'94 FZJ Another Mysterious Coolant Leak (above trans) (1 Viewer)

Joined
Oct 8, 2018
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Hi all, first Toyota, first time posting, have been reading MUD, mostly 80 series tech threads instead of books since I bought Chrundle in Oct. '18. I'll do my very best to stick to the pertinent facts (EDIT: In review I failed that last sentence so skip to end to avoid verbose back story):

Loaded up to hit the road the other day, I come out of the grocery and notice some green dripping from the trans pan.... Again. Last time it was PHH; Drained, replaced hose (did bypass w/ Gates Green Strip), flushed, hit the road the following day, stop at O'Reilly's to pick up the thermostat they forgot to include in my order the day of the flush (argh), dripping again. Young employee and myself quickly determined it's the straight coupling that replaced the T on the pass. side firewall line (rear heater bypass was done by one of the PO's). Let it cool down, replaced in the parking lot and off I went. Next stop, OH where my (grandpa's old) shop and most of my tools and materials actually live. Drained and flushed again for the purpose of swapping the T-stat. Tested both new and old T-stats, new opened right at 180° whereas old seemed to take it's time starting around 200°. I then proceeded to drive all over the place to the tune of 3k miles or so. No serious issues other than a small amount of detectable coolant loss via overflow level. Never dipped below the "low" (started from 2nd flush at about halfway between L and F) and rad stayed full (of Prestone premix and a somewhat alarming amount of the typical grey "gunk" FWIW).

Back to the present: standing in the rain in the grocery parking lot staring at this substantial drip-drop of Prestone from my trans pan I pop the hood, poke around and all I am able to notice is some green bleeding from that same pass. Side firewall line coupling (rear heater bypass) so I yank it out and just pop a single length of gates in place of the two short lines joined by coupling. Turn the key and the dripping resumes. Argh.

Ok, not going to the party in TN. I head back to "home" (western NC atm- we move a lot) and toss a pan under it to catch the drip. After it settles I have *maybe* 10-12 ounces of coolant in my pan but the rad is down much more, maybe a quart or two- presumably from the 8 minute drive home. I proceed to read everything I can possibly find on MUD that resembles my symptoms. Survey says Rear Heater lines rusted OR external HG blowout on #6. I resolve to spend the following day (yesterday) doing my first ever compression test. Buy the tool, warm up engine for a while and the dripping resumes -for 5-8 minutes- and then stops. I'm thinking it's gotta be the HG and it just closes up once warm. I've been paranoid about the HG for most of the time I've had the truck thanks to this forum of course, but have in the past year, done multiple block tests as well as two samples to Blackstone, all with good results. No yellow tester fluid, two good reports from Blackstone (I'm running Mobil 1 10-40), no milkshake (except for once during a really rainy week but it went away when the sun came back), spark plugs all look the same.

Anyhow, truck is warm, the drips stop. I do the compression test, six cranks per cylinder with multiple redo's. Fuel relay disconnected, distributor disconnected, throttle wide open. All cylinders clock in around 180psi on 6th crank INCLUDING #6 except for #2 which read at about 160. Side plot, I then attempt to wet test #2 but dropped two generous glugs of oil into the cylinder (instead of the prescribed 2 Tbsp or "cap full") only to get a PSI of around 240. Spent hours attempting to Google, siphoning and mopping the oil out, scared to death that I had hydrolocked the cylinder on the wet test. Did one more test after oil removal and still at about 200psi, then, for better or worse, decided to call it a day. Buttoned back up, turn key, all seems well. Little bit of that good burnt oil smell, engine sounds normal. I then drop it off at the shop I was recommended to here in WNC for a previously scheduled appointment to attempt to diagnose another issue which is a drivetrain whine and vibrations (only under load) it's had since I bought it. Will start separate thread for that if needed. So there it sits at the shop. I mentioned the drip to them and they said they would poke around but here's the deal...

Truck is at the shop because in two and a half years I haven't been able to pin down the sound/vibe (transmission shop in OH investigated it two years ago and said it's "probably fine for now") but other than that I am committed to doing everything I possibly can myself for both financial and educational purposes and whether or not they are able to locate source of coolant leak I'd rather not pay for repair if at all possible. Would rather do it myself.

