Chasing a Slow Coolant Leak – 1996 80 Series, 190K, HG Done

[LimitingFactor]

Finally got around to blowing apart the cooling system. None of the gaskets appear be failed Pressure tested the cooler and it checked out fine. There was one suspicious hairline crack on the oil pressure relief galley of the aluminum housing so I am debating leaving it, jb welding it, or get a new housing?

 

[Marvelicious]

If it were me, I'd do a dye penetrant test on that to see if it's anything, because it kinda looks like it could be just a surface flaw and might even be from the mold, not actually a flaw in the part. You might watch a few youtube videos to explain the process, but it's not super complicated. I'd go for "water washable" dye, and wash it thouroughly. If it's really cracked, it'll be pretty obvious. If you wind up in doubt, post the pics. A few bucks in chemicals from the local welding shop will tell you whether you have something to fix, or not.

Alternatively, someone who knows what they're doing with a TIG torch could just grind a little groove there and fill it with fresh metal. Still, better to only fix it if it's actually a problem, which brings me back to my first idea.

 

[Kernal]

Can you circle the area you think has a crack?

Did you find any coolant residue on the outside of the cooler cover?? The interior appears to have zero corrosion which seems
to be where some leaks start.

 

[LimitingFactor]

Good point about a dye pen test, I don't have a kit and they only cost a little less than what a new OEM housing runs..
The area in question is circled:

 

[Marvelicious]

Good point about a dye pen test, I don't have a kit and they only cost a little less than what a new OEM housing runs..
The area in question is circled:
View attachment 4178953

To me, it's just something worth keeping on the shelf, but if you're only likely to use it once, and the OEM housing is that cheap, I'd just replace it, but I really don't think that's anything. Still, I'd want the peace of mind.

Another idea: Get a couple of rubber plugs to fit the holes, drill one to fit an air nozzle, and pressure test it with soapy water...

 

[LimitingFactor]

I decided to move forward with reassembly. I made a few block off plugs to pressure check the oil cooler and just re used them for the housing. I dunked the housing in water while pressurized and didn't see bubbles so I'm confident now it wasn't a crack.
Still doesn't confirm where the original leak is though? I'm also doing a rear heater delete, water pump and PHH while the system is drained and apart.
I'm going to drive it for a while and see if this fixed the issue.

 

[Marvelicious]

Glad to see the 'ol calibrated eyeball is still calibrated. Still, it sucks that you're still hunting for the problem.

 

[Kernal]

Nice custom made leak/pressure test tool

 

[ADP91]

Hi LimitingFactor,

I had this exact issue - ironically on a similar timeline (last fall till now). I was losing a steady but small amount of coolant with no external leaks. Did a Blackstone analysis and confirmed coolant contamination and did the combustion gas coolant test (radiator neck) and it came back negative.

My compression/leak down test results were pretty bad so I decided to take it in to a local shop for HG replacement and inspection. What they found was a crack in the cylinder head. So we ordered a new OEM head from Toyota ($3500 CAD plus shipping). The engine is back together and it appears the issue is resolved.

Probably not the news you want to hear by just wanted to share my similar experience.

Let me know if you have any questions.

 

[MissahPapaJ]

Really cool idea making those block off test ports!

 

[MissahPapaJ]

Hi LimitingFactor,

I had this exact issue - ironically on a similar timeline (last fall till now). I was losing a steady but small amount of coolant with no external leaks. Did a Blackstone analysis and confirmed coolant contamination and did the combustion gas coolant test (radiator neck) and it came back negative.

My compression/leak down test results were pretty bad so I decided to take it in to a local shop for HG replacement and inspection. What they found was a crack in the cylinder head. So we ordered a new OEM head from Toyota ($3500 CAD plus shipping). The engine is back together and it appears the issue is resolved.

Probably not the news you want to hear by just wanted to share my similar experience.

Let me know if you have any questions.

View attachment 4180017

Was that the install price? 3500$ or just the head? When you did the head did you do new cams and everything or did you swap things over?

 

[ADP91]

Was that the install price? 3500$ or just the head? When you did the head did you do new cams and everything or did you swap things over?

$3500 was just the head I believe. Machine shop had to replace the cam with a used one as it had a small crack in the end. Was already planning new valves, seats, springs, etc. so that went into the new head. So essentially everything new except a used but good cam.

 

[MissahPapaJ]

$3500 was just the head I believe. Machine shop had to replace the cam with a used one as it had a small crack in the end. Was already planning new valves, seats, springs, etc. so that went into the new head. So essentially everything new except a used but good cam.

