I bought a 1995 4Runner (137kmi) with a bad transmission in January. The PO had drained the radiator while it sat in his yard to keep anything from freezing up and I had refilled it with straight water while I tested everything. It took a while to get it on the street but I drove it for 4 days last week and most everything seemed fine. It sat for a couple days while I got correct drive shaft bolts then I took it for a 5 minutes test drive around the block and when I returned I could hear a hissing noise. With the engine shut off I could see steam near the distributor at the front of the engine but no leaks. After it cooled I removed the radiator cap and added about 3/4 gallon which got it near the top. Yesterday I checked on it and topped it off completely. As soon as I added water I could hear it hitting the floor. Looking underneath the leak is dead center of the front of the oil pan. I assume it's running out of something behind the timing cover. I originally suspected the water pump but this leaks when it off AND since it doesn't leak until the radiator is all the way full I'm thinking it's the idler at the top. Now that I know it's leaking for sure, I can see evidence of baked on water/coolant on the bottom of the block. I think the reason I didn't notice it while driving was because the straight water boils/evaporates and doesn't smell (unlike coolant). So, I have no idea how long it has been leaking and I have no idea how hot it got (gauges don't work so well on air).

Next steps:
* run a compression test to see if I can spot evidence of head gasket failure
* pull the front cover to see if I can find the exact source of the leak (with the amount of fluid this should be easy)

My original plan was to make it driveable (for cheap) and sell it to fund my pile of other projects. Every penny I put into it eats at whatever profit I could have made but I'm also a stickler for doing the right thing. Assuming it's the idler, I could do a quick replacement and hope everything else is good. I could replace timing belt, water pump, idlers, cam and crank seals while the entire front of the engine is apart. More money but should last a while. In either case, if the HG is leaking then I've only solved the immediate problem. I also have a complete running 1989 3vz that I got with the transmission I used to fix the truck already. It's basically free except for gaskets and fluids to install it. I just don't have any real, long term experience with it so it may die a day after it's installed. Lastly, I've already swapped my 93 pickup to a 5vz and have a couple vehicles (rusted frames) so if fixing the 3.0 costs more than about $500-600 I'm not even going to bother with it. My biggest problem is time. I really can't spend weeks (of nice weather) chasing and diagnosing known issues on this thing.

Any way, does it seem like I'm on the right track for the cause? Is there anything else I need to be concerned with? What seems like the best approach to move forward?

Thanks,
Troy

 

Hey Troy, I know you said it's near the front? but might be worth it to check the engine coolant temperature sensor, It's almost all the way in the back but would produce that "hitting the floor" symptom when filling the radiator if it wasn't seated correctly/and or out.

 

Definitely front. It's dripping from the center of the oil pan which is about where it's coming out of the cover (it fast enough that it really doesn't change direction on the way to the ground). There was also steam coming out of the timing cover by the distributor the other day when it was hot.

I've been pricing timing belt/water pump kits to just replace it all but my biggest fear is the head gaskets. I don't want to take it apart twice - not to mention the additional expense.

Troy

 

Its probably the water pump. If its been sitting a long time with no coolant then the seals are most likely dried out. It wont usually leak from the pump either until the radiator is full. The thermostat is in the lower hose and will block it off from the engine. Its easy work to pull the upper timing cover to have a look.

 

Thanks for the help so far...

I just checked on it. The coolant level was still just above the fins so it's not leaking down much from the top. All of the leaking I have seen is with the engine off. The water pump is a lot lower than that right? However, it doesn't appear that there is any movement in the radiator while the engine is running. I only ran it a minute so the thermostat definitely wasn't open. The water inlet on that top pulley looks a little crusty from outside. Maybe both went bad? Both come with the timing belt kit so really not much point in buying them all separately.

I haven't had a top cover off a 3.0 in a while (everything else I have is a 5VZ). Don't you have to remove the studs from the water neck to get the cover off? Any idea what socket to use on the studs themselves? The coolant is already drained down and getting that top radiator hose off should be easy. Do I have to remove the fan or anything to get the cover off?

It is stuck at my apartment where I live. My garage with all my tools is 16 miles away. I was thinking that if it were just that top pulley I could replace it easily enough then drive to the garage. Sound like I may need to tow it.

Troy

 

While the studs in the "water neck" can be removed with an external-torx socket, the easy way is to just put both nuts on one of the studs, snub them together to lock them, then unscrew the stud with a 10mm(?) socket.

 

Coolant system pressure test will show your leak on a nice cool engine.

Without the fan and movement blowing coolant all over the place

 

Sounds like a bad water pump. Had the same vehicle. Bought a timing belt/water pump kit on eBay. Fairly straightforward job. Worked fine. Probably a good thing for your engine anyway.

If I recall correctly, there are a number of small hoses behind the engine that can leak.

 

It pours out when I fill the radiator - no need for a pressure test (I just have to remove the timing cover).

Troy

 

Yeah, I ordered the parts. I'm really hoping the head gaskets are ok.

Right now it's stuck at my apartment and all my tools (and space) are at my garage. I don't think I trust it to run more than a few minutes so I'm going to have to tow it.

Troy

 

Just for future edification 'cause you seem to have a handle on where it's leaking already.

​​​​​​​Compression testing is not the right tool. If it leaks bad enough for a compression test to come up low it's going to run like absolute junk and be obvious.

The correct test is a coolant pressure and cylinder leakdown. The first puts coolant on the floor/crankcase(cracked block, bad seals), the second air bubbles in the coolant (gasket, cracking)

 

Ok, thanks. More stuff for me to Google. I felt like it was running low on power before I got home the other night (ie even less power than the standard 3.0). That may have been the ECU freaking out about the heat or just the heat in general. Because it was so low on coolant the gauge didn't show it was hot so I'm not sure what the ECU saw. I may run it around the block tonight to see if it's still sluggish when cold. Parts won't be in until Thursday so I can't really do anything more than pulling the cover and verifying the leak.

I'm not 100% confident in my spare engine. While the cost to throw it in there would be minimal - and I feel it's less labor than doing timing/water pump and head gaskets on this engine - I really don't want something similar happening with it. I'll pop the covers and pan off it today and see if there's anything alarming.

Troy