Here are those aforementioned facts:

-Coolant is dripping pretty good on start up
-source seems to be above trans- it ends up on the pan shield then onto the ground
-drips also observed on rear heater lines (which have been bypassed by one or another PO) above cat
-seems to completely stop after 5-10 minutes of idle
-coolant loss in rad is significant on short outing
-can't find source of leak. PHH is holding, pass. side firewall line is holding.
-There is some wetness around the water pump.
-truck is generally messy. Started leaking from seemingly everywhere when I put in the Mobil 1 whereas before the only real leak was steering pump resevoir. I just keep oil topped off and call it "self changing oil" as was recommended to me by another overlander once. Not my preference but not ready to tackle all of these leaks at this time.
-have attempted to diagnose HG issue for months to no avail; four block tests (wouldn't catch external blowout), two Blackstone tests (about 2k miles apart, sodium was slightly high, they attributed it to possible additives from previous oil, potassium was normal, wear metals looked great for 230k engine, no significant increase in any numbers on second test, they seem to think it's in fine shape) and just yesterday a compression test where numbers were great except for #2 which was 20psi and 14% lower than the rest on round 1 (180, 160, 180, 180, 180, 180 or thereabouts). This also doesn't seem to me to point to #6 external blowout. Test was performed at about 2,500ft, 80ish degrees and maybe 60% humidity with a brand new $35 tool.
-FWIW I put on a magnaflow downpipe to an inline dual C.A.R.B. cat for a '95 setup. Custom job from first cat back done in OH. Later, another muffler guy in VA pointed out that it was 2" and seemed small. Is 2.5 stock? Too much back pressure? My truck is virtually silent.

Question: what am I missing? Why does my truck bleed green? (Other than it has green stuff in it instead of Toyota Red...)

Could a #6 blowout seal up under operating temp?

Since I put 315's on I've felt it to be sluggish but when I took all my camping gear and tools out to drive to the shop last night it actually felt pretty spritely so not sure what to think.

Hoping to sort this all out at warp speed as I have work travel coming at me in A FEW DAYS and my 80 is somewhat unfortunately serving as my DD at this time.

Help!

Pics of spark plugs and chicken scratch compression test results from yesterday included.

IMG_20210822_222138.jpg


IMG_20210822_165354.jpg
 
Joined
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Post a picture of the rear heater bypass on the firewall.

There's a coolant bypass hose under the intake manifold.


If your PHH was bad, then all your hoses are likely going bad. It would be smart to remove the intake, clean it, and replace *all* the hoses under there, along with all the other coolant and vacuum hoses in the engine compartment.
 
Joined
Oct 8, 2018
Messages
13
Location
Western NC
A few clarifications:

Most importantly I forgot to mention; had the AC charged (first time since owning) in VA last week and blasted ice cold 5hrs back to WNC. Went up to the Parkway the next day with gf and dog and the she noticed that the pass. Floor was soaking (and of course I just put the carpet back in when in OH a few weeks back). Didn't smell coolant-y at the time but now that it's at the shop I'm wondering.... Haven't rocked AC since then (last week).

That jumble of nonsense that is my compression test results (pic) should basically be viewed in such a way: the top row are the numbers as they occurred on round one. The "156" is how it looked immediately after cranking and the "160" was after I glanced the gauge again after marking the 156 but before letting the pressure back out. The bottom row is the summary after all the redo's including the final result on #2 AFTER removing as much oil as I was able. Also the engine had cooled pretty much all the way down at that point. So I would say row 1 has the most useful information. And yes, I generalized everything to 180 in my post whereas on the page it's a few 180's and a few 175's and such. I understand consistency to be the target result which is why I am only focusing on that #2 being on the low side. Rings?

I apologize for this post being soooo TL;DR and truly appreciate any help I can get as I appreciate this forum so much for helping me learn in the past couple of years, how to maintain and care for my Chrundle. This 80 may not be the greatest candidate for a restoration by a no-budget know-nothing but it's the 80 we've got and I'm going to do the best I possibly can.
 
Joined
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Messages
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Western NC
Thanks for the quick reply! Feeling better already.
Post a picture of the rear heater bypass on the firewall.
Will do as soon as I have truck back from shop. Probably Thursday. Knew I should have been taking pics all the while...
There's a coolant bypass hose under the intake manifold.

I learned of this in the general sense at the end of my PHH saga at which point it was time to fly and no more time to wrench. Of course it would pop up days before the next expedition. Thanks for the lead. I'm gonna jump right into that asap.
If your PHH was bad, then all your hoses are likely going bad. It would be smart to remove the intake, clean it, and replace *all* the hoses under there, along with all the other coolant and vacuum hoses in the engine compartment.
I agree with this 100%. It's amazing-bordering on paranormal- that this truck has given us two and a half years and 20k of adventures without a single serious issue while out in the wild. It only ever presents it's needs when I'm getting ready for a trip. For the record we have yet to get very far "out there". Cape Lookout, NC in April maybe takes the trophy so far...

One of these days I'll get myself set up for success and get on the front side of these issues at which point I'll proudly claim a routine of PM instead of always chasing things down under emergency conditions and when I do we will party.
 
