1992 Corolla 1.6 Auto Coolant Leak - Pre-1997 Toyota Corolla and Geo Prizm

Hi everyone,

I have a 1992 Corolla 1.6 4afe engine with over 208,000 miles. Now the car is leaking coolant and its pooling on the driver side, at the bottom of the engine where the transmission and engine join. It continues to leak even if the car is off. I have checked all hoses and clamps, thermostat, water pump, freeze plugs, and the radiator has no leaks. Was thinking it may be the head gasket, but i drained the oil and removed the valve cover and it checks out ok. No smoke from the tail pipe and the car starts up just fine. Is there something I am overlooking? Cracked block, head gasket issue, hidden freeze plug?

Thanks guys

Check the reservoir tank and overflow hose from the radiator cap - see if it is leaking around there. Waterpump could be weeping as well - though that is on the other side of the engine. Possible that a leak is working from that end to the part where the transaxle bell bolts to the engine.

Given the location, could be leaking at the throttlebody - there are coolant hoses that run through the throttlebody to prevent icing under certain conditions. You also have a small bypass hose that is very close to that area. Many times, these will only leak under pressure through a crack in the hose or even past the hose clamps.

Unlikely to be a headgasket - that shouldn't present a leak exterior to the engine, unless the water jacket is damaged on the outside of the engine.

Ok I will check all of your suggestions post any progress. Thanks

After a week of looking for the cause of the leak still no luck. I got a pressure tester from a local parts store and I am still unable to find the source. Even under pressure there is no visible cause and no hissing sound. It will continue to leak even when its not under pressure. Could there be a freeze plug or something else in between the engine block and transmission that is not visible that could cause such a leak? I can clearly see the leak and at this point its only water which is perfectly clear, no oil or dirt.

Water? Did you mean coolant - either Toyota red or conventional green stuff? If you are leaking clear water - that is likely from your evaporator condensation drain - perfectly normal. Sometimes that drain will get clogged with debris or bacteria - causing it to leak in a weird way.

Freeze plug leaks are pretty uncommon and would be very evident (won't be able to hold pressure, leaks everywhere). Same for leak in the water jacket of the engine block - no coolant lines run through the transaxle, so no issues there. A slow leak around there is possible - given that it seems to be very hard to see, might have to add a tracer dye to the coolant and use a special light wand to see if you can trace the source of the leak.

Happened to me, and there was a funky smell, so I googled. To stop it from happening again use the fresh air setting instead of recirculating for the last 20 miles or so when on the way home where the car sets. I do it once a week all the time now because of this.

Purchased UV dye and light. I am still unable to find the source of the leak so I assume the water jacket is damaged. Now is that repairable and at a reasonable cost or should I give up and call my local salvage yard? Thanks for your help

You mentioned unable to find the source of the leak - did you mean that you were able to see coolant tainted with the dye, just couldn't localize it because it was everywhere? Or did you mean that you didn't see any UV marked coolant anywhere?

If the water jacket is damaged - the block will likely have to be scrapped. Pretty hard to believe that the block is cracked - as any leak there will cause overheating, major loss of coolant. Did you double check the radiator, waterpump, radiator cap, all hoses, fittings, etc.?

Sounds like the system has to be pressure tested to find the leak - you'll have to take it to the shop, as they need to hook it to some equipment to cold/warm pressure test the components. Then let it sit overnight to see if they can reproduce the issues you are seeing.

Not impossible for a freeze plug or block to be leaking coolant - but that is very low probability. I've seen may two cars with bad freeze plugs and zero that spontaneously cracked the block - outside of not using antifreeze (cracked the block in subzero weather + running straight water), overheated the engine, run without coolant, accident, or other catastrophic occurrence like throwing a rod, etc.

I was able to see the leak with the dye and UV light. The car was in a pitch black garage and I used the cooling system pressure tester I previously rented. I was just not able to see a bright glow at the source of the leak just where it pools at the bottom of the engine and tranny. The freeze plugs are good as well as the rad, hoses, water pump, thermostat, heater and bypass hoses. I'm stumped

Well I found a '91 Corolla DX in very good condition for a low price, so off to the scrap yard for old blue. thanks for the help.