Contemplating a new head, my head gasket has been done but I don’t know the 5W’s about it all I do know is I didn’t do it so I don’t know the quality of work done and what corners were cut. I can get a head from Toyota for 1600$ and I’m positive my only good machine shop in the area is more in labor than the cost of the head from Yota ( my local machine shop while they do excellent work is too expensive )

 

[HuyFZJ80]

Feels like Déjà vu reading this thread. Had similar issues with coolant loss. Leak down test was negative. No milky oil. No visible loss of coolant. Compression tests were good. I had some white smoke in the cold mornings, but had shrugged it off to condensation. Blackstone test showed some minor amounts of coolant in the oil. Did the oil cooler first and it didn’t change anything. Finally just tore into a head gasket change for peace of mind, and found the culprit. Failed HG, just enough to lose coolant but not a catastrophic failure.
I hope you find your solution, as it feels all too familiar to me. Haha

 

[LimitingFactor]

Update: The oil cooler wasn’t it

I’ve put roughly 400 miles on it since reassembling everything, and unfortunately the coolant loss is still there. I’ve gone through about a gallon of coolant over those 400 miles.

So, unfortunately, the oil cooler did not fix the issue. I’m also still not seeing any obvious external coolant leak, which puts me pretty firmly back into the “coolant is getting into the engine” camp.

At this point I’m thinking the most likely culprits are:

* Head gasket
* Cracked cylinder head
* Cracked block

The frustrating part is that this continues to behave like a very slow internal leak rather than a catastrophic failure. The cooling system holds pressure, there’s no obvious external leak, and the oil cooler/housing has now been thoroughly pressure tested and ruled out.

There have been a couple reports in this thread of very similar symptoms ultimately being traced back to the head gasket or a cracked head, so unfortunately I’m starting to think I’m headed in that direction.

I’ll probably do some additional testing before tearing into it, but at this point it’s looking increasingly likely that the head is coming off or pulling the engine so I can address a rear main leak as well.

The saga continues...

 

[Fj80oregon]

Pull your valve cover and plugs, remove your t stat, pressurize the system over night and see what happens. Check your head for cracks around the 5 Allen head plugs in the head, and look down each cylinder with a bore scope to see if you can see any leaks. It has to be going somewhere.

 

[petegangies]

Update: The oil cooler wasn’t it

I’ve put roughly 400 miles on it since reassembling everything, and unfortunately the coolant loss is still there. I’ve gone through about a gallon of coolant over those 400 miles.

So, unfortunately, the oil cooler did not fix the issue. I’m also still not seeing any obvious external coolant leak, which puts me pretty firmly back into the “coolant is getting into the engine” camp.

At this point I’m thinking the most likely culprits are:

* Head gasket
* Cracked cylinder head
* Cracked block

The frustrating part is that this continues to behave like a very slow internal leak rather than a catastrophic failure. The cooling system holds pressure, there’s no obvious external leak, and the oil cooler/housing has now been thoroughly pressure tested and ruled out.

There have been a couple reports in this thread of very similar symptoms ultimately being traced back to the head gasket or a cracked head, so unfortunately I’m starting to think I’m headed in that direction.

I’ll probably do some additional testing before tearing into it, but at this point it’s looking increasingly likely that the head is coming off or pulling the engine so I can address a rear main leak as well.

The saga continues...

I personally wouldn't call that slow coolant loss... in Aussie terms, that's nearly 3.8L in 644km.. that to me is more than slow. Yet it sounds like you're not getting any mixing between oil and coolant (but you sort of did, as your rad cap had that gunk under it), or smoke, but as you mentioned, many have had this mysterious slow coolant loss without all the other symptoms and it progressively got worse over 10,000kms and inevitably was the head gasket.

I lost about 400ml of coolant over 4,000kms from the overflow bottle (radiator always full).. that is pretty slow, but like you, I haven't identified the cause yet. Cooling pressure test is okay, new radiator, all new hoses etc. My oil analysis was all good too.

I've just replaced my radiator overflow bottle as the previous one had a hole in the top for a cheap aftermarket sensor with probes for level detection. The hole wasn't sealed properly and I could see some minor evidence of red coolant dripping out. So maybe over time with it sloshing around and evaporation, it could explain my loss. Now with the new bottle I'll track it over the next few thousand kms and see if it continues to slowly drop.

Did you end up doing an oil analysis?

 

[Kernal]

All the above, might also help (to find leaks/cracks) by adding a UV dye to the Radiator/coolant if that hasn't been tried yet.

 

[LimitingFactor]

Thanks all, good points.
@Fj80oregon I'll see when I can pull the valve cover and do another pressure check
@petegangies I did an initial Blackstone analysis before the tear down and they confirmed coolant in the oil, I haven't put enough miles on it yet to do another round of testing but I'm planning on it.
@Kernal good call I will look into that.

 

[Brindleboxer]

Odd question but when you had everything apart did you ever go back and check #4? I didn't see a post about that.

Also, assume you checked your overflow tank for a possible source for the leak as well.

Like Kernal said I would try the dye and see if you can see any residue/trail.