Mystery coolant loss - put on your thinking caps....

[IdahoDoug]

Before I get started, I'd like to extend thanks across the miles to Cdan, who's been helping me try to figure this out - even yakking with me this evening while at home (hope you got back to your movie and enjoyed it despite the interruption).

Put on your thinking cap.

My 97 has been losing coolant at a pretty good rate. I looked things over, found the fancy silicone PHH hose weeping, and a couple heater hoses also weeping. Stopped the PHH, took another try to stop the heater hose, which you read about when I inquired about anything to make a hose stick on better a couple days ago. Jammed paper towels around these things today and drove around town for half hour of short trips.

Got home, and it used perhaps a half pint of coolant, yet all the paper towels are dry. No question - coolant was lost/gone.

Got three different flashlights and methodically went over the entire engine bay (already did this several times), spending over an hour just looking. No head gasket external leaks. Even looked at the rear heater metal lines, felt the carpets, etc. Nothing. Checked over the radiator (new 7000 miles ago). Not coming out the radiator cap (new, also). Not coming out the overflow cap (new, also). Then I found a large leak on the large upper radiator hose block end. Cannot believe I had not noticed this before. Looks like a defective hose as it's oozing out the threads (new, also).

Idled the truck for 15 mins - no dripping. Then stuck a screwdriver in the throttle at 3200 rpm and waited for that upper hose leak to start dripping. It wouldn't, so I gave up and will just replace it. I was hoping for some combo of warm or cold or high rpms that would cause it to start flowing enough to make me happy I'd found the source of a loss of coolant that has now amounted to near 3 gallons over the last couple months. No such luck.

That's when the fun started. I'd shut down the truck and was laying under it just waiting for SOMETHING to start dripping. Suddenly realized I was listening to the faint sound of water boiling. Hmmm. Slid toward it and listened until I was directly under the cats (this is the 97) and could plainly hear what sounded like the constant sound of boiling/sizzling water. Not good. After a minute it stopped. On a hunch, I went to the tailpipe. It was completely soaked inside and dripping enough that a 3" diameter puddle was on the ground. I could plainly smell coolant, but the stuff on the pipe and ground was plain water. No question about the coolant smell as 10 minutes later I literally stuck my nose in the pipe end and could still smell it plain as day.

This is when I called Dan to ask if he'd ever heard of a cracked block or any other way of coolant getting into the exhaust BESIDES a head gasket. When I put new plugs in it a few months ago, they were all uniformely dirty - no clean plug indicating coolant in the cyllinder. And since then it's gotten low on coolant once, but not overheated due to this leak. We commiserated on the phone, and I told him I'd call back after pulling the plugs as we both felt that I'd gotten unlucky and the truck had blown the HG of its own accord. He went through a mental list of what he had on hand for a complete HG kit that could go out Monday.

Pulled the plugs - nothing. I don't mean maybe/maybe not. I mean absolutely identical sparkplugs without a trace of difference under a 600W light. Even looking deep into the base of the ceramic for the faintest water drop or rust speck. Looked in each plug hole and saw nothing but normal black/brown piston tops including #6 which took a mirror to see into. Nothing again.

Called Cdan and heard the strange sound of knitting needles hitting the floor I heard with the starter episode. Hmm. Seriously, there were a lot of long silences on the phone as we thought it through.

So, I'm going to FedEx an oil sample to Blackstone to see if they find any coolant in the oil. And when I get done typing this I'm going to go out in the garage and button up the engine and simply drive the truck as I cannot figure this out.

Oh, and one other bizarre mystery. Took the oil cap off and it was so hard to get off I was about to get a pair of pliers. All the way off, not just breaking it loose. Wasn't cross threaded - threads look fine. Tried to put it back on, and it will only go on a turn or so before it simply locks up. Grabbed the 93's and it spins almost all the way down to the gasket seating with a flick as always. Bizarre - I'll order a new one.

So, that's where I'm at. Boiling something in the cats, definite coolant smell at the tailpipe after shutdown. No smoke/steam when I drive it. Losing a lot of coolant the minor seeps I found don't seem to explain. What do you folks think??

One thing Dan and I both wondered was how fast will coolant in the cylinder clean things up so you can see a difference. My impression was this is an almost instant phenomenon. Not a week of driving, not a day, but literally in minutes the cylinder would be steam cleaned dramatically. Anyone know more about this effect?

Thanks for reading this long!

