Coolant level dropping, but not showing on pressure test?

Hi all. I've had my 85 Van in and out of the shop several times in the last few months because of overheating issues. I ended up going on vacation for 2 weeks and left my van sitting the whole time. Came back and everything started fine, but seemed to run a little on the hotter side (nothing severe at this point), however as I kept driving it, it would overheat as soon as I got off the highway to my work. I brought it to my mechanic who has rebuilt the engine on this Van and done quite a bit of other work on it, and he suggested getting the radiator cleaned out and thermostat replaced. He said bottom (output) hose out of radiator was cool, so there was no circulation of fluid. He also replaced my radiator cap. So all of that was done and I took my van out, and next day it was overheating again. By the time I got it to work, there was coolant dripping very heavily from what looked like part of the frame in front and underneath the radiator on the driver's side. I filled the filler with water after it cooled and drove it back to the mechanic only a few miles away. He said he thinks one of the hoses just under the filler cap wasn't tightened enough, so he tightened it and refilled with coolant. He did a pressure test on it twice and said no drop in pressure. I picked it up and drove it for about two weeks, no problems. Then one day out of the blue, it just decided to overheat again on the way to work, just getting off the highway. I waited until it cooled and filled it back with water that night and drove it home. It lasted about 3 days until it overheated again. Waiting to cool again and filled it with water, only this time it didn't even last a whole day. The next day on the way to work, it was overheating again and I pulled it into a parking lot as soon as I got off the highway and inspected around a bit under the seat. It almost seems like the coolant is coming out of the reservoir overflow. It definitely is not leaking from the reservoir level sensor. I have actually replaced the sensor and gasket/grommit fairly recently with a brand new one and there is no sign of leakage through that. But I am thinking that the coolant coming from the overfill is leaking out and running down the frame and dripping from where I saw it leaking originally. At this point, I was so fed up, I just called AAA and had it towed back to my mechanic. Now it is in the shop again, he's doing pressure test on it and still can't find any leaks. Are we missing something here? I am getting super desperate to figure out what's going on and he can't seem to find the problem either. Is it possible that the system and actually push out too much coolant out of the coolant overflow so that it doesn't even have enough left to cool it? Each time it overheated, you could hear a strong bubbling sound coming from the reservoir tank as if the liquid was boiling. Could too much pressure by building to force it to act in a different way? I'm all out of ideas and I've checked a around on other threads here and nothing seems to address it very specifically.

Has your mechanic tested for exhaust gasses in the coolant? A headgasket breach is one possible cause (and not at all unlikely if an aftermarket headgasket was used for the rebuild).

Although a significant leak in the cooling system is also a possible cause, that much lost coolant should have been easy to find (generally if not specifically) without pressure testing. That being said, a lot of mechanics miss leaks from the "hose of death" at the rear of the head (leaks onto the tranny and the blows rearward at highway speeds). Still, I'm most suspicious of the headgasket.

Gwen

If it turns out that your radiator is plugged-up, don't waste your time on a re-core.
Get a new one or have Ability Radiator in Yuba City, CA build you a 3 row high efficiency rad.
When I bought my van I took it to a shop who sent the rad to another outfit to be re-cored. Turned out that their "re-core job" was a total farce. It was really no better than it was before.

If your radiator is compromised in ANY way, it's just a matter of time before your van will be useless.

http://www.toyotavantech.com/forum/s...ator+Yuba+City

:whs:

That's my experience as well — "flushing" or "rodding out" the rad is buying a little time at best, throwing money away more often than not. The high-efficiency recore is money well-spent. :thmbup:

BUT I still recommend checking for exhaust gasses in the coolant, if for no other reason than repeating overheatings can lead to HG damage where none was before ...

Gwen

Thanks for the insight. I wish I had known about the recore earlier. Radiator was already pulled, flushed and reinstalled. And I am running low on cash. I will mention to my mechanic to check for emission gasses in the coolant, but I believe he said that if it was leaking around gaskets, the van would be running quite a bit different - especially leaking at a rate of being full one day, and low enough to overheat the next day. And that's all within only 20 miles of driving. Seems something would be running significantly different with that amount of internal bleeding.

