a piece of metal under the grinder wheel on the housing. This is so if the grinding wheel slips (trust me it's real easy) then it will hit the steel instead of the fragile aluminum housing. Whenever a piece is ground off do it evenly to all 7 blades in small intervals and then check it every time. For this just grab the housing and place it into the rear housing without the gasket. Once it turns freely throughout it's rotation then it is complete. If it is checked without the gasket in place then it will allow for extra fitting tolerances when the gasket is reinstalled. Here is how mine looked when the grinding was completed:

http://i127.photobucket.com/albums/p143/daunderdweller/20vcooling/blades.jpg




Now the rear housing needs to be modified for the rear water bypass. In its normal form on the 4Ac engine the top water outlet on the engine holds the water bypass pipe in place in the rear pump housing. This is as shown:

http://i127.photobucket.com/albums/p143/daunderdweller/20vcooling/oldpipe.jpg

This pipe has an O-ring on the end of it to seal it (well known for leaking). Once installed on a 20V the pipe is still needed however it needs to hold itself in, be shorter and also be on an angle to suit the custom top outlet. The most professional way of doing this would be to machine an aluminum pipe of the correct size and get it Tig welded in place. I chose the easier option here and made something out of steel. For this I cut the straight part of the steel pipe off the 4Ac top outlet pipe. I machined up a short section with some grooves in it for sealing (very optional), chopped the original pipe just above where it sticks out of the housing and then welded on my machined section on a angle. It turned out as shown, notice the groove left by the removed O-ring at one end:

http://i127.photobucket.com/albums/p143/daunderdweller/20vcooling/bypasspipe.jpg



This needs to be held in somehow into the original place on the rear housing. For this I chose an epoxy resin. A word of warning though, I used a normal epoxy resin, these are rated at a max continuous use of only about 60 degrees, this is well bellow that of the cooling systems running tempreture. A high tempreture epoxy must be used, I now have my pipe leaking due to the heat fatigue and need to find a way of repairing it, don't make the same mistake! A product that should do the job well is Quicksteel, I will use this when I do my repair. Also when gluing in the pipe be very carefully to make sure that it is in fact in the right place and facing the right direction. If it is wrong it would be extremely difficult to change. A test fit on the engine and then marked out is the only sure fire way.

Here is what my housing looked like when it was complete:

http://i127.photobucket.com/albums/p143/daunderdweller/20vcooling/pump2.jpg

[Sam_Q]

After this is all done the rear half of the housing can be bolted to the 20V front using the steel gasket of the 20V and then bolted to the engine. Seeing the front housing is slightly different it will be slightly off matching the cover of the 20V. While it will still fit it is slightly different but it is very minimal. Here is how mine looked all bolted up:

http://i127.photobucket.com/albums/p143/daunderdweller/20vcooling/pump.jpg



Off the rear of the standard water pump is another pipe that is needed. It normally is bolted to the back and goes under the manifold and to a rubber hose at the end. This isn't a straight swap as it fouls the knock sensor and quite possibly the manifold brace also. The easiest way around this is to just chop it off approximetly 40mm away from the flange. With this cut the rubber hose can still be used for rest of the chopped section, more on this later. I however chose to chop and re weld the pipe on a different angle, I also had to make a new bracket at the end to support the pipe and it worked out well (got lucky!). I ground and painted mine to make it look as close to factory as possible. I was quite happy with how it turned out:

http://i127.photobucket.com/albums/p143/daunderdweller/20vcooling/pipe3.jpg
http://i127.photobucket.com/albums/p143/daunderdweller/20vcooling/sidepipe.jpg


After all this is fitted it brings up the last problem of the new water pump placement; with the new position the top the bottom radiator inlet directly fouls against the alternator as shown in this picture:

http://i127.photobucket.com/albums/p143/daunderdweller/20vcooling/altandcooling.jpg