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If your passenger floorboard is wet, I'd bet on the heater core or lines to/from it being bad. It a PITA to replace the core; you have to remove everything on the tunnel. I have a core that was working when it was pulled, if that is your problem.

Malleus the Younger is in Boone, not skiing as he intended to do when he moved there two years ago, but he is using my money wisely, so I'm not complaining. Much.

LMK if I can help with parts/advice/elbow grease from the minion. He has a few tools with him, most of what you would need, I would think.
 
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If your passenger floorboard is wet, I'd bet on the heater core or lines to/from it being bad. It a PITA to replace the core; you have to remove everything on the tunnel. I have a core that was working when it was pulled, if that is your problem.
This is a sweet smelling lead, pun optional. So I feel like a permanent noob here with no shame; what is "tunnel" in this scenario? Are there a range of possibilities as to why the pass. floor got wet? Seemed to coincide directly with first time using AC after charge; seems to have not gotten wet again since I've left the AC alone after initial incident- but I am still dropping coolant, mostly on startup, best I can tell...

Have failed to learn how that area (heater core) works. I know what a heater core is but I do not yet know about the ins and outs and how it is oriented with the AC. Is your core in Boone? Or you're saying you could ship? Will PM
Malleus the Younger is in Boone, not skiing as he intended to do when he moved there two years ago, but he is using my money wisely, so I'm not complaining. Much.
LMK if I can help with parts/advice/elbow grease from the minion. He has a few tools with him, most of what you would need, I would think.
My timeline is dire right now but if Malleus the Younger has time in the next several days to help me I will absolutely drop everything and head that way (I'm near Asheville) if it will place this episode in the rear view mirror for me. Must be in Staunton, VA mid day friday. In other words I am in absolute prime shape to be soliciting and accepting parts/advice/elbow grease from the minion, etc.

It seems to me at this time that the most important advice I seek is how to narrow down where the leak is coming from so I can use my time wisely in fixing it promptly. Advice on diagnosing heater core versus coolant bypass under intake? I'm sure it involves some simple scouting around which is impossible atm as the truck is at the shop but I will go take it from the shop today or first thing a.m. to deal with this problem first if that's what's going to get me down the road, drive line vibes and whine be damned.

-FC
 

mudgudgeon

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Most importantly I forgot to mention; had the AC charged (first time since owning) in VA last week and blasted ice cold 5hrs back to WNC. Went up to the Parkway the next day with gf and dog and the she noticed that the pass. Floor was soaking (and of course I just put the carpet back in when in OH a few weeks back). Didn't smell coolant-y at the time but now that it's at the shop I'm wondering.... Haven't rocked AC since then (last week).

If you're in the same humid weather as the Carolinas, and have been running AC on cold for any length of time, there'll be a lot of condensation created on the AC core in the heater box.
There's a drain at the bottom of the box to the outside to get rid of condensate.
Check that it is connected and not plugged up with mud, wasps nests etc

If it's not connected, water will leak on the carpet. If it's plugged, water will eventually find its way out of the heater box and onto the carpet.

Run the AC on full cold for a while in the humidity (an hour or so) and look for a leak . If the wet spot is cold immediately after running the AC, it's AC condensate.
 

zapatius

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Still have rear heater lines? Condition? They can develop pin hole leaks as they rust away. I lost quite a bit out of a tiny leak in one of mine because they're such a low point in the system.
 
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Still have rear heater lines? Condition? They can develop pin hole leaks as they rust away. I lost quite a bit out of a tiny leak in one of mine because they're such a low point in the system.
Rear heater had been bypassed by one or another PO. Awaiting return of truck from shop in order to obtain and post pics of said bypass per Gummycarbs' request. So upon reading another thread I noticed some folks talking about residual coolant finally rusting it's way out of the lines and considered that for a moment but it would, in my estimation, not be consistent with the conditions of my situation, mainly, only occurs while running and definitely results in significant loss of volume in rad.
 
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Confirmed: head gasket blown out externally on rear of #6 cylinder. The shop used a probe and figured it out rather quickly. It squirts coolant until it has warmed up a bit. Here we go...

Thank you all for the advice. It has helped me form an action plan. Hopefully in the coming months we'll be looking at much healthier 80.
 
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Confirmed: head gasket blown out externally on rear of #6 cylinder. The shop used a probe and figured it out rather quickly. It squirts coolant until it has warmed up a bit. Here we go...

Thank you all for the advice. It has helped me form an action plan. Hopefully in the coming months we'll be looking at much healthier 80.
Could be a freeze plug on the rear of the head.
 
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Could be a freeze plug on the rear of the head.
Thanks for the lead. I am going to call the shop and suggest this while it's still there. I scanned the "freeze plug" threads that came up on a quick Google search and notice there are a number of folks who have experienced this on one of the driver's side freeze plugs on the block (also cracking:() but didn't turn anything up on my quick search regarding the one on the rear of the head.