So things are progressing pretty slow with diagnosing the coolant leak. My mechanic tried the pressure test overnight, and it did loose all it's pressure. He suspects that I need a new filler housing? He explained it as the part that the actual filler neck is part of, where multiple hoses come from and the temperature sensor also is located. He said that a loss of pressure in this can cause the pressure valve in the radiator cap to not move properly and so I am losing a huge amount of coolant through the reservoir and overflow. Just to get a second opinion from anyone who has the insight, does this sound possible or even probable that this would happen? I've owned this van for 2 and a half years now, but still very novice about many of the systems on this van. The cooling system has been the biggest frustration, so any help or advice would be greatly appreciated.

Okay, so I've been doing a lot of hard thinking about the overheating problem I have and I've come up with a theory and I want to run it by you and ask your opinion on whether you think this is a solid theory or if you think there could be another cause.

So I got my van back from my mechanic for the 4th time. This time he replaced my radiator cap housing. The old one looked pretty decrepit inside and out and he said it could have interfered with the way the valve on the cap was reacting. So now I have a flushed radiator, a new thermostat and new radiator cap housing. My mechanic said he left my van running for 2 hours and it ran fine with no overheating. I pick it up, drive it to work (3 mi) and then back home (14 mi), then drive it back to work again, and you gotta be roflroflroflrofltin' me. I get off the highway and it's working its way fast past the middle line and I get on the back roads and it's moving up fast and by the time I get to work (about 1.5 miles off the highway), it's in the red. Now I'm feeling more and more hopeless like there is some really thick wall between me and figuring out this problem. :pissed::wall:

However, all day I've been carefully thinking this through. I waited for my engine to cool, filled it back up with water. This time, it took more than ever - about 60 oz of water. I started it up and let it run for 20 minutes with the gas pedal depressed about 1/3 of the way, and it ran perfect. Needle was only a third the way up the temp gauge. So I thought, well roflroflroflrofl, I might as well just drive it home, I think I can make it and heck, maybe my mechanic didn't put enough coolant in it. This time I watched that needle like a hawk. Thinking about everything going on under my seat. Radiator filler is full, reservoir is empty as the orange radiator light is on. The first half of the ride is mostly down hill going from my work in Kearny Mesa San Diego down into Mission Valley on highway 15. Needle has not moved yet. Then once I cross Mission Valley it's a climb to get up into the city heights area. Halfway up the climb I notice needle moves up, but only a bit, now it's just below half and the orange radiator light has gone off, telling me that the pressure has built to the point where coolant is now filling the reservoir. I still have another 7 miles to go, but not too many intense hills. As I near my exit, the needle keeps climbing and is now barely over half way. Then once I'm off the exit and slowing down, the needle just skyrockets and within only about 2000 feet off the exit, it's just about in the red. Lucky I only live about 2000 feet from the exit, and I was lucky enough to pull into my spot and further inspect the situation. I lifted the seat and sure enough the reservoir had overflowed and was dripping on numerous components - mostly suspension parts like the drivers side control arm and stabilizer bar and whatnot - they're all dripping like they just got out of the shower or something and eventually dripping on the ground. Listening to the reservoir I can hear a very clear and prominent bubbling sound. I pull the reservoir cap off and the tube out and notice there is no liquid coming from the tube, but as I drop the tube into the coolant in the reservoir, bubbles are generously flowing out meaning it is in the form of a gas of some sort.

So here's what I'm wondering. Could it be that the only way that bubbles could be coming out of this is if a gas was being forced into the system somewhere from within the engine block? After all, if the system is supposed to work by filling the reservoir with expanded fluid, you would think all the lines would be just that - fluid! So how could it be that there is a gas or air bubbling into the reservoir tank? Something is causing the system to pressurize to the point where it's overflowing way too much coolant to the point where it's running out and very quickly overheating. And this is after a completely full filler and only 14 miles of driving. I don't see a leak anywhere else, and my mechanic has done numerous pressure tests on this. As Llamavan has suggested, I am tempted to think maybe it is the radiator and the flush really didn't do much and it needs a re-core. I would be happy to spend the money on that, but I don't want to spend any more money without actually fixing the problem, I am going broke over this and I have to start being very strategic with how I approach this problem. So what I am wondering is does this sound like definitely an emission leak into the coolant system or is there hope that it is something else. My van sounds like it's running fine and my mechanic didn't think there was a breach anywhere, but I'm totally wrecking my brain trying to figure out if it's not an emission leak, could that only leave a poorly functioning radiator left as a possible culprit?