By far the easiest way to get around this is to just combine two tensioners and then angle the alternator far enough away that a radiator hose with a sharp 90 degree bend in there can fit onto the outlet. I chose the most difficult option (when don't I?) and made a new custom bracket that holds the alternator low on the other side of the engine. I wouldn't recommend this option at all because it is very difficult to make, difficult to get right, can have some very bad effects if slightly out, etc... It does however place the alternator close to the battery, in a very convenient place. Also of note since I am running no air-con and my custom mount has a traditional tensioner I managed to discard all the original engine tensioners which are heavy, difficult to work with and always seem to seize up. I used a modified Corona tensioner which pivoted off a bracket that bolted to my first extractor bolt. I think for the average person who wants to move the alternator to the other side then what I did is still a bad idea. I would instead say a mount of another 4A based engine such as a 4AFE, etc.. a 4Ac bracket might even fit.




That's it for the water pump, it can now be bolted up and left alone. To fit the pump to the block the original metal gasket from the 20V block can be used..






Custom Top Water Pipe:


With the new water pump setup in place it leaves the top water inlet of the head exposed. While this previously received water directly from the water pump it needs to be changed to be an water inlet from the radiator. Some people have cut the original fitting and re welded the aluminum to face forwards. While this is a potentially good approach it must be kept in mind that any pipe made that goes first down then up encourages an air-lock in the cooling system is therefore is unrecommended. The easiest option I have seen is to cut it off almost at the flange, weld the very end of the pipe (with the barbed end) onto the flange and then fit a radiator pipe with a sharp 90 degree bend onto it, much like what can be done with the bottom pipe. Another easy way is to cut a flange and just weld a piece of pipe in on an angle, this is very effective and simple enough. I chose the hard option once again and made something that uses all of the opening and is of a smooth and contoured design to maximise flow. I firstly copied the original and made a flange with the oval opening in the middle. From here I welded together a stainless bend to the flange with an additional section to divert the flow through the entire opening, then I welded on a straight stainless section with grooves cut into it for sealing. Initially I though this was all it had to look like and so it looked like this:

http://i127.photobucket.com/albums/p143/daunderdweller/20vcooling/pipe.jpg



It was at this point however when I found that I had to add the provision for the bypass pipe, So my top pipe ended up looking like this:

http://i127.photobucket.com/albums/p143/daunderdweller/20vcooling/pipe2.jpg



This bypass pipe needs to face the outlet that is glued into the water pump. There needs to be room to fit the rubber pipe and the two hose clamps that are needed. I also decided to add a dip-stick mount and also the engine temp sensors to it (more on these later). Here is mine fitted to the engine without the rubber pipe in place, also in the second picture drawn in place is where the rubber hose is needed to be fitted. I left enough room so that I could bolt everything in place and then fit the rubber hose by bending it and putting it in place later.

http://i127.photobucket.com/albums/p143/daunderdweller/20vcooling/outlet.jpg
http://i127.photobucket.com/albums/p143/daunderdweller/20vcooling/side2.jpg



The finished setup should end up looking something like this:

http://i127.photobucket.com/albums/p143/daunderdweller/20vcooling/final.jpg




Dip-Stick:


As shown by the top picture I made a bracket off the water pump to hold the original 20V dip-stick in place. I have however been told that a 4Ac dipstick can be directly fitted instead. I decided to make the mount to use the original 20V item as it is a much nicer model and also it gives me piece of mind that it's right, even if it is highly unlikely that the 4Ac model has a different length. If a custom mount is made be sure to check that the dip-stick can be taken in and out easily. I initially had some problems with a position I was testing in that the dip-stick would snag against something on insertion because the dip-stick tube was on an angle. Also check that it isn't held too close to the water pump pulley, I moved mine further way that was was necessary because I plan to fit a larger water pump pulley later for an under-drive.






