N/A Strange car problem

jsstevens

jsstevens

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jsstevens
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I've seen a lot of strange things cars do, but this one has me puzzled. My son has a 1995 Toyota Avalon with ~320K miles on it. The engine actually has ~280K miles. It was replaced sometime before my parents bought it. They (while keeping it well maintained) drive it up to 240K miles then sold it to my son. It's not been so well maintained since but he's learning...

Anyway, it had some overheating issues. We replaced the water pump (which needed it!). It did fine for a while, then started losing coolant somewhere. He'd top it off periodically (a couple of times a week). Then he noticed that if he added water to it he'd have to wait an hour or two before it would start. (It's not doing the cold idle thing very well at this point. Once it warms up it's fine.)

He replaced the radiator and the coolant leaks stopped but it would occasionally over heat in traffic. I told him he might have bubbles in the coolant system. (I had an mid 80's vintage Honda that had a know issue with bubbles once the coolant was drained and refilled.) So today, he was getting the bubbles out by running the car with the radiator (not reservoir) cap off and adding coolant as the bubbles came out. All went fine until he put the radiator cap on (with it running). It died. Immediately. So somehow, pressurizing the coolant system kills the engine. I've done some web searches as has he and I can't find a single reference to that.

Any ideas?
John
 
Any chocolate milkshake looking oil, or steam/coolant odor coming out the exhaust? Does one plug look different (clean or white) vs the others? Thinking head gasket leak.
 
Based on what's written, another vote for head gasket issues.

A quick look for engines shows many available for ~$400-$600 depending on where you are.
 
Head gasket was my suspicion with the intermittent overheating problem. And it's probably been hot enough. But the oil is clean. Haven't pulled the plugs, yet. But why would that cause it to die as soon as the radiator cap goes on?
 
AggieMike88 said:
Based on what's written, another vote for head gasket issues.

A quick look for engines shows many available for ~$400-$600 depending on where you are.
Click to expand...

He lives in Gainesville Fl. But the rest of the car is not in good enough shape to warrant the engine swap.
 
jsstevens said:
But the rest of the car is not in good enough shape to warrant the engine swap
Click to expand...
Sorta depends on viewpoint... If one can afford the replacement car and pay in full with cash... I agree with you. But if one cannot, then $1000-1200 for the engine plus install and you've got transportation for another year or two while saving up the cash for the replacement car.
 
AggieMike88 said:
Sorta depends on viewpoint... If one can afford the replacement car and pay in full with cash... I agree with you. But if one cannot, then $1000-1200 for the engine plus install and you've got transportation for another year or two while saving up the cash for the replacement car.
Click to expand...

Trust me when I say the engine is the strong part...
 
So I rechecked and the oil is clean. So what's next?
 
Can somebody explain the mechanism that would kill the engine as soon as the coolant system is pressurized? If we've got one or even two passages for coolant to get into the combustion chamber-assuming they don't pass coolant until pressurized-it'd run roughs all get out. But die?

John
 
How old is your son? (ie, who is going to pay for the replacement car?).
 
Matthew said:
Depending on where and what is getting past that gasket, different symptoms can occur.

http://www.agcoauto.com/content/news/p2_articleid/200

Multiple symptoms might even mean cracked heads or other damage.
Click to expand...

So I read the article at the link. I've seen all those symptoms in (different) cars over the years. This one doesn't seem to have any of them exactly. At this point, it doesn't appear to be losing coolant. The oil is clean. It may or may not intermittently overheat (but apparently never at highway speed). But when cold, it will die when the coolant system is pressurized.

John
 
JOhnH said:
How old is your son? (ie, who is going to pay for the replacement car?).
Click to expand...

22. He's going to have his hands full for a while, no doubt.
 
jsstevens said:
Can somebody explain the mechanism that would kill the engine as soon as the coolant system is pressurized? If we've got one or even two passages for coolant to get into the combustion chamber-assuming they don't pass coolant until pressurized-it'd run roughs all get out. But die?

John
Click to expand...
That one's got me wondering, too. Pressurizing that coolant must be pushing it somewhere it shouldn't be. Di you think those bubbles he's seeing in the radiator are from gasses being pushed into the coolant system or do you think it's more like trapped air from when he refilled it is being released?
 
Matthew said:
That one's got me wondering, too. Pressurizing that coolant must be pushing it somewhere it shouldn't be. Di you think those bubbles he's seeing in the radiator are from gasses being pushed into the coolant system or do you think it's more like trapped air from when he refilled it is being released?
Click to expand...

I believed it to be trapped air from when he drained and refilled. The one time I saw a cylinder to coolant jacket head gasket leak it wasn't subtle. As soon as the thermostat opened it shot a stream of coolant the diameter of the radiator fill neck straight up 5 feet with each compression stroke.
 
I've just exceeded my car problem diagnosis level of expertise. This is where I usually call my brother the mechanic.
 
head gasket, or head crack doesnt always make the oil milky.
Ive had a few on cars/bikes over the years. If it heats up and wont start, its the head/gasket. had a ****ty dodge something form the early 90's do that on me in college.

