4AG gurus, confirm my alternator/water pump questions?: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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Jan. 6, 2010 10:18 p.m. ae86andkp61 Reader

Some of you may have been following my RWD Corolla project:

http://grassrootsmotorsports.com/reader-rides/170/

If not, the short version is that I have an AE86 and am nearing completion of a new 4A-GE which will be installed soon. The engine started life in an MR2, the previous owner converted it to longitudinal mounting, built the bottom end, and ported the head. It used to have a singlecam 4A-C cooling setup and alternator on the twincam block. I am trying to make it more of a standard RWD 4AG setup, and have lots of 4A-G parts, but as always, the parts which are FR and twincam specific are the toughest to find. I have switched over to the correct RWD twincam alternator bracket (on the intake side) and am also switching to a different thermostat housing to clear the alternator.

Right now I have a FWD AE92 GT-S thermostat housing, which just clears the alternator and fits the back half of the water pump fine. My understanding is that it uses the same thermostat as RWD, but with an o-ring instead of a paper gasket, correct? I ask because the thermostat is no longer a snug fit in a shallow depression, but a loose fit in a larger, deeper hole. I can get a new thermostat if need be, but the info I have found online seems to indicate that the thermostats are the same....but the thermostat seems loose in the housing. Can anyone confirm?

2nd question: Are the AW11 MR2 and AE86 GT-S alternators are the same? I know that they mount differently in the two cars, but I have an MR2 alternator and holding it up, it looks like it should fit the AE86 bracket, belt, and plug. I will probably try to run it unless someone gives me compelling reason not to. The engine now has the correct RWD twincam water pump, water pump pulley, and crank pulley. I think the different offset for the belt (transverse vs. longitudinal) is due to different pulleys on the crank and water pump, and a different bracket on the alternator (not in the alternator pulley,) correct?

If don't get confirmation, I can give what I have a whirl, but it would nice to have some assurance that I won't need to pull anything back apart after installing the engine. Thanks in advance!
Jan. 7, 2010 10:00 a.m. Brust Reader

I did the rwd cooling system on my MG- but used the fwd (or MR2) water pump, alt, pulleys etc, with no problems. I used the standard rwd alternator bracket. I think the alternator pulley must be a little longer to use with the rwd water pump/pulley, and crank pulley.
Jan. 7, 2010 10:41 a.m. Dr. Hess SuperDork

The thermostat has a rubber ring that it fits inside of on my 22R's. I bet the 4AG is the same. Without the rubber ring, it will be loose in the housing.
Jan. 7, 2010 8:26 p.m. ae86andkp61 Reader

Cool. I did a further mockup and it does appear that the alternator pulley might need to be a tiny bit longer to line up with the crank and water pump pulley. I think I will use the MR2 alternator as a core and get a rebuilt RWD one.

As for the thermostat, digging into it a bit further, it seems that the AE92 GT-S calls for a different thermostat (also with an o-ring) and all other 4A cars (transverse and longitudinal, 4A-C and 4A-G) call for the same thermostat, just with different gaskets/o-rings and in different housings. I will price out my options, but if I can get an AE86 or an AE82 housing, I can use the thermostat I already have (which is the more common part number) but if I can't, the AE92 thermostat is still available at the moment, so I can get one for the housing I already have, and take my chances on replacements being available if and when I need one down the road.

Thanks, guys! I will be sure to post pics and dyno plot once it is completed.
Jan. 7, 2010 9:06 p.m. Dr. Hess SuperDork

The Corolla AE92 GT-S (4age) thermostat is 90916-03060, subs 90916-03090. That is, they are interchangeable and the 03090 replaces the 03060 part number. It was used in:

87-88 AE82 Rolla FX

88-91 AE92 with 4AGE

87-up AW11

88-89 ST165 3SGTE

9108-9309 Celi 5SFE ST184

91-up 5SFE (and 3SFE) Camry

9806-up 5SFE Solara

9603-up 3SFE Rav 4

So, do you really think there's going to be a hard time getting an AE92 thermostat in the future? If you do, I can supply you, today only, with a lifetime supply of them at only $20 each.

The 4ALC thermostat part number is 90916-03046, which is different than the 4AG's.
Jan. 7, 2010 10:05 p.m. ae86andkp61 Reader

Dr. Hess, I don't doubt your expertise, and your parts interchange list is likely to be more up-to-date or complete. It is a shame that Toyodiy doesn't have both part numbers and line drawings anymore because it makes it harder for me to know what I am looking at, and I don't have an EPC.

It used to be that I never even considered future availability of Toyota parts, but in the past year or two more and more of the AE86-specific stuff is NLA so I may tend to overreact now.

I will call the dealer tomorrow for a thermostat and O-ring...thanks!