Is there also one on the rear of the block? Could this also be the potential culprit?

What would be the procedure for repair if a rear facing freeze plug? Surely one would need to pull the engine to deal with this....(?)

Sounds maybe more tedious than HG replacement?
 
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Thanks for the lead. I am going to call the shop and suggest this while it's still there. I scanned the "freeze plug" threads that came up on a quick Google search and notice there are a number of folks who have experienced this on one of the driver's side freeze plugs on the block (also cracking:() but didn't turn anything up on my quick search regarding the one on the rear of the head.

Is there also one on the rear of the block? Could this also be the potential culprit?

What would be the procedure for repair if a rear facing freeze plug? Surely one would need to pull the engine to deal with this....(?)

Sounds maybe more tedious than HG replacement?
There's a thread here on a guy that had only water in the truck he bought, transported it up north, it froze and blew out the plug in the rear of the head. He still had to pull the head to get to it, though. I don't recall the handle or the thread name.
 

zapatius

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Thanks for the lead. I am going to call the shop and suggest this while it's still there. I scanned the "freeze plug" threads that came up on a quick Google search and notice there are a number of folks who have experienced this on one of the driver's side freeze plugs on the block (also cracking:() but didn't turn anything up on my quick search regarding the one on the rear of the head.

Is there also one on the rear of the block? Could this also be the potential culprit?

What would be the procedure for repair if a rear facing freeze plug? Surely one would need to pull the engine to deal with this....(?)

Sounds maybe more tedious than HG replacement?

I can confirm there are two freeze plugs on the back side of the head. Mine froze and popped one out. Also cracked the head in six places. Don't have to pull the engine to repair, just the head. Same as you would for a head gasket.


20210217_215005.jpg
 
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BILT4ME,

I asked the shop if it was possibly a freeze plug and they explained to me that they narrowed the squirting coolant down to the seem between the head and the block, and it's definitely the head gasket. Said it was visually unmistakable. I have not been able to look myself.
 
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BILT4ME,

I asked the shop if it was possibly a freeze plug and they explained to me that they narrowed the squirting coolant down to the seem between the head and the block, and it's definitely the head gasket. Said it was visually unmistakable. I have not been able to look myself.
Yes, that's possible.

Make sure they only use Toyota parts to rebuild for the HG stuff.

Was worth a discussion.
 

zapatius

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BILT4ME,

I asked the shop if it was possibly a freeze plug and they explained to me that they narrowed the squirting coolant down to the seem between the head and the block, and it's definitely the head gasket. Said it was visually unmistakable. I have not been able to look myself.

Even if it is the freeze plug, you're going to do all the same things you would to replace the head gasket. Mine poured coolant out the back, down the trans tunnel and hit the ground around transfer case. It was a sizeable leak.
 
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Well, I'm still in the middle of a HG replacement and have yet to discover the true origin of my leak despite my greatest, albeit sporadic efforts. When I got down to the old gasket a mechanic buddy and myself determined there to be no evidence whatsoever of any leaking from the gasket or the freeze plugs on the back of the head, despite the certainty asserted by the shop who did the diagnosis. He (mechanic buddy) had no further ideas and was only helping me out here and there while he was in the vicinity of my work location doing other stuff. The machine shop (different shop, to be clear) where I took the head found a crack near the rear side of the #2 cylinder on the exhaust side. Why? Whole other can of worms. I am not clear if the crack penetrates to anything as it appears on the outside corner and I am unfamiliar with the way in which water channels through an engine head beyond what I can see when observing my nice clean cracked head. I found a replacement and it has been inspected and serviced and is ready to go in the truck. Getting organized and cleaned up and close to reinstall but I can't for the life of me figure out the source of the leak that began this whole fiasco...

The rear heater lines have been bypassed since I got the truck and even if they have anything in them still, it is clear the coolant is coming from elsewhere as it lowers the level in the rad rather quickly, as in a quart every 15-25 minutes of country road driving upon most recent test. Again, very drippy off the trans. Also I've visually inspected the rear heater lines to find that while rusty, they present no evidence of current/recent leaks. Might rip em out if I have time.

Are there ANY other lines that would drop coolant onto the top of the transmission/bell housing? Could a leaking heater core make it's way to there without leaking into the cabin? At all? PHH replaced recently, holding fine, heater control valve, all the heater lines all seem fine. Could the head having been cracked by #2 exhaust side have created a leak on the other end of the motor that would have been observed as "spraying"? Could coolant from a crack on the exhaust side @ #2 or the water pump blow clear back to the bell housing and roll down onto and subsequently off of the trans without also dripping off the block as well? Seems unlikely to me. So excited to figure it out.
 

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