Just had to leave work early today to rescue my wife and kids who were stuck on the side of the road with an overheating engine. So thankful she knows to stop driving when the temp goes into the red. My ex never seemed to get that concept. Anyway, it had cooled down by the time I got there and sure enough the little tank was empty. It had overheated from a cold start in about 10 minutes of driving. I didn't see any obvious leaks and had no coolant with me so I thought I'd just start driving it back home (on country back roads where we can pull over most anywhere) and see what happened. I ran the heater full blast but as I watch the temp climb I never felt any heat coming out. That only confirmed that it was quite low on coolant. Before it could overheat again I came to the little one lane bridge on our road and stopped there for some creek water. After that it registered normal temps, heater was blowing hot air and drove normally the rest of the way home. Once home I popped the hood and looked around for leaks and saw the tank was damp. Before I popped the cap I checked the upper radiator hose to see if it was still pressurized. It wasn't which I thought was odd having just driven it for several minutes. So I took the cap off and as I did so something fell out from inside the cap. Turning it over I realized that the valve in the cap was broken. That'll do it. The cap couldn't keep the system pressurized and so the coolant was able to boil off until the level was low enough to cause overheating.
Why didn't the low coolant light come on before? Well actually it did. It's been on for some time but every time I checked it the level was just fine. I figured it was a gunked up sensor so we started ignoring it while we worked on higher priority problems, planning on fixing it later.
Yeah.
A replacement cap was had for only $6.99 and it's good to go again.
Sometimes I wonder why I don't pay more attention to those little lights.

 

OK, so I put the new cap on and everything seemed fine that day. The next day it started getting overly warm. Not exactly overheating but running warmer than normal. I checked and the tank was empty again! Again I looked all over and under this engine and could find no leaks, no wet spots, no puddles underneath, nothing. Yet somehow it's low on coolant again. Maybe I didn't refill it all the way before. I added more coolant and it ran fine the next trip. Before I went out the next time I checked the tank first and it was low again. Again I looked all around and underneath and could find no visible cause for the coolant to be low. This has been going on now for days with no change. Each time I get ready to take the car somewhere I pop the hood and check the tank. It's low and I add more. Cap it and tighten the cap according to the directions printed on the cap. I look all around the engine, the radiator, underneath, at every hose connection and along each hose. No leaks, no signs of there ever being a leak. I drive it and at the end of the drive I pop the hood and check everything again except I don't pop the cap off the tank since I can feel pressure in the upper radiator hose. I see no leaks but smell hot coolant.
I'm hoping that it was just that low on coolant and it's taking a while to bring it back up to level since I'm only able to add a little at a time through the plastic tank. I'm hoping that the hot coolant smell if from spilling it one time. It doesn't overheat anymore but I do smell that hot coolant smell each time I get out of the car. I've checked for steam coming out of the tail pipe and have not seen any. The engine still runs just fine.

Anyone have any suggestions?

 

Check the filler neck and make sure it's not cracked or maybe has a piece broken off. I had that happen on a Geo Prizm I once had and it just about drove me nuts until I found it.

 

1)check the oil. Is it like a milkshake instead of the way normal oil looks? You likely have a blown head gasket.
1a) Does the exhaust have a sweet smell to it?
2) Check where the plastic end tanks of the radiator meet the metal portions. These seals eventually fail but you cannot detect the leak under normal circumstances because the wind blows away the leaked coolant.
You can only really find this one by letting it idle in the driveway and looking, looking, looking.....

3) Check the plastic end tanks of the radiator near the radiator mounts (4). These are very common failure points for s car radiators

4) While the engine is cool, unattach the coolant reservoir tank from the side frame (leave everything else attached), fill the reservoir to full, and idle in driveway. Keep an eye on the side of the tank that was up against the frame and the bottom of the tank for leaks.

5) check the interior of the car for wetness on the pass side floor. In theory your heater core may have a leak in it. Do you smell the hot coolant smell within the vehicle?

6) Try to trace the source of the hot coolant smell as the car warms up from a cold start

Any white smoke out the tailpipe?

 

Rube- filler neck is fine

Derf- oil is good, exhaust is normal, interior is dry and there's no smell inside the car, no white smoke out the tailpipe.
I'm taking the day off Saturday to go over this thing again. I'll be checking the radiator, tank and H2O pump both cold and as it warms up.

I appreciate the tips everybody!

 

my chips are on plastic end cap seals

 

Was able to watch this thing today as it warmed up. Couldn't see anything leaking and again no visible signs of leakage. System built up pressure normally and still no leaks. I found myself leaning over the drivers side with my face over the rear of the engine looking for leaks around the heater core connections and noticed a smell of hot coolant. Still no visible leaks and I'm tracing every hose and seam I can find. For kicks I grabbed the throttle linkage and gave her a couple revs. Immediately I saw steam and smelled strong coolant smell. It was coming from under the air intake pipe so I looked underneath it and gave it some more revs. Sure enough out comes a fine spray of hot coolant from that little extension of the intake manifold that the little hose from the top of the tank connects to. What coolant was dripping was landing on the hot exhaust. No wonder I couldn't find any sign of a leak before. It only leaks when I rev it with the system pressurized and the exhaust dries up the drips. There's a hairline crack on the side of the little pipe like extension that's part of the plastic intake manifold. It seems to follow the mold seam so I guess this area was cast too thin. Now why did they have to make that a part of the intake? I'm going to have to replace the entire intake to fix that.
Anyone know of any problems I might run into replacing this intake that are common to this engine? Anything I ought to do while I have it off the car?
I'll have to wait a week or two before I can take it off the road long enough to do this (not to mention I need cash for parts first, and find a good intake too). This is still my daily driver and it still has the funky transmission with no reverse or 2nd gear. Interesting times indeed.

 

To the best of my knowledge, 99-2001 Intake manifolds (DOHC) interchange (please double check this). So that should give you a good range to hunt down from any 99-2001 SL2, SC2, or SW2 in the junkyards or on ebay.
_________
Can you live with no 2nd gear and reverse slam? 2nd and reverse both share the same solenoid in the valve body. Pulling the valve body and measuring resistance across each solenoid, followed by the swapping positions of that one with another solenoid should tell you if it is a solenoid issue, or a larger problem than that.

NOW is the time to do the above diag step. If it is the solenoid you can get rebuilt ones on ebay--actually never checked for individ ones; people like to rebuild the whole valve body and sell as a unit. Probably best to just get an entire rebuilt valve body so that theoretically you should not have to deal w this again. If reverse slam persists, check he input shaft nut.

Will be easier with a bunch of stuff out of your way, though it is below the ABS unit and apparently if your hands are small enough you don't need to move the brake stuff out of the way. Rube has done the valve body R & R and should be able to give you some pointers.
________________

You'll be removing the fuel rail, injectors, and throttle body.

Throttle Body

Great time to clean the throttle body (use throttle body cleaner, NOT carb/choke cleaner). Since it will be off the car, you can do a more though cleaning.
No idea what will happen to the throttle body gasket upon throttle body removal. I'd be prepared replace the gasket personally, so have one on hand.

Injectors

An opportunity to replace the likely original o rings Run a mess of injector cleaner through the system to (supposedly) remove deposits within the injectors

Fuel Rail

Run some fuel system treatment through. If there are any deposits they (theoretically) should be cleaned out

Going brain dead. More later......