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Discussion Starter #1
I'm pretty sure its time for a new one. As well as the timing belt while im in there. I also intend to replace the tensioner and the seals, new housing aswell. The whole nine.

So as for some time, I've had an somewhat mysterious coolant loss problem. Been going on with it and just topping up coolant as required. Keeping a close eye on it.

Recently I noticed my radiator cap is wet on top, in a big circle, and is quite jiggly on its underside and all the mechanical bits of it are quite clearly worn and no longer adhering together as they should. So it needed to be replaced, for sure. Upon replacement of this part, I hoped that the coolant loss would now slow down, assuming that it was able to steam out of the cap over lengthy (1/1.5 hrs) drives. Well, I installed the new cap, and noticed that my coolant was now just "leaking" quicker. Mind you, when I say leaking, I mean a detectable stream. For a long time its been just vanishing, never known where its been going. It wasnt until I replaced the radiator cap that it actually began visibly leaking to any degree - After about 2-3 days of driving and keeping it topped up, whilst on the way today to the parts store to purchase who would've guessed - more coolant - I noticed on my way out a small puddle had formed under my car. I've always considered myself one keen to check for leaks, as I do on a fairly routine basis to ensure my gas tank is still on the straight and narrow - quick tip, if you have a gas tank that leaks, and worse if its more full, leave your gas cap loose and see if it helps you out. Anyway.

So the leak is coming from the water pump area, its nice and wet directly under the water pump - and its making its way down to the oilpan, then dripping off the opposite edge of the oilpan, closer to the radiator. If the car is running, youre looking at a safe 4-10 drops of coolant a second raining out. It slowly eventually creeps to a halt after the car has been shut off.

Needless to say, I have deemed it now out of commision and will not be driving it until I have corrected the issue. I am very curious as to why this visible leak didn't exist before I replaced the radiator cap. My guess is the cap was the easiest place for pressure to release, so once I took that away and pressurized the system accordingly, it just decided to head to the next weakest point and wreak havoc. If anybody wants to educate me on the reasons for this happening as it has I'm all ears, very curious.

I'll be posting a video to demonstrate as soon as I can. Thank you all for your feedback!
 

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1994 Corolla DX
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Have you ruled out the short piece of hose directly behind the water pump? Very common leak spot.

Not advocating against replacing the water pump (if you do, get an OE Toyota or AISIN) but as a stop-gap solution if you need it back on the road quickly that hose is faster to replace than the whole nine yards of water pump replacement.
 

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The radiator cap is what actually gives the cooling system pressure, so a brand new cap almost always restores pressure to a system with an old/original cap.
It's likely the seal on the old cap might have been leaking and/or the cap was just old so it wasn't pressurizing the system all that much if at all, and when you put the new cap on, the newly sealed system and additional system pressure caused the water pump leak to be the sole spot for it to leak from, and of course the higher system pressure caused the leak to be worse.

Water pumps have a weep hole near the bottom, and they actually leak by design when they are starting to wear out. The leak could be a failing o-ring/gasket, but if you see buildup/deposits around the weep hole or just a direct stream of coolant from the weep hole down the pump and engine, you know it's time for a new pump.

I'd suggest a new AISIN (same as OE Toyota, but less expensive) pump.

Great time to do the timing belt, tensioner, etc. as you mentioned.
 

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Discussion Starter #4
Funny you should mention it RollaDad, a good couple years ago the hose youre speaking of did happen to almost catastrophically fail on me. It had ballooned up something fierce, and was, not unlike my water pump, dripping coolant at a steady rate. Upon removal I noticed that it actually had split on the underside (ofcourse, the side you cant see without removing it) just enough to allow coolant to seep through. I'm amazed to this day that it never just busted wide open and dumped all my coolant out. I replaced it with a very stout piece of rubber hose from NAPA, with steel braiding on the inside and also nylon wrapped, so its not going anywhere ANY time soon. Put new clamps on it aswell. Thanks for mentioning tho.

Also I noticed that both of you so far keep mentioning AISIN for the brand to go with. Why is this? Is there anything wrong with DAYCO, or atleast in comparison? Thanks guys!
 

