Coolant Leak Troubleshooting Steps (1 Viewer)

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Checked my fluids this weekend, and noticed my coolant reservoir was pretty much empty. There is just a thin line of red or pink at the very bottom of the reservoir -- well below the Low line.

So, I have some sort of coolant leak. Would love any tips on how to go about troubleshooting to find the actual leak.

I have receipts from previous owner that Heater Ts were replaced about 6,000 miles ago. So in about 18-24 months, it has leaked out.

No idea if the hoses have ever been replaced. I was going to order the two radiator hoses (16571-50150 and 16572-50150) as well as the four clamps, and get some Toyota Red from the dealer as a starting point.

Is it as simple as doing a coolant flush, cleaning up the hoses and clamps areas (so new leaks would be more noticeable), and then wait to see if more red leaks appear?

Here's some photos which are what's leading me to replace the radiator hoses first:
IMG_9876.JPG

IMG_9877.JPG


IMG_9878.JPG


IMG_9879.JPG


Have read some threads I've read:



My understanding of flush process (never done this, learning, so just verifying):

Tools needed:
  • 1/4" or 5/16" interior dimension clear tube
  • 10mm socket
  • Lots of distilled water (~12 gallons to be safe?)
  • 2 (or 3 to have extra?) gallons of Toyota Red coolant
Steps:
  1. Attach tubing to block drain cocks and into empty 1 gal container
  2. Loosen bolt with 10mm socket
  3. Once empty, tighten bolts back (block bolts = 9 ft/lb, radiator = hand tighten)
  4. Empty radiator from bottom in same manner
  5. Fill with distilled water (~4 gallons?)
  6. Turn engine on until reaches operating temperature with heater on high to get everything flowing into the engine
  7. Turn engine off -- allow to cool
  8. If what drains is not clear water -- repeat steps 1-7, then continue to step 9
  9. Re-check all drains are closed
  10. Anticipate ~1 gallon of distilled water still in system, add 1 gallon Toyota Red concentrate to radiator (to bring up to 50/50 mix of 2 gallons in system)
  11. Mix 1 gallon Toyota Red with 1 gallon distilled, add to radiator (rookie question: do you have to mix it in a separate 2 gallon container, or can you add them individually and it will mix in the system?)
  12. Secure radiator cap back on
  13. Turn engine on, get to operating temp, turn off, check reservoir. If below full, add more 50/50 mix.
  14. Repeat 12 and 13 until stays at full.
  15. Check reservoir periodically over next few days to make sure stays at full.
  16. Properly recycle old coolant.
And in my situation -- after the first drain, go ahead and replace the two radiator hoses since they've likely got coolant/crud/etc in them -- so put new ones on before first flush with distilled water?

Thanks -- know this is long, just don't want to get into the middle of doing this and have missed a step or realized I needed some other part, extra coolant, etc.
 
Last edited:

awesomeissquid

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Your process looks pretty much correct. Yes I would replace the hoses before you start the flushes.

You should only need the two gallons of Toyota Red. When you are refilling with them for the final fill you should have the 1 gallon of distilled in the system, then add the two gallons of T-Red, then top off with whatever distilled is needed to get you full.

One thing you can do since you will be flushing everything (12 gallons of distilled), is pull the thermostat valve so you don't have to wait for the engine to heat up before it opens and the water is cycled through the whole system. You can do this for all the distilled water cycles and then replace it for the final fill. It might be good to go ahead and replace the thermostat and gasket if you don't know the age on it.
 
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Your process looks pretty much correct. Yes I would replace the hoses before you start the flushes.

You should only need the two gallons of Toyota Red. When you are refilling with them for the final fill you should have the 1 gallon of distilled in the system, then add the two gallons of T-Red, then top off with whatever distilled is needed to get you full.

One thing you can do since you will be flushing everything (12 gallons of distilled), is pull the thermostat valve so you don't have to wait for the engine to heat up before it opens and the water is cycled through the whole system. You can do this for all the distilled water cycles and then replace it for the final fill. It might be good to go ahead and replace the thermostat and gasket if you don't know the age on it.
Thanks. Probably going to buy a pressure tester to make sure I'm ordering the correct hoses, too. Ordering from PartSouq and want to make sure I'm not missing a hose I need. Essentially if I am going to pay for shipping, make sure I'm getting all of the right parts.
 
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Personally I would clean everything up, top off the coolant, and then pinpoint where the leak is before you throw money and time at everything.
Yea I cleaned up those two hose connections so if that's where the leak is it will be more obvious, filled the reservoir to about 1/2 with distilled water, bought a tester from Harbor Freight, opened the box and the quick connect fell apart... so going to take it back tomorrow and head to Advance to get a loaner. I thought the tool loan stuff had a cost, but looks to be absolutely free.
 