Scrap it and find another.
 
jsstevens said:
So I rechecked and the oil is clean. So what's next?
Click to expand...

Check spark plugs to see if one or two has been steamed clean.

Check exhaust for steam and or droplets of water, which may be difficult since most cars have water droplets come out the exhaust.

Lift front of car 4 or 6 inches, run without cap, look for more air.

If all else fails.... Quando omni flunkus, moritati
 
Well, it sure does sound like a broken coolant jacket to me, too. BUT, it's not necessarily the head gasket, though I'd go there first as well. Some Toyota engines have coolant-heated throttle bodies. It could be getting in the engine from there. Maybe the intake manifold gasket on a V6 (probably not a 4banger, though).

Another way pressurization could affect the engine running is if there really isn't enough coolant in the system. Putting the cap on can trap a bubble, that could otherwise get out. The engine could get killed by excessive cylinder temperature, or by exposing the coolant temperature sensor so the PCM thinks the engine is cold when it isn't. This is a very common error if the engine isn't warmed up until the thermostat opens before replacing the radiator cap. Especially if the thermostat isn't installed correctly (some have a small vent to prevent just this occurrence -- it has to be installed at the top of the thermostat). Some vehicles -- including some Toyotas -- also have a heater valve that has to be opened during the bleeding operation. Without that, the heater core will be full of air.

A change in temperature due to the cooling system being closed could cause all sorts of leaks, including vacuum leaks (which will kill an engine very easily). Or maybe a coolant leak is getting coolant on critical electronics.

Coolant will also permanently ruin oxygen sensors; this can cause persistent poor driveability, even after the leak is repaired.

Are you SURE it's not losing coolant? Sometimes, pressurized oil or transmission fluid can be pumped into the radiator, through the block or the transmission cooler, respectively. If you start the engine and run it for a minute (no longer is necessary) with the cooling system closed, is the upper radiator hose firm to the touch? This is a very quick'n'dirty coolant leak test. It doesn't have to warm up fully, but it does have to try to pressurize. Does the heater work?

If the engine is burning coolant, it will make persistent white smoke. The exhaust will have a sweet smell (unlike the common cold-weather combustion water). A MILD head gasket breach will not make the oil look too bad, but it may form snot-like substance on the inside of the oil cap. That's condensed steam. It may not get any coolant in the oil at all if the breach is between two cylinders. Especially on a V6, where oil doesn't have to go through the heads to lubricate the valvetrain.

I think you would be best served by an hour of professional diagnosis. This is stuff a good mechanic with physical access to the vehicle can figure out pretty quickly. It's not easy to do over the Internet.
 
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What I would do to trouble shoot is run some compressed air into each cylinder and listen or look for bubbles in the radiator. You can narrow it down to a cylinder or eliminate the cylinders all together if you don't get bubbles.
 
When my car blew a head gasket, it was the coolant that started getting very dirty. It looked like there was sludge in the overflow tank.
 
jsstevens said:
Trust me when I say the engine is the strong part...
Click to expand...

Depending on your son's (and your) situation, this may not be worth saving, then.

I bought a whole new-to-me BMW for $2000. In pretty good shape, no less. A lot of miles, though.

Grum.Man said:
What I would do to trouble shoot is run some compressed air into each cylinder and listen or look for bubbles in the radiator. You can narrow it down to a cylinder or eliminate the cylinders all together if you don't get bubbles.
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You bet. This works nicely if there is compressed air available. But, that's not too common for a shade tree mechanic. For the OP, if you do have compressed air and a spark plug adapter (they aren't expensive), do this at TDC on the compression stroke, and pressurize to 100 PSI. While you're at it, listen at the throttle body and exhaust pipe for hissing, as that checks the valves.
 
MAKG1 said:
Well, it sure does sound like a broken coolant jacket to me, too. BUT, it's not necessarily the head gasket, though I'd go there first as well. Some Toyota engines have coolant-heated throttle bodies. It could be getting in the engine from there. Maybe the intake manifold gasket on a V6 (probably not a 4banger, though).

Another way pressurization could affect the engine running is if there really isn't enough coolant in the system. Putting the cap on can trap a bubble, that could otherwise get out. The engine could get killed by excessive cylinder temperature, or by exposing the coolant temperature sensor so the PCM thinks the engine is cold when it isn't. This is a very common error if the engine isn't warmed up until the thermostat opens before replacing the radiator cap. Especially if the thermostat isn't installed correctly (some have a small vent to prevent just this occurrence -- it has to be installed at the top of the thermostat). Some vehicles -- including some Toyotas -- also have a heater valve that has to be opened during the bleeding operation. Without that, the heater core will be full of air.

A change in temperature due to the cooling system being closed could cause all sorts of leaks, including vacuum leaks (which will kill an engine very easily). Or maybe a coolant leak is getting coolant on critical electronics.

Coolant will also permanently ruin oxygen sensors; this can cause persistent poor driveability, even after the leak is repaired.