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Make sure you figure out where the leak (or leaks) are coming from before you do the timing belt or you might just be wasting your time if the problem is a head gasket. It sounds like the bypass hose, but could be several sources and it could save a lot of frustration to make sure you have determined the leak sources FIRST.
 

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Discussion Starter #6 (Edited)
I do definitely intend to do some studying on it under the hood and pinpoint precisely where its coming from. I'll be freakin amazed if its the hose, and I really don't think thats what it is, but I will certainly inspect it and assure that it's in good shape, and that the clamps are still holding it on there tightly.

I'll also need to remember to bleed it, at some point throughout this whole thing, ofcourse.

I should say I'm skeptical of it being a head gasket issue. If it is, wouldn't this have shown itself in some shape or form before I effectively re-pressurized the system? Beforehand it was escaping through the cap, and much slower. Now that its pressurized well, it's pretty hard to miss the loss of coolant or the puddles. Why would it make any sense for it to be a head gasket if it wasn't visibly leaking beforehand? Surely it would've shown visible signs of leakage even before it was pressurized, correct? Get this: A couple of years back at the time of replacing my rear hose, many users on here we're also speculating that it could be a head gasket issue causing the coolant loss. It was the rear hose. I replaced the hose, and didn't need to top up my coolant for many months, nigh on a year or more before I had to slowly start adding it again. It began getting worse, and the radiator cap started getting wet looking on top, so I decided to replace it and here we are. Point being, I'd be really impressed if it was a head gasket failure that is causing the actual VISIBLE coolant leak.

Also I'm pretty sure there would be other symptoms associated with this sortof headgasket failure, would there not? Would it just be leaking some coolant, and thats it? No rough running or smoking or rough idle or etc? If so, atleast if nothing else I could save money for quite some time just buying coolant instead of a head gasket expense.

Really quick as well, I need to replace my coolant temp sensor. Not sure which one to buy. I'm looking on rockauto and they have different lengths, different threaded lengths, different adapter style ends, the lot. Figuring the ULTRA-POWER 5S1517 is the one I need. And what does "with gauge" mean on those? Does removing the current sensor mean a bunch of coolant will start pouring out while im trying to install the new one? Thanks yall!
 

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Which sensor is broken. The one for the temperature gauge on the cluster? And are you sure that's the problem?
 

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Discussion Starter #9
Which sensor is broken. The one for the temperature gauge on the cluster? And are you sure that's the problem?
Yes and yes. My temp gauge has misbehaved for quite some time. I'm attempting to fix it by throwing $3 at it lol. Just not sure which one to buy - ofcourse unrelated to the issue I started this thread over
 

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1994 Corolla DX
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Also I noticed that both of you so far keep mentioning AISIN for the brand to go with. Why is this? Is there anything wrong with DAYCO, or atleast in comparison? Thanks guys!
If you search the forum you can find multiple examples of aftermarket water pumps that failed prematurely. Very commonly the impeller simply rusted off and dislodged. Being one of the most critical parts of the engine I don't see the need to "make a bet" on an unknown entity when OE Toyota / AISIN (OE manufacturer) is a known entity and known to work flawlessly.
 

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Discussion Starter #11 (Edited)
So I've been researching for the task, reading about all over the place, also I have determined the leak is indeed at the water pump, and is coming out of the weep hole.

Checking out some threads on timing adjustment and etc, stumbled across 94RollaDads' tutorial on adjustment at the distributor. I'm just curious about this:



So thats the sticker that goes on OBD-I corolla hoods only, correct? Given mine was manufactured in 2/95, I figure mine MUST be obd1. Has a diagnostics port under the hood, I've checked for codes on it by jumping terminals, all that business. Yet this sticker isnt what I have on my hood. THIS one is:



Replaced hood maybe? Not the factory original I'd say. Anyone else had this oddity? And incase anyones wondering, yes I'm pretty confident the distributor is adjustable. Havent tried, but I'll find out here soon...very curious. Lol Thanks guys

**EDIT** should clarify, that sticker is precisely the one I have on my hood save for the fact it says 7A-FE at the bottom, not 4A-FE and its a 1.8L, not a 1.6. According to the sticker anyhow
 

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Pretty sure the VIN has a code for the engine. That coupled with your model year should get you the info you need to do a proper scan.
 