Regards,

DougM

PS - did a compression check with the warm engine since the plugs were all out and got (starting with #1):

180-170-175-180-160-180

 

[Rich]

If your head gasket is good then I would guess the head is cracked and leaking coolant into an exhaust port.

 

[KliersLC]

Do we have a liquid cooled EGR system on the 80? Too cold and dark to go look, but some of the bigger rigs I have worked on had this.........
Other than that you have me stumped.
Good luck
Dan

 

[tarbe]

I hope your sample gets back to you from Blackstone quicker than mine from two weeks ago. I hate waiting 10 calendar days to find out if you have water/fuel/glycol in your oil.

Have you noticed your oil level either going up, or dropping at a much lower rate?

I'll have to check, but I can't imagine ours having a cooled EGR. More common on modern diesels for sure...that's where the increased soot loading in the oil is coming from.


Doug - you get my vote for most adventure-prone cruiserhead on the board!

 

[landtank]

Personally, I'd just go with the obvious.

 

[e9999]

put fluorescent dye in coolant to help find the leak if it's external?

 

[jonb96150]

If your head gasket is good then I would guess the head is cracked and leaking coolant into an exhaust port.

This would be my guess also. Where coolant passageway is closest to exhaust passageway. After you invent x-ray glasses to look into there can I borrow them?
Good luck

 

[skyshark186]

I chased a coolant leak around for a long time, and ended up a lot like you. Dont know if your is as easy as mine ended up being, but this is what I found. Also dont know if the same applies to a later 80 or not.

On mine, under the front of the driver side just outside the radiator is a large copper cylinder with two say....one inch lines running into it. I still dont know WHEN its leaking, but it only does it if the radiator is completely full. It leaves no residue below it, or on the hoses so it took a while to find. But that was my culprit, leaked quite a bit actually.

Good luck. Hopefully its not a cracked head.

 

[LEXUSBEN]

Doug, sounds like you definitely have an internal coolant leak (burning coolant). I worked on too many truck 3.0 v6 to count with blown head gaskets. So here is my 2 cents. First thing I would do is find a "Block Tester" you can usually get them at napa and I think they are about $40-50. It is a diagnostic tool ( ) that uses a blue liquid to determine if there is any exhaust gas in the cooling system. You put it in the radiator neck and draw air from the cooling system through the liquid, if it turns green - leaking, Yellow - massive leak (read radiator is now a muffler). Of all the methods I have seen over the years this seems to work the best.

One other way to do it is if you have a cooling system pressure tester, warm up the engine, pressurize the cooling system with the tester, pull spark plugs and look for steam emmiting out of the holes. The pressure tester will push coolant into the cylinder with the engine off, the engine temp will vaporize the coolant into steam.

The v6 engines used to bridge a coolant passage to the cylinder, no milky oil or other common blown head gasket symptoms. I know the 1fz engines I have done head gaskets on have pushed the sealing ring of #5 is pushed into the cylinder, usually causing a loss of compression and internal coolant leak.

As for your steam cleaning question, it takes longer than you think to completely clean the combustion chamber using coolant. My biggest caution on this is and don't let it scare you I just want you to know. I have seen several gaskets that were leaking bad enough and the people just kept driving. Well the hot spark plug was doused with coolant constantly and the porcelain around the electrode cracked, fell off into the cylinder and gouged the sh$$ out of the cylinder walls. I wouldn't believe it if I hadn't seen it myself. So keep this in mind.

If it's just starting to leak you won't notice much coolant loss during driving. Some but not a ton. the combustion pressure keeps the coolant in the radiator, it evaporates some. Once you shut the engine off the combustion pressure is now 0 and the cooling system is still about 12 psi, so the coolant is going to push into the cylinder and be burned out on next startup.

hope this helps, ben

 

[Beowulf]

Personally, I'd just go with the obvious.

Agreed. Sorry Doug, but it looks like a HG is in the near future for your '97. That's a real bummer.

-B-

 

[lovetoski]

I hope your sample gets back to you from Blackstone quicker than mine from two weeks ago. I hate waiting 10 calendar days to find out if you have water/fuel/glycol in your oil.

Blackstone usually turns their samples around in 2 days max, one day is more common. USPS however can take 2 weeks to get a sample to them if you use the cheapest postal method (forget what it is). I now pay a few bucks more and send it priority (2-3 day delivery) and get fast results. Conversation w/blackstone confirms I'm not the only one to find out how slow USPS can be.