Are you SURE it's not losing coolant? Sometimes, pressurized oil or transmission fluid can be pumped into the radiator, through the block or the transmission cooler, respectively. If you start the engine and run it for a minute (no longer is necessary) with the cooling system closed, is the upper radiator hose firm to the touch? This is a very quick'n'dirty coolant leak test. It doesn't have to warm up fully, but it does have to try to pressurize. Does the heater work?

If the engine is burning coolant, it will make persistent white smoke. The exhaust will have a sweet smell (unlike the common cold-weather combustion water). A MILD head gasket breach will not make the oil look too bad, but it may form snot-like substance on the inside of the oil cap. That's condensed steam. It may not get any coolant in the oil at all if the breach is between two cylinders. Especially on a V6, where oil doesn't have to go through the heads to lubricate the valvetrain.

I think you would be best served by an hour of professional diagnosis. This is stuff a good mechanic with physical access to the vehicle can figure out pretty quickly. It's not easy to do over the Internet.
Click to expand...

+1. If the coolant were getting into the combustion chamber you'd see/smell it. This sounds like a sensor problem, and that's going to be hard to diagnose remotely.

Cars do have a finite life, this one sounds like it has reached it.
 
I was going to suggest changing out the thermostat and getting a new radiator cap to ensure there's no problem with the cooling system itself. Installing the thermostat backwards is a common problem with overheating issues after work on the cooling system has been done. Next, I'd be using a multimeter to test the coolant temp sensor/clean connections, or just puting in a new one, to make sure the ECU is getting proper signal.
 
FormerHangie said:
+1. If the coolant were getting into the combustion chamber you'd see/smell it. This sounds like a sensor problem, and that's going to be hard to diagnose remotely.

Cars do have a finite life, this one sounds like it has reached it.
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It doesn't owe him anything, that's for sure.

I'm suspicious of a sensor problem because it dies so fast. It's almost as if someone switched it off. That's why none of the other failure modes make sense to me yet. But obviously, I've still got things to learn...
 
Pull and inspect plugs.

You may have a leak that is intermittent and shows only under coolant system pressure (cap on/off behavior).

The fuller the coolant system, the quicker the behavior, cuz pressure builds instantly (small headspace); if the system is less full, more headspace, takes more time to build pressure (plus, fluid level may be below leak when less full).
 
Sell that **** to Pick A Part and buy another slug off Craigslist.....


There.....I said it. :cool:
 
jsstevens said:
Can somebody explain the mechanism that would kill the engine as soon as the coolant system is pressurized? If we've got one or even two passages for coolant to get into the combustion chamber-assuming they don't pass coolant until pressurized-it'd run roughs all get out. But die?

John
Click to expand...
I had a car long ago that would run rough on hard acceleration. Threw me for a loop until I found a small crack in the radiator hose that ran across in front of the
distributor. When the cooling system pressured up, the crack would open and spray the distributor with coolant. Never did kill the engine, though. You could have
a similar leak spraying the ignition in the Toyota.

In another car I had an intermittent misfire that I struggled with for quite awhile. Finally I found a cracked insulator on the business end of one of the plugs. I thought
replacing the plug would fix it - and it did - for awhile. What was causing that was a small head gasket leak, spraying the plug with coolant. The car had had a leaky
water pump for quite awhile. When I got around to fixing that, the increased cooling system pressure caused a major hemmorhage into that cylinder -which turned
into hydrostatic lock. Junkyard time! No regrets - I certainly got my money's worth out of that car (bought it new, drove it for 19 years).

Dave
 
Unit74 said:
Sell that **** to Pick A Part and buy another slug off Craigslist.....


There.....I said it. :cool:
Click to expand...

That's what you do when they're that old. I see all sorts of running vehicles in the $2000-$3000 range on CL and the new Facebook sales thing.

Stuff that someone who thinks they "deserve" a $20,000 vehicle and a car loan wouldn't touch, but plenty comfortable and rolling if not stylish in any way.

Judging by most of the ads around here, the whole deal would go down easier if whoever went to negotiate spoke Spanish. I let a cheap and running plow truck get away, by not watching for a while. Oops.

Se Habla Español. Sí.
 
Does it die right after you put on the cap? Or take a few minutes after cap installation?
 
Is the cap in good shape? It should regulate to something like 16 psi, I think. I don't know if that would make such a difference. Is the engine hot or cold? I wonder if the thermostat is also playing some kind of role?
 
Although I've never heard of such a thing, does Toyota have a pressure sensor somewhere in the cooling loop? I'm just trying to think of what would stop the engine immediately after putting the cap on.

Edit: The only other guess is it messes with the coolant temp sensor somehow?
 
Bill Jennings said:
Although I've never heard of such a thing, does Toyota have a pressure sensor somewhere in the cooling loop? I'm just trying to think of what would stop the engine immediately after putting the cap on.

Edit: The only other guess is it messes with the coolant temp sensor somehow?
Click to expand...

That would fit the symptoms. I'm researching... It's the ubiquitous Toyota 3.0 V6 from the 90's. It has sure been bullet proof until now...
 
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