2000 Toyota Solara 3.0 V6 massive coolant leak

Hi guys,

Its Pop again, and first off I would like to thank you guys for all the help you have been to me over the years. I always try to post back with results and my sincere, heartfelt thanks, but if I have forgotten to do so on any of my threads let me here say THANK YOU to all you guys who make this IMO the best repair forum o the internet.

So here is the latest: My daughter's Solara has a pretty big coolant leak. She says she was driving and heard a "POP" and then saw steam coming up from the hood. She stopped immediately. She said the temp gauge stayed in the middle of the range and did not get anywhere near the red hi-temp zone.

When I pour water into the pressure cap opening, the water gushes out just as fast as I can pour it in and cascades down the back of the engine, from very near the top of the engine, primarily on the drivers side. . My guess is the rubber bypass hose that goes from the opening under the pressure cap over to the back of the thermostat housing has completely let go; as I cannot see any other leaks from anywhere else.

The problem is how to verify it visually. It looks like the hose runs under the lower intake manifold. I've tried to look using my borescope, but can't really see any part of the bypass hose. It looks like I am going to have to remove the intake and related top-engine stuff just to get a look at it.

Any ideas?

Thanks, Pop

A hole like that shouldn’t be hard to spot. There’s hoses for the throttle body and EGR cooler back there. Start with the air cleaner and throttle body and see if you can spot it. An inspection mirror would be helpful too

Hi popoften,

I think you should also look for the root cause of broken hose.

Is it due to a bad water pump? Is it due to a plugged thermostat?

Good idea on the mirror. I'll get one. Thanks!

Yes this is important. I did replace the thermostat even thought the old one tested good. I thought that was the leak but it turned out that was not the only leak. Water pump is circulating the coolant. I am growing increasingly concerned there might be exhaust gases leaking into the cooling system that created the pressure. But with a leak this big, I doubt a chemical test of the cooling system will be very revealing. I could be wrong about that. I guess I could try a leak-down test.

New thermostat, and the coolant still dumps out? :huh: Sure sounds like it's coming from the engine valley and running down the back of the bellhousing.

The best idea I have is a leak in the hose between the water outlet and the thermostat housing. Parts diagram for reference, part #21:



I've seen the water outlet gaskets seep, but never gush the way you're describing. The mirror may be your best bet - or a cheap borescope! Never seen that hose fail, but there's a first time for everything. :silly:

Well I finally had a chance to get back to this project and the hose underneath the lower intake manifold was indeed ruptured see picture below. I’ve got another question while I have this engine opened up:

Before I started working on this thing The check engine light was on and I pulled the codes using my somewhat rudimentary INNOVA (displays SOME freeze frame data for some, not all codes) code scanner.

PCM had stored a P0325 and P0330 code having to do with the knock sensors. There was no freeze frame data for these codes. I figure while I have the top of the engine torn off it might be a good time to check those sensors. I did not feel any misfires back when the car was running.

Visual inspection reveals that one of the sensors seems to be damaged and if I had to guess it looks like they’ve been replaced before but I’m not at all sure about that. Are there tests that I can do on these knock sensors with the engine partially disassembled/not running as it is ?

Thanks, Pop

You can hit it gently with a screw driver and see the noise produced. But you need a scope to do so.

About the hose. That kind of ruptured (longitudinal) is due to over pressure. I does not seem fatigue, neither aging.

I'm afraid you have not found root cause yet.

Yes, as I said earlier, I am thinking I might be dealing with a head gasket leak. Can I get valid leak down test results with the intake manifolds off?

Yes you can.

I'd say is the same results, since you are testing inside chambers, which are connected with intake manifold through the valves (which are closed when you perform the test).

Of course, you can only test that way, engine cold condition

Thank you. So, if I understand correctly, I can do a leak down test with both upper and lower intake manifolds removed. I guess I will listen for air at the coolant passages that connect to lower intake. As for the knock sensors, I’ll have a buddy bring a scope over.

Correct. You can do it without any manifold (again, checking only engine at cold).

You can also have a leak that only "appears" when engine is hot (which you can not detect, because you are not able to warm up the engine).

On the other hand, i don't think you can hear the air at the coolant passages (unless you have a huge leak)

I suggest you to fill coolant passages with coolant and observe for air bubbles.

Scope testing the knock sensors is a great suggestion. If that doesn't work, you can also do some quick resistance testing. Maybe someone with access to SI can help out. But, TBH, these knock sensors go bad so often that I'd consider replacing them regardless of your testing results. If you don't, and the codes come back again later, you'll have to take all this junk back off again.

BUT, that all depends on your leak down results. :silly: You can definitely do a leak down test with the intake off, like guafa said. Filling the cooling system and looking for bubbles would be best. If that's not an option, you can leave the tester installed for a minute or two at full pressure and remove the radiator cap. If you get a pop of pressure, game over.

Alternately, if you have a cooling system pressure tester, you can have it installed on the radiator while leak down testing. Building pressure is a failure.

Well, after some illnesses in the family, I finally have some time to get back to this car. Last week I did leak-down tests of the rear three cylinders, and there were no bubbles coming up the coolant passages at all. Not even tiny ones. I am going to do the front three cylinders today. I'm going to have to use a borescope to see the coolant on the front cylinders because the front cylinders are canted higher than the rear ones so the coolant level strays too low in these higher coolant passes to see directly.

Well I think I finally have an answer. In trying to get a definitive answer as to whether I have a head gasket leak I checked the front three cylinders with my leak-down tester and I can hear air coming out the middle intake runner when I pressurize the middle cylinder. I repeated the test on that cylinder about six times. I am pretty sure I had the piston at TDC on the compression stroke, and there is no doubt I can see and hear air coming out the intake runner. I have not seen any bubbles in the coolant passages though. Maybe that doesn't happen unless the engine is actually running.

I guess I am wondering at this point if I dare attempt the job. According to the Haynes Guide it looks nasty. Apparently you have to dig into the timing system as well. Or maybe the thing to do is look around for a decent used engine and bolt that in.

What do you guys think?

~ Pop

Unfortunately, leak down testing for head gaskets is kinda like the ohm meter. If it fails, it fails. If it passes, it may or may not be good. While the #4 cylinder (front bank, middle cylinder) was leaking, what was the reading on your leak down tester?

A leaking intake valve is definitely a problem, but doesn't account for your blown hose. :huh: Plus, I've never seen a valve leak on one of these 3.0L engines. They have their problems, sure, but leaking valves isn't one of them.

When you say you repeated the test about six times, did you also roll the engine over after every attempt? Because I've been burned by leak down testing before, when a bit of carbon finds its way onto a valve while hand cranking an engine (for whatever reason). Spin it over a few times, and the leak disappeared.

If you didn't get any bubbles in the cooling system, then I'd say reassemble and run a chemical test. If that passes, let it ride.

If you decide to do head gaskets, it's not terrible. The timing belt is one of the easiest out there - the belts themselves are pre-marked so you can't get it wrong. :silly: The rough part will be the exhaust manifold nuts. They love to seize/round/break studs off.

Yes I rotated the engine back around to TDC each time I repeated the test. I did not get consistent readings on my leak down tester because I blew the gauge by running too much pressure through it.

I think I will just put the motor back together and run the chemical tests as you say. It is pretty clear I cant replicate the intrusion of exhaust gases into the cooling system with this approach.

I REALLY appreciate your guidance Tyler! ANd that holds true for all you guys. You are the best.