Coolant smell, no leaks found.

[LeeMajors]

I've noticed small whiffs of what I think is burning coolant with my driver's side window open, and engine warmed to operating temperature.

There is no change in coolant levels. Radiator is full, reservoir is full. I don't see any leaks below water pump. Checked the radiator hoses, and they seem pliable with no cracks noted. Checked lines running to the three way valve for the heater core, and noted nothing that looked like a leak. Checked the lines running to rear heater core with no leaks noted.

Now, I do have a vent that blows cold air while all the others blow hot air. Not sure if it's related.

It is inconsistent and doesn't happen all the time. I don't think it's coming from exhaust bc I smell it at speed from the front. Plus, I have no white smoke from tailpipe and it just smells like normal exhaust.

I'm kind of at a loss here. My suspicion is maybe a leaking heater core in the dash? Wouldn't I notice a coolant level change at some point?

Any thoughts? Burping reservoir lid?

 

[JayRolla]

I've noticed small whiffs of what I think is burning coolant with my driver's side window open, and engine warmed to operating temperature.

There is no change in coolant levels. Radiator is full, reservoir is full. I don't see any leaks below water pump. Checked the radiator hoses, and they seem pliable with no cracks noted. Checked lines running to the three way valve for the heater core, and noted nothing that looked like a leak. Checked the lines running to rear heater core with no leaks noted.

Now, I do have a vent that blows cold air while all the others blow hot air. Not sure if it's related.

It is inconsistent and doesn't happen all the time. I don't think it's coming from exhaust bc I smell it at speed from the front. Plus, I have no white smoke from tailpipe and it just smells like normal exhaust.

I'm kind of at a loss here. My suspicion is maybe a leaking heater core in the dash? Wouldn't I notice a coolant level change at some point?

Any thoughts? Burping reservoir lid?

This is kind of normal on these motors. Hint of coolant when firing up, small hints here and there at the light. Old school toyota guys will mention it. Some say its a headgasket issue but no water in oil and no smoke from tailpipe here either. I have thought maybe it comes from the overflow tank, which vents to the atmosphere, but I would not worry too much if not losing coolant.

 

[gamefreakgc]

This is kind of normal on these motors. Hint of coolant when firing up, small hints here and there at the light. Old school toyota guys will mention it. Some say its a headgasket issue but no water in oil and no smoke from tailpipe here either. I have thought maybe it comes from the overflow tank, which vents to the atmosphere, but I would not work too much if not losing coolant.

I thought the exact same thing when I first got my 4Runner. Coming from the 3VZ-E crowd where head gasket failures happen all the time, I was really worried after I had it for a few days. After working on the engine and getting used to the vehicle, there's actually nothing wrong with it.

We just get a nice benefit of sweet smelling exhaust gas! It's kind of like an old Italian guy, it leaves behind an aroma of cologne as it passes by.

 

[LeeMajors]

This is kind of normal on these motors. Hint of coolant when firing up, small hints here and there at the light. Old school toyota guys will mention it. Some say its a headgasket issue but no water in oil and no smoke from tailpipe here either. I have thought maybe it comes from the overflow tank, which vents to the atmosphere, but I would not worry too much if not losing coolant.

Yeah, that seems to make sense--but I've never had another vehicle do this. Even ones this old.

My big fear is headgasket of course, but it runs fine--no overheating, smoke or otherwise.

Lots of vapor in the mornings (super high humidity and cold), but it doesn't blow any when it warms up or when it isn't humid outside.

Plus, with a blown HG I would expect a coolant loss of some sort. I'm just kind of perplexed.

I'm a little gun-shy for HG stuff bc I lost a 97 Camry at 240k and an 85 MR2 at 190k to them.

 

[JayRolla]

Yeah, that seems to make sense--but I've never had another vehicle do this. Even ones this old.

My big fear is headgasket of course, but it runs fine--no overheating, smoke or otherwise.

Lots of vapor in the mornings (super high humidity and cold), but it doesn't blow any when it warms up or when it isn't humid outside.

Plus, with a blown HG I would expect a coolant loss of some sort. I'm just kind of perplexed.

I'm a little gun-shy for HG stuff bc I lost a 97 Camry at 240k and an 85 MR2 at 190k to them.

Just so you know its really hard talking to a guy with that pic as his avatar. LOL

Anyways I would not worry too much. You could get a compression/leakdown test for piece of mind.

 

[shootmymime]

do you use coolant?

i would smell it sometimes and turns out my water pump was leaking. got it all fixed and done.

 

[LeeMajors]

do you use coolant?

i would smell it sometimes and turns out my water pump was leaking. got it all fixed and done.

If it does, it's not an appreciable amount. Level has remained unchanged for the past month and a half, over 2500mi. Both in radiator and overflow reservoir.

 

[acr_ted]

I've noticed the same thing here as well - sometimes a whiff of hot coolant after shutting down and walking around the front. Like LeeMajors (!) said, I have not lost any coolant at all from the overflow bottle, and no coolant in the oil. Must just be one of those things. But of course I'll keep an eye on it just in case.

Ted

 

[jeremyc74]

How long has it been since the last timing belt/water pump service? It could just be loosing a little through the weep hole on the water pump. If you're coming due for a timing belt that might be a sign to go ahead and get it done.

 

[LeeMajors]

How long has it been since the last timing belt/water pump service? It could just be loosing a little through the weep hole on the water pump. If you're coming due for a timing belt that might be a sign to go ahead and get it done.