Any and all advice would be so much appreciated. Sorry this is so long, but I just wanted to be as thorough with my explanation as possible in hopes that someone out there has a clear answer on this. Help me Toyotavantech members, you're my only hope! :dizzy:

As I understand it, the overflow reservoir should always have coolant in it... just different levels for cold vs hot. That said, the larger issue sounds like a bad head gasket to me. I had the same issue with my van when I bought it. You could let it idle and even drive it for a while, but once you really got going down the road it forced enough of the coolant out of the system, to where it would quickly overheat. What was left of the coolant was bubbling and roiling. Maybe others can speak from experience, as far as what these engines can handle, but if you're hitting red on the temp gauge and can hear bubbling/boiling I'd guess you've probably blown it by now even if it wasn't the original issue. With the engine cold and full of coolant/water, I was able to start the engine idling and remove the coolant cap, give the engine gas and see bubbles rise in correlation. To further confirm, my mechanic did a compression test and found the cylinder where the head gasket had blown.

I second everything Roger said. I'll relate my headgasket story for you. When my headgasket went it started with a bad pressure cap seal that caused overheating two or three times until I realized there was some debris in my coolant that damaged the cap seal so it wouldn't hold pressure. The debris looked like stones that I suspect was calcification from lack of maintenance by the previous owner and also owing to the fact I had left it sitting for four years following an accident. After I replaced the cap with my favorite Stant lev-r-vent I still had the same problem. After several more overheat cycles, mostly like you after getting off the freeway, while trying to diagnose it, the headgasket let me know once and for all it was done and dumped the coolant in the oil and the oil in the coolant. After repairing everything it did it again on the first test drive and I immediately went back to the replacement radiator cap. Testing revealed it had a faulty seal that upon closer inspection had a tear around the vent lever stem that appeared to have been during manufacturing. I put a new Toyota cap on for good measure and the problem has been solved now for 4 years. I still kick myself for not going back to the pressure cap sooner as the symptoms suggested that but I kept telling my self,"No way, it's brand new".
It sounds to me as if you have a leak between a cylinder and a water port and as combustion pressures increase at higher engine speeds the pressure in the cooling system is venting out all your water. Your not overheating on the highway due to the air flowing over the engine helping to cool it and the higher efficiency of the radiator at those speeds. I suspect if you tried to drive farther on the highway, as more of the coolant was vented you would overheat at highway speed. A compression test will usually but not always show the suspect cylinder but at this point I think a good combustion gas test of the coolant will confirm a bad headgasket. Hope it's not for you wallet's sake but it sure sounds like it.

:whs:

Gwen

My van had similar symptoms. After getting screwed by incompetent/greedy shops, I ended-up waiting almost a year for a mechanic friend to recover from an on the job shoulder injury. Once he was ready to work on my van I told him to fix anything and everything he thought it needed.
We already knew that the rad was bad, the exhaust manifold was leaking, there were broken sensors and old hoses. He discovered that the hose of death engine plate had tons of tiny pin holes in it (corrosion). He figured that the coolant was slowly oozing out the pinholes then evaporating on the hot engine.

So we got the Yuba City 3 row high efficiency rad, 2 electric cooling fans with programmable on/off temp sensors, new exhaust manifold, had to have the hose of death engine plate outlet thing custom made, new hose of death, new sensors (BVSV, VSV's), checked the fuel injectors, new Toyota OEM head gasket kit, and OEM thermostat. It was a big job but it was worth it.
Now my van runs perfect. All in all I spent nearly 3 years trying to figure out all the problems and finally get them fixed. The hard lesson I learned was going cheap on parts and using unknown/suspect mechanics was just a quick way to become frustrated and broke.