Rear Bypass Plate:


While one other 20V RWD guide suggests drilling a hole in the back of the head I think this is a bit much and risky, it also might cause a limitation in flow and also makes it impossible to use the engine in Front Wheel Drive form ever again. Instead a better way in my personal opinion is to have an external bypass. Firstly unbolt everything off the back of the 20V head and throw it in the bin, it isn't needed. After the head is stripped looking at the back reveals two holes for cooling and three threaded blank holes for mounting.A thick plate needs to be made that can comftabely cover these outlets and be held in place by the three threaded holes. A thickness of about 20mm is ideal and aluminum is highly recommended. I had a threaded hole in the middle of my plate for a temprature sensor, this is the hole in the middle, ignore this as it isn't part of the mounting, heres how it looked:

http://i127.photobucket.com/albums/p143/daunderdweller/20vcooling/rearplate3.jpg


more below ....

[Sam_Q]

Now a slot needs to be cut into this plate, The slot needs to be there to flow from one outlet to the other. While I used a milling machine which is the recommended way it would be in possible to do it other ways. It would be possible to do it with a die grinder and an aluminum cut carbide burr. Also potentially possible but unrecommended is with the careful use of a grinder and a grinding wheel intended for aluminum, don't use a normal grinding wheel!! The picture below is mine seemingly finished, I later changed my mind on having a temp sensor mounted in the middle and instead chose to plug the hole up.

http://i127.photobucket.com/albums/p143/daunderdweller/20vcooling/waterplate.jpg



Lastly when this is made it's a very good idea to leave the two threaded holes above this alone and very free, these I recommend to be used for an engine mount.






Side outlet:

On the exhaust side of the engine to the right of the exhaust flange is an outlet that normally has a radiator hose fitting on it. Take this off but keep the gasket. Make a plate up that covers this hose and if no heater is going to be used then bolt it back up with the gasket to just block it off. However if you are like myself and want to keep the use of the heater then this needs to have a small outlet placed into the middle of it to go to the heater core water flow control valve (next to clutch master cylinder). It needs to look like so:

http://i127.photobucket.com/albums/p143/daunderdweller/20vcooling/sideoutlet.jpg



Heater hoses:

To get the heater working again various heater hoses need to be fitted. For this hose joiners need to be used, I bought a brass item from Super Cheap Auto but I have seen an ever cheaper plastic product with two included hose clamps from a Service station sold as an emergency repair kit but I wouldn't trust it long term.

Here is the final layout as it is installed, keeping in mind that this engine had no transmission on it at the time and so it was tilted forward. Normally it would lean significantly further back and have the distributor base almost touching the heater core hose.

http://i127.photobucket.com/albums/p143/daunderdweller/20vcooling/hoses.jpg



Firstly both of the original heater core hoses are kept, although one may need to be lengthened. Also before the engine is installed one pipe should be cable tied to the metal lines behind it when it goes near to the distributor base, it should be made to fit as close as possible to the firewall for clearance reasons (See above picture: pipe #3). The rest of the pipe is fine in the factory position and will not interfere.

The other heater core pipe it is the hose that goes from the heater core on the firewall then across and down to next the block on the drivers side (See above picture: pipe #2) . If the pipe is kept close to the original layout as it was on the single cam then it will fit straight on. Otherwise if only a small section of metal pipe was kept on the rear of the thermostat housing then a simple joiner and a straight section of heater hose will be just as good. I wouldn't at all recommend running a new straight water hose all the way to the heater core as the original can hug the body very close which is exactly what is wanted with a 20V install.

The last pipe is a totally unique item and no off the shelf part can fit, it goes from the outlet on the side of the head to the heater core flow control valve. (See second picture below. For this I used a heater hose intended for a Gemini, I chopped it in the middle, added the joiner, rotated it on the join 180 degrees, clamped it back up and then cut a short section off one end. The picture below shows what it needs to look like and where the hose joiner can be added.




It will need to be fitted as shown bellow




With these pipes in place the heater should just as well as it did before the conversion.



That's it!

I am still working on this guide and will continue to edit it, so if there are any suggestions or corrections then I want to hear it. I want people to know how to do this to curb the horrific 20V installs and misconceptions that are so common. If you have a picture that you think might be of help if it is added then please contact me.