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Now I'm just confused.

Got the tester from Advance. Got it hooked up correctly. Got it up to 12 PSI. Held 12PSI for 10 minutes. No signs of leaking, anywhere. No drips, no wetness, nothing.

Only lost coolant was removing the tester - couple of squirts around the radiator, cleaned those up.

Should I just get engine at operating temp, turn off, and top off the reservoir to full and monitor?
 

awesomeissquid

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The vehicle is pretty new to you right? Is it possible it has just always been low and not actually leaking? Maybe they didnt properly burp the system when they replaced the T's?
 

2020 Rocks

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When searching for a leak you may want to check out the oil cooler bypass hose, it goes into the housing that holds the oil filter. It runs up the front from there to the top of the engine, four hose connections from top to bottom.
 
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I think radiator PSI limit is what, 15? 16? Should I reattach everything and push it up a few PSI? I figured 12 was pretty close and I didn't want to go too far (no rating on my cap that I can see).

The vehicle is pretty new to you right? Is it possible it has just always been low and not actually leaking? Maybe they didnt properly burp the system when they replaced the T's?
Had it about a year, only put about 2700-2900 miles on it due to the pandemic. Maybe... but man, I am almost certain the reservoir was at least half full when cold. I think I would've noticed it was almost empty with just a hint of pink at the bottom, but now I doubt myself!

When searching for a leak you may want to check out the oil cooler bypass hose, it goes into the housing that holds the oil filter. It runs up the front from there to the top of the engine, four hose connections from top to bottom.
Will do, thank you.
 
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Personally I would clean everything up, top off the coolant, and then pinpoint where the leak is before you throw money and time at everything.
I like this method best. No sense in pressure testing yet, clean it all up and top it off and go from there.
 

87warrior

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You are absolutely loosing coolant at these two spots. The red coolant makes it real easy to spot.

It also looks like at least one of the hoses at the heater T is swollen.
Screenshot_20210413-163309.png

Screenshot_20210413-163124.png
 
Joined
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You are absolutely loosing coolant at these two spots. The red coolant makes it real easy to spot.

It also looks like at least one of the hoses at the heater T is swollen.
Yea, noted, and the one heater pipe is swollen. Thanks for pointing that out, wasn't sure if that was normal or not.

Since I'm dealing with a lot of unknowns here -- not sure if these have ever been replaced, I'm thinking just go and replace everything via PartSouq. I might feel differently if I were paying dealer prices, but here's my thinking.

Fall 2022 we are planning to drive across the country with our kids for 4-5 weeks for Yellowstone, Rocky Mountains, Moab, Grand Canyon, etc. Between now and then I'd like to try some easier trails in east TN/west NC/southwest VA.

I could order just the two radiator hoses, clips, and maybe the one swollen heater T pipe for about $100 including ~$45 shipping (and that's still cheaper than my local dealers and online dealers).

But I'm already in for shipping at that point. If I add in what I think is every single cooling system hose, clamps/clips, plus PCV valve and grommet, some bolts for the underengine pan, new thermostat and gasket, new radiator cap, and even two new heater Ts (even though it was done < 10k miles ago, they're $5.06/ea so can replace and use the recent replacements as emergency spares)... my all-in shipped cost is $384.26. Only thing not replaced is the reservoir.

Seems like $285 is cheap insurance (cost of an expensive, middle of nowhere tow?) to make sure I'm not on the side of the road in the desert of Utah or Appalachian mountains kicking myself because I only replaced 2 or 3 hoses instead of doing them all while the coolant is drained anyways.

Might come off as a "throw money at the problem" but besides having to do more work, not seeing downside to just going in on everything. Again, if I were paying dealer markup and it was $100 vs $1,000 I'd probably feel different.

So, looking at all of the part diagrams, here's my list below.

Saw this post but some of the part #s aren't lining up for my August 1999 production date 2000 LC... can someone check this list? Brain is going to mush looking at all of the part diagrams. Also, I'm fairly confident the number of clamps/clips is correct, but since they're so cheap I'd probably add 1-2 of each just to make sure in case I'm off from a count standpoint or if I break one somehow, spares, etc.