Also I have to mention that my mechanic was referencing this website and was in email contact with Timsrv for advice. Thanks again to Tim and everyone else here for all the great info and support!:thmbup:

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I had a few more thoughts on this. Let me start by saying I am in no way knocking your mechanics ability but... you did mention he rebuilt the engine for you and while I know people WILLING to admit mistakes I don't know anyone who LIKES it. Throw in the fact that there is potentially money involved it's possible your mechanic is just as hopeful as you that it's not the head gasket and willing to look into any other possibility first. Unfortunately at your expense. Two other questions come to mind after re-reading your previous posts. Did he use a genuine Toyota head gasket and did he use a genuine Toyota thermostat. I know these two subjects have been beat to death on the forum but even I recently considered an aftermarket t-stat so I wouldn't have to wait for it to be ordered in. I eventually thought better of that notion. Again, I'm in no way passing judgement on your mechanics abilities just throwing out some thoughts that crossed my mind I felt may be of value.

My mechanic has been the best mechanic I have ever dealt with. He has never given me a reason not to trust him. He is quite old, but a master mechanic from Vietnam and specialized in older Asian makes and models. He actually seemed to know this van quite well when I first brought it to him. He always says that he will use Toyota brand parts when he can. The rebuild was 2 and a half years ago, so I don't remember 100%, but I am pretty sure he said all seals and gaskets were Toyota parts. He is a very good mechanic and he works slow, but one thing is he has never seemed to cheap out on parts for me. He has also been able to diagnose almost all the problems with this van since I got it just by describing symptoms over the phone. He is a trusted mechanic and friend. However, he is getting up there in age, and experiencing some health issues. You did mention that he probably does not want to have to replace the head gasket, and I don't blame him.

Today after I explained everything to him that I noticed the other night (which I posted previously in my long detailed post), he said the head gasket is still his last suspicion of the problem, and maybe the dread of getting back into that had something to do with that, BUT he did ask if I could start the van and let it sit for a while until it got back up to temp. So I filled the radiator filler back up with water and let it sit in the driveway until it got to its normal temp (about 1/3 on the gauge) and then he said to shut it off and feel the radiator all around in different spots. So I crawled underneath and felt the radiator, and sure enough, the top of the radiator was very hot and the bottom was only mildly warm to almost room temp. He concluded that the person who flushed it probably did not do a good job and because of the inconsistent temperature, he strongly feels it is the radiator that is the culprit. But here's my thing, what about the bubbles in the reservoir? My mechanic did have a good point and it seems after all the work to fix the radiator, it is still the most probable issue, but can it explain why the system is pushing that much fluid into my reservoir and then when I inspect it after a drive, it is bubbling air? I'm still confused how anything but fluid could be in the system if I completely top it off. It wouldn't be sucking air back into the system from the reservoir because it starts off cold with a top off and only heats up and expands from there. So now I'm a bit worried that I may have two issues on my hands (although its just a worry and admit it's probably illogical and not likely). At least he was able to show me that the radiator is still not properly circulating coolant. I just want to be careful that I don't end up replacing that and then still not fixing the problem. If I have to replace or re-core the radiator and then find out after it's the head gasket, I'm gonna be in trouble financially. So should I go ahead and further seek out solutions for the radiator?

If you replace the head gasket and still have a clogged radiator :?:

Have you started it with the rad cap off and cold?
Shouldn't be bubbling out the gases you described

I have a similar problem in my 89. seems to loose coolant after filling up reservoir. it only seems to loose enough to turn on the radiator light. it hasnt over heated at all and it seems to stay at a consistent temp, it just doesnt want to hold that extra pint or so. Very strange.
Also wondering about the pin holes in the HOD cover. my 87 is apart for a new head gasket and the cover id definitely pitted. it seemed to hold air pressure but Im a little leary. Treselhed, is the cover you got available. I figure I should replace it while Im in there.
As always thanks for all your efforts@ TVT

Chardog1971 wrote:

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Treselhed, is the cover you got available. I figure I should replace it while Im in there.

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I believe that the 2WD and 4wd coolant outlet plates are different. The 4WD plate was N/A when I needed it, but the 2WD version was still available. If you use the search function you might be able to find the part #'s. My mechanic took my old outlet plate to a machininst who used it as a template to custom make a new one out of aluminum.

Good luck!