For all questions please let me know at:

daunderdweller @ hotmail.com (remove spaces)

which is also my MSN instant messaging account


or just send me a friendly PM

[Steve-AE86]

damn, you do a lot of shit the hard way :P

4age rwd water pump housing fits the 20v front half without grinding impellers etc, and is only about $50 from toyota...

there's actually a guy in queensland or nsw somewhere that makes a full alloy kit to do the outlets/bypasses for around $150 or so. it also looks neat, and factory.

+rep for effort tho :)

[Sam_Q]

yes I have heard that it would fit but I never had it confirmed, would you happen to have a part number for that Steve?

I beleive the kit is from Anthony Kellam, he chose to use an external thermostat which I find odd but I do beleive it requires less fabrication than the way I have done things.

[Steve-AE86]

nope, not his kit.

this one uses the 4age rwd thermostat setup. (also sold seperately from mattel)

the kit fits perfectly, everything lines up. the rear bypass plate looks similar to yours, but with the addition of another threaded hole for the temp gauge, as well as the coolant temp sensor.

the plate behind the extractors is purely a blockoff.

the top bypass outlet on the water pump gets blocked off (alloy bung welded in), and it uses a t-piece to heat up the thermostat, off the top hose, from memory.

all in all, it's a nice kit, and looks VERY neat.

i've used 2 or 3 of them now, in my shop, when doing 20v conversions into rwd cars.

also, i've used alternator brackets from rwd 4age's to overcome the alternator placement issue. this also allows the use of a fwd thermostat housing(the one which bolts to rwd waterpump). basically it's a longer outlet, but it has a thermo switch in it, which is excellent for triggering therm fans ;)

[Sam_Q]

souns great steve, do you have some pics?

[Steve-AE86]

currently, no, sorry. next time i buy one, i'll post up some pics tho.

[Sam_Q]

guide updated, all the dead pictures fixed up

[30psi 4agte]

well put together thread mate! Full credit to you for taking the time to detail each step with pics and a speal.

+ rep

[Grega]

rep up sam. nice one
what did you do with your alternator?

[DX20VT]

( edited, double posted)

[DX20VT]

also, i've used alternator brackets from rwd 4age's to overcome the alternator placement issue. this also allows the use of a fwd thermostat housing(the one which bolts to rwd waterpump). basically it's a longer outlet, but it has a thermo switch in it, which is excellent for triggering therm fans ;)

Buy using the correct bits and pieces of other models it certainly saves some time and hassles.

I looked at doing this to my car, and for a road car I probably would,

and I dont mean to pick hole in the way you do things but...

The way the water flows through the standard 20V head, the cold water is drawn in from the radiator into the back of the head and along the passage past all the intake ports and then out the side of the head and into the back of the water pump.

This means that the coldest water available is run directly past all the 4 intake ports to keep the intke side of the head colder to reduce the heating of the intake air.

The way you have it setup it now becomes the hotest part of the water system.

It seems weird that toyota designed the water to go into the back of the head then along the head and then straight back out again, where in the older models they run the steel water pipe off the back of the pump externally along the block.

Weather it has a great affect on the actual intake air as it goes past the ports or not I cannot prove, but it may heat the intake air up which will loose power, and may help create detonation, and when you are chasing Hp out of an engine it may be worth thinking about.........................

[Sam_Q]

Grega: I made my own mount, I can show you some pictures if you like

DX20VT: yeah its an interesting point that I have thought about before, I also don't know if it would make much of a difference. Toyota seems to have designed quite a decent cavity above the intakes and it is sad that this potentialy well thought out design feature is now possibly a negative instead. I do know that if it meant I would have a couple of kw less power to not have cross-over pipes then I would still have what I have now. Also of note what I have now is almost identical to a 16V, and i figure if its good enough for the Group A guys it will do for me.

[Grega]

Sam, is AOK, I found it in your other link :)