Part #
quantity
PartSouq (each)
PartSouq Total
16572-50150​
lower radiator hose​
1​
19.11​
19.11​
16571-50150​
upper radiator hose​
1​
13.49​
13.49​
90467-43002​
radiator hose clamp​
1​
2.74​
2.74​
90466-41008​
clip hose​
3​
2.80​
8.40​
90480-18001​
PCV Valve Grommet​
1​
2.47​
2.47​
12204-50020​
PCV Valve​
1​
9.58​
9.58​
90119-08862​
Bolt with washer​
6​
1.40​
8.40​
90916-03100​
Thermostat​
1​
13.98​
13.98​
16346-50010​
Thermostat gasket​
1​
2.22​
2.22​
90467-20011​
Water bypass hose clips​
6​
1.60​
9.60​
16281-50030​
Water by-pass No 4​
1​
5.02​
5.02​
16282-50040​
Water by-pass No 5​
1​
4.47​
4.47​
16261-50090​
Water by-pass​
1​
3.50​
3.50​
90467-13054​
Clamp for water by-pass hose (replacement for previous part #90467-13059)​
2​
0.60​
1.20​
16401-67150​
Radiator cap​
1​
12.30​
12.30​
15777-50030​
Hose, oil cooler​
1​
12.83​
12.83​
87248-60460​
Heater T Connector​
2​
5.06​
10.12​
99556-20200​
Hose, Rear Heater Water Inlet B, Outlet B, outlet C? (buy 3?)​
3​
3.83​
11.49​
96136-42501​
Clamp for water by-pass hose No 2 (for heater core hoses)​
8​
2.22​
17.76​
87245-6A090​
Hose, rear heater water inlet c, outlet A? (from heater unit)​
2​
14.33​
28.66​
87245-6A201​
Hose, Rear Heater water inlet A (from engine)​
1​
13.18​
13.18​
87245-6A180​
Hose, heater water, outlet A​
1​
9.95​
9.95​
87245-6A060​
Hose, heater water, outlet A​
1​
21.01​
21.01​
87245-6A210​
Hose, heater water, inlet B​
1​
7.68​
7.68​
87245-6A070​
Hose, Heater Water, Inlet A​
1​
15.57​
15.57​
87245-6A220​
Hose, Heater Water, Inlet A​
1​
10.87​
10.87​
87245-6A190​
Hose, Heater Water, Outlet B​
1​
15.97​
15.97​
96136-52101​
Clamps for Inlet and Outlet A (4)​
4​
1.97​
7.88​
16405-50020​
Cap sub-assembly, reserve tank (cap, 2 hoses, 2 clips)​
1​
17.35​
17.35​
 
Last edited:

jerryb

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I didn't check your parts list, but if replacing heater tee hoses, reuse the zinc coated clips compared to the black colored clips you'll get new from dealers or PS. If they haven't been off more than twice there shouldn't be a problem. That's another easy way to tell if someone has changed any of those, that and the red or white slash on the hoses themselves.
The black clamps are smaller than the originals and more difficult but not impossible to use on any of the tee hoses.

I just had the two hoses off that go down to the rear water bypass on the engine and went back to the 4 original clamps from 4 years ago with the engine back in. Truthfully I had to Dremel the clamps the get them off, even with proper spring clamp pliers.

I prefer the pressure tester to save time. Much better than running the car. Like they said though, fill and watch.
check your clamps on the 2 big radiator hoses, they are different sizes. I didn't like reusing those more than twice when I had radiator damage problems.

What I did was just press the radiator to 15psi with new cardboard under the car, and wait. That was my final method on radiator #3.
 
Joined
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I didn't check your parts list, but if replacing heater tee hoses, reuse the zinc coated clips compared to the black colored clips you'll get new from dealers or PS. If they haven't been off more than twice there shouldn't be a problem. That's another easy way to tell if someone has changed any of those, that and the red or white slash on the hoses themselves.
The black clamps are smaller than the originals and more difficult but not impossible to use on any of the tee hoses.

I just had the two hoses off that go down to the rear water bypass on the engine and went back to the 4 original clamps from 4 years ago with the engine back in. Truthfully I had to Dremel the clamps the get them off, even with proper spring clamp pliers.

I prefer the pressure tester to save time. Much better than running the car. Like they said though, fill and watch.
check your clamps on the 2 big radiator hoses, they are different sizes. I didn't like reusing those more than twice when I had radiator damage problems.

What I did was just press the radiator to 15psi with new cardboard under the car, and wait. That was my final method on radiator #3.
Thanks for the insight. Got a closer pic of the heater t yesterday. Looks like maybe 3 zinc clamps and a screw/spring type?
68D6B5AA-34EE-4287-929A-4375FBAEDB1C.jpeg
 
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Signs point to heater Tees have been replaced, but not hoses. It's fine to reuse heater hoses if not swollen and a snug fit. I clean them with lexol vinylex outside and into hose ends. The stuff has a plasticizer, which helps condition and protect rubber. When reusing hoses, Toyota recommends placing clamps back in same position. The old hoses have impression from old clamps which makes orienting clamps easy. I can see your old impression, which indicates old hoses and clamps just put back for easy access rather than best orientation. When hoses are replaced, than we can place clamps as we like to make easy.