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Discussion Starter #13 (Edited)
How could I determine beyond the shadow of a doubt exactly which engine it is? I've always been firmly under the impression that it's got a 1.8L, given that its a DX, but now I'm just getting confused because upon running the vin it tells me its a 1.6L...yet with DX trim?? Did they make DX trims with 1.6's? AC, power locks and windows, etc? I don't think they did.

Mind you I'm using some free VIN website for that first result. So I went to https://parts.olathetoyota.com/vin-decoder which is also free to check again. THIS tells me its a 1.8L, again, DX.
 

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1994 Corolla DX
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The 4A-FE has a single oil pan. The 7A-FE has a double-decker oil pan.

Also, the engine is marked in the cast iron below the upper coolant hose from the radiator. You may have to get a flashlight and a rag and get some gunk off to read it.
 

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The 7A-FE 1.8 is identifiable by its oil pan. I believe it's a big cast iron deal or something, whereas the 4A-FE 1.6 has a stamped-steel oil pan. What does the engine tag on your firewall say? It should be down at the lower center of the driver's side of the car - assuming LHD.

Maybe you could delete the 1.8 for a credit, when buying a DX. I've never seen a 7th gen without AC. My base model is a 1.6 and has AC, and I suspect that you could've ordered all of the nice DX power features as ala-carte options on a base model, and still gotten the 1.6, so I don't think that it's impossible that your car came with the smaller engine.

Those one-VIN-reader-does-all sites can be sketchy because of all of the makes and models they would need to gather correct info for. If you can find a Toyota-only VIN decoder online, I'd be more inclined to trust that.
 

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Discussion Starter #16
A small detail I've also noticed in 1.6L vs 1.8L variety corollas of this generation - the gauge clusters. DX trim gets 4 gauges, speed, gas, temp, and rpm. any lower trim only gets 3. Also, 1.6L usually "redline" - hit the red zone on the gauge - at about 6200 RPM, whilst 1.8L hit it at about 5800 RPM. Mine hits at 5800. The toyota site tells me its a 1.8L
 

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A small detail I've also noticed in 1.6L vs 1.8L variety corollas of this generation - the gauge clusters. DX trim gets 4 gauges, speed, gas, temp, and rpm. any lower trim only gets 3. Also, 1.6L usually "redline" - hit the red zone on the gauge - at about 6200 RPM, whilst 1.8L hit it at about 5800 RPM. Mine hits at 5800. The toyota site tells me its a 1.8L
DX did not necessarily get tachometers. I am not sure what the specifics were, but manual drive DXes seem to have them more frequently. My DX (automatic) did not have it, and many other DXes did also not come with tachometers.
 

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Discussion Starter #18 (Edited)
That makes sense, however I'd be inclined to believe that if only certain DX's got more than the 3 base tachs, then for sure no base models were ever equipped with more than 3, correct?

Also on the sticker in the door that explains where it was made and etc states its a AE102L. AE102 = DX, with 1.8L 7A-FE. AE101 = Base, with 1.6L 4A-FE. Would be curious to find out what the L means in AE102L, but anyhoo. Found the VIN on the block too under the top rad hose, stamped tallways, matches the VIN so I know its the engine it came with and all that. Was never my concern that, but did definitely want to assure its a DX so I'm glad to have all this figured out, thanks yall for the clarification!

add: Yes I have 4 gauges. RPM is the additional gauge that you get if you have a DX. Base models/everything else gets gas, temp, and mph.
 

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1998 AE102, 2018 ZRE182
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The 7A-FE 1.8 is identifiable by its oil pan. I believe it's a big cast iron deal or something, whereas the 4A-FE 1.6 has a stamped-steel oil pan
7A is two-piece - upper section is cast (I believe alloy), lower section is pressed like a normal one




Would be curious to find out what the L means in AE102L, but anyhoo.
L=Left Hand Drive
 

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Discussion Starter #20
Ah yes, brilliant! Thank you much. Just got those sitting around? I'm impressed lol - I'm curious why they made the 7afe's a 2-piece?
 
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