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My LS400 is losing coolant slowly. On longer highway drives, there is smoke/steam coming out from the driver's side firewall area.
I tried looking from above to see if I can see the leak, but it didn't work. I then tried jacking the car up and looking from below, but again, I was unable to find a cracked or rotted hose.
From what I understand, the previous owner bypassed the heater control valve or something-- I don't exactly remember what he said.
Can anyone help me pinpoint what the problem might be? For example, what is on the driver's side firewall area that could be leaking? Any common issues that I should be looking for? Should I buy a pressure kit and UV dye? If I take it to a shop for a leak, how much can I expect to pay?
Before anyone can help we'll need to know the year of the car and the details regarding the heater valve potentially bypassed ?!?!?
A pic of your heater valve would be helpful.
Most coolant leaks can be diagnosed pretty easily by using one of those pressure testers you can rent for free from PepBoys, etc.
You'll probably need some special adapter vs. the regular one. Sometimes that comes in the kit. Sometimes you need to rent a second tool which is the adapter alone.
It fits on the cap on top of the coolant reservoir.
With the engine cool and dry, you can pump up the pressure and be as careful as you want, looking for small leaks.
I just tried the pressure tester. It held pressure (12 PSI) for about 30 minutes. No leaks; floor is completely dry. No hissing sounds or squirts of coolant anywhere as far as I can tell.
Should I warm up the car with the pressure tester on? As far as I can tell, the car only leaks after long trips on the highway. That's when smoke starts coming out from under the hood.
Given that the last thing that someone messed with on this car had to do with the heater, could it be a loose heater core hose? Is there a diagram of all the radiator hoses that I could use? I was thinking of just replacing all the easily accessible hoses toward the back of the engine, but I would need a diagram to know which hoses are radiator hoses.
Slight changes were made to the heater hoses close to the firewall in 94. Do you need before or after that ?
After, please. I have a 98.
I ran the engine for a few minutes and looked for leaks again. Again, I couldn't exactly see where the white smoke is coming from, but it is definitely coming from somewhere below the left cylinder bank (driver's side cylinder bank).
Would this indicate a blown head gasket instead of a simple external coolant leak? Car is otherwise running completely normally. I checked the oil, and it's not milky at all. There's also nothing coming out the exhaust.
Sounds like you have already done a pretty thorough inspection and a diagram wont be much help but here it is anyway.
Might be time run to the local parts store and grab one of these...?
Last edited by bradland; May 7, 2018 at 12:56 PM.
Reason: typo
I ran the engine for a few minutes and looked for leaks again. Again, I couldn't exactly see where the white smoke is coming from, but it is definitely coming from somewhere below the left cylinder bank (driver's side cylinder bank).
Would this indicate a blown head gasket instead of a simple external coolant leak? Car is otherwise running completely normally. I checked the oil, and it's not milky at all. There's also nothing coming out the exhaust.
Looks like the leak is evaporating due to engine heat. What pressure level (in PSI) did you use for pressure testing? No white exhaust from tail pipe? You can taste the soot to see if it taste sweet indicating heat gasket issue. Can also use dye to track the trace of leak under the hood.
Hey, also, this is pretty obvious, but ... the one thing you take off the system to do the pressure test is the radiator cap. If that is the part that is leaking, well your pressure test will still be tight. Could the cap be leaking, or opening at too low a pressure? It is supposed to open at a preset pressure (that is not supposed to be reached unless something goes wrong) at which point, it allows pressure (gas, liquid) to escape via the drain hose.
post pictures of the bypassed heater control valve. It's on the firewall, dead center, top. With a nonstandard config it's impossible to guess what could be leaking. My guess is whatever he used to do the bypass.
Hey, also, this is pretty obvious, but ... the one thing you take off the system to do the pressure test is the radiator cap. If that is the part that is leaking, well your pressure test will still be tight. Could the cap be leaking, or opening at too low a pressure? It is supposed to open at a preset pressure (that is not supposed to be reached unless something goes wrong) at which point, it allows pressure (gas, liquid) to escape via the drain hose.
I didn't pressure test the cap. I'm not sure if my kit can test the cap, but I'll check. If anything I'll try a cap from another Toyota vehicle that I have, because none of my other vehicles are losing a drop of coolant.
Where is the drain hose? Could it be by the firewall?
Here is a pic of the coolant tank that I just pulled off eBay.
The cap is spring loaded to keep a tight seal, and then to release when a certain blow-off pressure is reached. If nothing goes wrong, it should never release, but if there is a problem, it will release pressure rather than having stuff explode. The blow-off goes through that little tube where the cap connects, connected to a hose, and generally running down so it spills out on the ground without causing any mess. Pretty much all cars are like this one way or another.
Last edited by oldskewel; May 11, 2018 at 12:24 PM.
Well I added the UV dye and I drove the car for a few miles. I stopped after I could clearly smell something coming from the engine compartment.
I noticed that after I filled up the reservoir with RED, Toyota antifreeze, the car stopped smoking as much as before. There is almost no signs of smoke now, even when pushing the car hard. Before, when the car was low on GREEN, conventional antifreeze, there would be significant amounts of white smoke coming out from under the hood. Basically, right now I have a mix of Red and Green coolant in the system because the system was low before, and I had nothing but Red on hand, and I figured that mixing the two shouldn't be a giant issue. I've done it before with no ill effects other than creating a coolant that looks kinda weird in color.
Is the UV dye supposed to color the smoke as well that comes out?
I got under the car and shined the UV light around and I saw nothing but small oil leaks.
Need help finding coolant leak