Unknown. No sticker on the timing belt cover. I'm assuming it's all original.

I had that thought as well.

 

[LeeMajors]

Ok guys, hate to dredge this back up again--but I tried to isolate the smell today with no luck. I was getting some stuff out of the truck when I noticed it in passing while it wasn't running.

Ok, no big deal--I set off trying to isolate it. Nothing from the engine bay, nothing from under the truck, near the exhaust or anything. The only place I smelled it was in the vents.

Now, it doesn't make much sense to be coolant if it's in the vents. It certainly shouldn't be burning there, and certainly not when the truck isn't running, right?

Any thoughts on what else it could be? Its a passing sweet, weird smell. It's kind of driving me crazy. I was sure it was burning coolant, but now I'm not so sure.

 

[JayRolla]

Ok guys, hate to dredge this back up again--but I tried to isolate the smell today with no luck. I was getting some stuff out of the truck when I noticed it in passing while it wasn't running.

Ok, no big deal--I set off trying to isolate it. Nothing from the engine bay, nothing from under the truck, near the exhaust or anything. The only place I smelled it was in the vents.

Now, it doesn't make much sense to be coolant if it's in the vents. It certainly shouldn't be burning there, and certainly not when the truck isn't running, right?

Any thoughts on what else it could be? Its a passing sweet, weird smell. It's kind of driving me crazy. I was sure it was burning coolant, but now I'm not so sure.

Well the heater core has coolant running through it and if there are some small pinhole leaks you would smell it in the vents. But again if you are pulling air from outside for the vents then it could be coming from the motor.

 

[LeeMajors]

Well the heater core has coolant running through it and if there are some small pinhole leaks you would smell it in the vents. But again if you are pulling air from outside for the vents then it could be coming from the motor.

That's the thing--it doesn't smell like the unburned coolant in the reservoir or radiator. It smells kind of sweet, so I assumed it was a passing whiff of burning coolant.

Now, I don't know what the hell to think. Guess it'll remain a mystery.

 

[BlazeRunner]

The coolant bypass hose is a somewhat common leak with age, and it's in a real tough place to diagnose. You can look for a leak behind the motor between the firewall where a plate stamped with an X is, under the heater hoses. You will only see coolant coming out from under that plate if it's leaked bad enough to fill the block valley under the intake manifold. I just replaced mine, it leaked and filled the valley and poured out back over the tranny bell housing once it finally went. I had a coolant smell for a while before it just broke loose altogether. The repair was actually quite easy, just slightly time consuming. All my intake plenum and manifold gaskets were toast anyway so it was a plus replacing all of those as well.

 

[LeeMajors]

The coolant bypass hose is a somewhat common leak with age, and it's in a real tough place to diagnose. You can look for a leak behind the motor between the firewall where a plate stamped with an X is, under the heater hoses. You will only see coolant coming out from under that plate if it's leaked bad enough to fill the block valley under the intake manifold. I just replaced mine, it leaked and filled the valley and poured out back over the tranny bell housing once it finally went. I had a coolant smell for a while before it just broke loose altogether. The repair was actually quite easy, just slightly time consuming. All my intake plenum and manifold gaskets were toast anyway so it was a plus replacing all of those as well.

How did you repair? Was it just a leak in the hose, or where it connects to the bypass valve?

 

[JayRolla]

That's the thing--it doesn't smell like the unburned coolant in the reservoir or radiator. It smells kind of sweet, so I assumed it was a passing whiff of burning coolant.

Now, I don't know what the hell to think. Guess it'll remain a mystery.

Hmm, i always thought all coolant smells sweet. Unburnt or burnt. Never heard someone say its smells different. When its on the ground its sweet, when it leaks it sweet, when you taste it its sweet. LOL. When you smell in in overflow or radiator it never smells the same as when leaking or in bottle.

 

[BlazeRunner]

How did you repair? Was it just a leak in the hose, or where it connects to the bypass valve?

The pipe itself seems to be made of steel, and was leaking at the flange where it connects to the block. That connection is at the very front of the motor though, under the manifold. Replacing the pipe wasn't necessary, but mine had corrosion and I felt it was the best thing to do in my case.
This is not my image, but it shows the hose very clearly.

 

[LeeMajors]

Hmm, i always thought all coolant smells sweet. Unburnt or burnt. Never heard someone say its smells different. When its on the ground its sweet, when it leaks it sweet, when you taste it its sweet. LOL. When you smell in in overflow or radiator it never smells the same as when leaking or in bottle.

Mine doesn't really smell sweet in the reservoir and radiator.

I've never definitively smelled burned coolant so maybe my radar is way off.

 

[LeeMajors]

The pipe itself seems to be made of steel, and was leaking at the flange where it connects to the block. That connection is at the very front of the motor though, under the manifold. Replacing the pipe wasn't necessary, but mine had corrosion and I felt it was the best thing to do in my case.
This is not my image, but it shows the hose very clearly.

I'll give it a look when I do the valve covers next week. I've got a leaky camshaft plug too, so I'm doing gaskets, plugs, and plenum gaskets. I'll get a good look in there when I do.

Thanks for all the info.

 

[BlazeRunner]

I forgot to mention the hose is sealed with a small amount of FIPG. There's not really a way to tell if there's a small leak in there without pulling the manifold off, or just wait till it gets worse like in my case.