 

[IdahoDoug]

Ben,

It cycled from hot as I prepared the truck for plug removal and subsequent compression test. No evidence of water on the perfectly level piston tops (which I could see). During the compression test, no evidence of coolant being misted out of any plug hole - I checked each and every time for the minutest drops with a bright flashlight and my nose. Nothing.

The coolant into the exhaust due to a head crack is what Dan and I discussed. Neither of us had heard of any such thing happening on this engine, but it's frankly still on the table.

Drove it to church today. On startup no steaming. Ditto driving. No 'catch' during the starter engagement indicating a hydrolocked or partly hydrolocked cylinder. Normal engine temps and the feel of a healthy IFZ engine at all times. We're heading out to go for a hike, so keeping the truck in operation at this point.

DougM

 

[MH_Stevens]

If you are now in Idaho, IdahoDoug then it should be cold enough to see steam on start-up if your losses are as big as you say. Try it on a dark cold night with a flashlight and check the crank case vent or the oil filler cap as well as the exhaust.

There are only THREE ways coolant can leave your engine. It can leak out, it can be vapourized out either via a piston or the oil vent, or it can be stolen (taken out). Are you sure you have not pissed-off your wife or neighbor who might be sneaking into your garage at night with the turkey baster?

 

[Rich]

As long as you are correct that coolant is getting into the exhaust, it seems to me that regardless of the cause your next step is to pull the head. Either the head is cracked, or the head gasket has failed. There are no other possibilities are there?

 

[IdahoDoug]

I'm with you guys. If coolant's in the exhaust I've got a problem. And believe me, I rechecked the forum list to see who in the area is playing an excellent practical joke on me, but nobody close enough - heh.

However, as you can see from my other thread "need someone to listen", I'm looking for elimination of what I thought was the CERTAINTY of water in the exhaust - that boiling sound. Might be a normal catalytic converter sound. Ironic that I have access to two other 80s - one in my garage and my bro in law's one street over - but they're both the older single cat style. Shouldn't take long to get a couple data points and I'll be able to confirm this. I've never heard of it. Need some young guys with good ears to hear this - you old guys need not apply - heh....OK, I'm 44 so in the latter group.

Regards,

DougM

 

[MH_Stevens]

Have you replaced or checked the seal on the radiator cap? Could be getting some evaporation from there. If that is OK then try this. Get the truck hot so coolant is under pressure, remove the spark plugs and have someone crank the engine while you watch the plug holes. If water is getting in there you should see some blow out. If test is negative, remove the exhaust manifold and do same holding a cold plate or sheet of metal over air flow that will condense any steam being emitted, and look for condensation.

In my experience, these crazy unexplained things are often the most basic and obvious things that just get overlooked. Get someone with a good nose to sniff for a leak.

 

[landtank]

I've been thinking about this all day and with the exception of the HG the only other place I can think of that could introduce coolant into the combustion chamber is the throttle body. The truck's TB has coolant passing through it to protect from icing and if there was some crack or something in there coolant might get sucked in. I have never heard of this happening but thought I'd post it.

 

[RavenTai]

Moisture in the exhaust system can be normal, water is one of the byproducts of combustion. In the winter mine makes clouds of steam wile warming up, sometimes even liquid water coming out of the tail pipe. Moisture in the exhaust in conjunction with coolant smell and coolant loss is the bad indication.

Rick is most likely correct here

But you are asking for possibilities so one possible path for coolant into the exhaust is through the "idle air control valve heater". As far as I can toll these coolant paths in the throttle body are directly cast in the aluminum, no seals to leak so the TB would have to be physically damaged (such as a crack, corrosion or manufacturing defect) for coolant to get out into the intake stream.

Could the coolant you are smelling wile at the back of the truck be from another source being blown to you by the wind? You say you have seeps, I would fix them up and see what your coolant loss is.

Have you done the bubble test yet? It requires no tooling and is fairly conclusive assuming the cooling system is known to be free from air when you start out.


Edit: too slow

 

[e9999]

I don't get this "boiling sound in the cat" thing.
The exhaust gases are way above boiling temperature. So are the cats.
How could water be boiling in the cats?
Long shot: you wouldn't have coolant dripping on your cats from the outside, somehow? some rear heater hose or something?
But then again, you say you could smell the coolant inside the exhaust....
E

 

[RavenTai]

Exhaust gasses and operating cats are both above the boiling temp but during warm up on a cold day water could still collect in the exhaust system including the cats until everything gets up to temp.