Need ideas on where to look for a slow coolant leak

[WiscoProud]

I have about 193k on my 2004 LC and am experiencing a slow leak. I checked my over flow the other day and saw it was dry. I then noticed i couldn't see the coolant level in the radiator. I topped it off and everything seems fine, but i'm obviously losing it somewhere.

I previously replaced the heater Ts and the coolant hoses, and neither are showing any obvious leaks. I don't notice any puddles of coolant under the truck either, and theres no white smoke at start up.

Any ideas on where to look? The leak is so slow that its not a big deal to just check it on occasion and top it off, but if there's something actually wrong I would like to fix it.

Thoughts?

 

[flintknapper]

If your overflow reservoir was dry and your radiator below line of sight then either its not a 'slow' leak or you don't inspect the fluid level very often.

I understand that you mean its not a 'gusher' (obvious signs on the ground or steam under the hood).

Look for areas where a leak could occur and the coolant evaporate or otherwise be trapped.

Rear bypass if leaking would leak on top of the engine. Water pumps tend to leak only when running (check the weep hole below/behind the crank pulley). Pin holes in any coolant hoses will sometimes leak slowly when the vehicle is running but not when it has cooled and the engine is off.

Rear heater lines/hoses. Heater core (check for wet carpet or steaming of windshield).

 

[WiscoProud]

I admittedly do not check the coolant very often. That will be changing however. I haven't see any pooling or anything obvious on top of the engine, but I'll take a closer look this weekend.

I did have an issue with wet carpet a month ago or so, but I chalked it up to a bad windshield install and torrential rain. It didn't smell like coolant either.

Every now and then I can get a whiff of coolant from the engine bay, but its never strong enough to localize.

 

[flintknapper]

I admittedly do not check the coolant very often. That will be changing however. I haven't see any pooling or anything obvious on top of the engine, but I'll take a closer look this weekend.

I did have an issue with wet carpet a month ago or so, but I chalked it up to a bad windshield install and torrential rain. It didn't smell like coolant either.

Every now and then I can get a whiff of coolant from the engine bay, but its never strong enough to localize.

IF you have Toyota Red or (Zerek Asian) coolant they will both dry up and crystallize when they contact any hot surface. So look for a pink crusty buildup anywhere. If you are running a green coolant it should be easy to spot.

 

[AllLC]

How old is your radiator? The 99 might be different than yours but the top of the radiator housing can sometimes steam just a little bit under pressure. might not be bad yet, but if that's it i would def replace asap. I found rock auto had great prices and they actually had them in stock. I hope you find your leak.

 

[flintknapper]

How old is your radiator? The 99 might be different than yours but the top of the radiator housing can sometimes steam just a little bit under pressure. might not be bad yet, but if that's it i would def replace asap. I found rock auto had great prices and they actually had them in stock. I hope you find your leak.

^^^^^ Good suggestion. That is what happened to my 99. Could not find an obvious leak for some time. Finally noticed a small streak from the upper corner that was leaking down the side of the radiator. The seam at the top had begun to separate (leak).

 

[WiscoProud]

How old is your radiator? The 99 might be different than yours but the top of the radiator housing can sometimes steam just a little bit under pressure. might not be bad yet, but if that's it i would def replace asap. I found rock auto had great prices and they actually had them in stock. I hope you find your leak.

As far as I know its original. I haven't noticed any steam, but if there is some that would account for the mild coolant smell i get sometimes. I've read before about minute cracks in the radiator leaking.

I'm using Green coolant. Shop put it in when I had to have my hoses replaced.

 

[bucfl]

At what level should the coolant be in the radiator from the cap? I may need to replace my cap as i have filled to rim and i get a little build up on lower corner of radiator on driver side. After a while i get no more leak. I dont see any leaks around cap area.

 

[bucfl]

As far as I know its original. I haven't noticed any steam, but if there is some that would account for the mild coolant smell i get sometimes. I've read before about minute cracks in the radiator leaking.

I'm using Green coolant. Shop put it in when I had to have my hoses replaced.

Color doesn't matter as long as the composition meets Toyota recommendations. My wife's Honda is blue... lol

 

[re_guderian]

Radiator leaked on my 2000.

 

[AllLC]

i only run Toyota pink and it took forever to flush the coolant from the po. I don't think this has anything to do with your leak but when i replaced my water-pump i read a lot of horror stories about some types of coolant having a reaction with some internal components. The toyota pink is expensive but if i only have to flush once every (dont know what frequency fsm calls for) its really not alot of money for piece of mind.

 

[ptrsn]

I have about 193k on my 2004 LC and am experiencing a slow leak. I checked my over flow the other day and saw it was dry. I then noticed i couldn't see the coolant level in the radiator. I topped it off and everything seems fine, but i'm obviously losing it somewhere.

I previously replaced the heater Ts and the coolant hoses, and neither are showing any obvious leaks. I don't notice any puddles of coolant under the truck either, and theres no white smoke at start up.

Any ideas on where to look? The leak is so slow that its not a big deal to just check it on occasion and top it off, but if there's something actually wrong I would like to fix it.

Thoughts?

 

[bucfl]

I think you rent a radiator pressure test kit and other tools from Advance Auto.

 

[atnolan94]

You can shine a light down to your rear bypass, you will see it leaking with engine running if that is it. Here is a picture from when I replaced mine. You can see that vertical metal tube that is pressed into that cast piece. It will leak right at that press fitting. These often get damaged when the T’s get replaced because people are a little rough with them. I don’t think this is it, it’s usually a significant leak, but very very easy to shine a flashlight and check.

 

[YardPig]

You can shine a light down to your rear bypass, you will see it leaking with engine running if that is it. Here is a picture from when I replaced mine. You can see that vertical metal tube that is pressed into that cast piece. It will leak right at that press fitting. These often get damaged when the T’s get replaced because people are a little rough with them. I don’t think this is it, it’s usually a significant leak, but very very easy to shine a flashlight and check.

View attachment 1781220

View attachment 1781221

Do you happen to have the part numbers for the coolant cross over pipe and any gaskets if any? Looks like the perfect item to replace when my starter breathes it's last breathe!

 

[atnolan94]

Do you happen to have the part numbers for the coolant cross over pipe and any gaskets if any? Looks like the perfect item to replace when my starter breathes it's last breathe!

You are correct. If you do one of them do the other. You will also need the gaskets that go with it, I will look up the p/n. They are very very cheap. Sometimes the rubber portion of the gasket dries onto the block where the bypass sits. You need to scrape the excess and get new gaskets to prevent further leaking,

Coolant bypass:
16356-50120