The first hose has a screw clamp on it. Likely it leak with factory clamp after heater Tee replaced and was subsequently replaced. I'd consider replacing the one hose and one clamp. Since others not leaking, leave them alone. Even it can stay for now, as it's not leaking. But that type of clamp is damaging to hose.

IMG_9878.JPG

These 2 radiator hoses appear to have leaked at some time. Your pressure test indicates not leaking now. So likely the coolant has been eating aluminium. The byproduct gunked-up and stopped leak(s). But unfortunately you'll likely find pitting (impression) in hose and pit in/on aluminium of water inlet cap and water bypass joint front goose necks.

Water bypass joint front, goose next.
Screenshot_20210413-163124.png

Water inlet cap.
Screenshot_20210413-163309.png


I'd also be inspecting both front and rear water bypass joints at 4 bolting points. Look for leak signs, before cleaning engine.
Additionally look at water inlet where it attach with large O-ring to water bypass joint front. If you see signs of FIPG (very bad practice) used at round O-ring seal point. You may have pitting there also. Pitting in water bypass joint, and possibly under O-ring in water inlet.

You've 3 choice with pitting.
  1. Do nothing. In which case coolant will get into pits and continue eating. At first minor leaks, that may clog themselves. Eventually the pits will eat through aluminum.
  2. Clean-up and banded. I consider this temporary, But done right can last for a very very long time. I use this when parts not available in time frame needed. Or in case of front water bypass joint on VVT. The non VVT we can pull throttle body and R&R water bypass joint. In VVT it requires removing intake manifold. So I temp band-aid until the day I've have other reason like starter or A.I service to pull intake manifold of the VVT engine.
  3. Replace hose and all pitted aluminium.
Here my band-aid with Toy 1282B FIPG. Trick is to get supper clean, scrape flush only filling pits and let cure ~24hr's. This example is on block (non replaceable part), but technique is the same.

Here's few examples of pitting.

This is under O-ring on water inlet.
IMG_1376.JPEG


Rubber hoses seem to have more of a deep impression. I'm not sure if they'd actually get eaten. But coolant will get in impression (pits) leak and cause electrolysis to eat aluminium.

041.JPG
 
Last edited:
Joined
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More examples of leaks and pitting

Signs of coolant leaks at PS front water bypass joint:
Coolant leak detection cleaning (7).JPG

Pitting on head under water bypass joint.
065.JPG



OUCH head gasket leak
Head gasket.jpg

Other leak point and water bypass joints location.
Rear & front water bypass joint.jpg


Check hose going to and coming from oil cooler (between oil filter and oil pump.

Lexus dealership repaired these oil cooler hose leaks, with aftermarket hoses and clamps. All leaked again.
011.JPG
 
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Water inlet O-ring assembled with FIPG wet. Very bad. Coolant get into pocket created by FIPG and starts eating away.
IMG_6775.JPEG

IMG_6779.JPEG


IMG_6838.JPEG


Assembling with bad hoses, inlet cap can get very nasty.
IMG_6083.JPEG


For the most part all coolant damage, is due to improper PM and or improper service by shops or DIY.
 
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For the most part all coolant damage, is due to improper PM and or improper service by shops or DIY.
So if we can get by with 1 vehicle for a while, are you saying I should 1. drain coolant, 2. disconnect all hoses and check for leaks, pitting, etc. on the front and rear water by-passes? (Or would that necessitate having replacement gaskets on hand)?, and then 3. order all parts I'll need?

I work from home and we have 2 vehicles, so not a deal breaker if I had to take some things apart then order parts from Dubai and wait a week for them to show up.

Or, set up tester at 15PSI, leave cardboard, wait for leaks to show, and then do the above?

I guess I'll follow the first above advice from @jerryb -- remove the underengine pan, put down clean cardboard, reconnect the tester at 15PSI, and wait. (Question: How long is long enough!) before doing anything else.

I mean, even if there was heavy pitting on the by-passes and front inlet, adding those, 4 gaskets, even the nuts (bolts not available at PartSouq)... it would bring the total to $533.90 $562.50. With my context of wanting this LC to run for a long time and not strand me on any adventure trips, that seems like a small price to pay (IF I had to replace the by-passes, inlet, etc, not just doing just because). I shudder to think what it would cost to have a dealer or shop do this... think the dealer charges something like $128/hr...
 

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