Can anyone help me find out what happened here?

[davidavidd]

Hi TY forum members happy new year from Colombia, long story below:

I have a 2007 Tahoe, stock 5.3 engine (I've only added an oil catch can and transmission radiator), 180,000 miles with all the maintenance routines.

Four days ago I did a little 300 mile round trip (mixed road between flat and mountains but nothing out of the ordinary). When I was about to return home I stopped for gasoline and out of habit I opened the hood and found drops of oil on the Vortec engine cover (near the clean side of the pcv system there was also a lot of oil and almost the entire air intake tube was covered on the front and bottom side).

The hoses to the right side of the radiator also had oil in it and the lower engine splash shield had some large stains. My first impression was that the transmission radiator installation had failed but upon checking it was engine oil, not transmission oil. With the engine off and then on, I continue checking but I can't see any oil leaking from any hose and it shouldn't because the engine oil doesn't circulate there. The main engine gaskets looks dry (valve covers, heads and oil valley), it is a real mystery for me to know where this oil comes from since the level was only half a quarter below the normal level and I was able to finish the trip without observing new oil stains.

I don't have any lights on on the dash, no check engine, no overheat alerts, the coolant looks normal, and the truck continues running solid. Someone has a clue since obviously it is not something normal to happen. I attach photos so you can observe.

PD: sorry for my bad english and please ignore the temporal heater bypass. The truck does not have an oil cooler installed.

 

[iamdub]

Hi TY forum members happy new year from Colombia, long story below:

I have a 2007 Tahoe, stock 5.3 engine (I've only added an oil catch can and transmission radiator), 180,000 miles with all the maintenance routines.

Four days ago I did a little 300 mile round trip (mixed road between flat and mountains but nothing out of the ordinary). When I was about to return home I stopped for gasoline and out of habit I opened the hood and found drops of oil on the Vortec engine cover (near the clean side of the pcv system there was also a lot of oil and almost the entire air intake tube was covered on the front and bottom side). The hoses to the right side of the radiator also had oil in it and the lower engine splash shield had some large stains. My first impression was that the transmission radiator installation had failed but upon checking it was engine oil, not transmission oil. With the engine off and then on, I continue checking but I can't see any oil leaking from any hose and it shouldn't because the engine oil doesn't circulate there. The main engine gaskets looks dry (valve covers, heads and oil valley), it is a real mystery for me to know where this oil comes from since the level was only half a quarter below the normal level and I was able to finish the trip without observing new oil stains. I don't have any lights on on the dash, no check engine, no overheat alerts, the coolant looks normal, and the truck continues running solid. Someone has a clue since obviously it is not something normal to happen. I attach photos so you can observe.

PD: sorry for my bad english and please ignore the temporal heater bypass.

Do you have an engine oil cooler? I'm wondering if it's leaking and being thrown up by the radiator fans.

Also, you really should connect that pipe that's just behind the air intake tube in the second pic. That's an air inlet for the engine's crankcase.

 

[davidavidd]

Do you have an engine oil cooler? I'm wondering if it's leaking and being thrown up by the radiator fans.

Also, you really should connect that pipe that's just behind the air intake tube in the second pic. That's an air inlet for the engine's crankcase.

Hi @iamdub, no I don't have an oil cooler installed (that is why my post mentions that there is no engine oil circulating in the radiator area), the pipe you mention I have never been able to find where it should go connected.

 

[iamdub]

Hi @iamdub, no I don't have an oil cooler installed (that is why my post mentions that there is no engine oil circulating in the radiator area), the pipe you mention I have never been able to find where it should go connected.

Ah. I'm tracking now. I read that as you saying the engine oil doesn't circulate on that side of the rad (the left side).

That pipe should connect into the air intake tube. It's to get filtered air into the crankcase. Is there not a hole in the back of that intake tube? Usually there's a hole with a rubber grommet for that pipe to plug in to as a friction fit.

 

[davidavidd]

Ah. I'm tracking now. I read that as you saying the engine oil doesn't circulate on that side of the rad (the left side).

That pipe should connect into the air intake tube. It's to get filtered air into the crankcase. Is there not a hole in the back of that intake tube? Usually there's a hole with a rubber grommet for that pipe to plug in to as a friction fit.

Nope, my truck's air intake tube is a straight tube with a high flow filter at the end, it just has the MAF sensor and nothing else. That's why I don't understand where that oil came from, is it possible that it was returned by that crankshaft air inlet?

It was not because of the oil cap because when I removed it to check it was dry, the tube where the oil dipstick enters was also dry (I have heard of engines spitting out the dipstick and then oil from that part).

Today I drove about 40 miles with no new oil "marks". Tomorrow I will look under the truck, however on the floor of my garage there is not a drop of oil.

 

[iamdub]

Nope, my truck's air intake tube is a straight tube with a high flow filter at the end, it just has the MAF sensor and nothing else. That's why I don't understand where that oil came from, is it possible that it was returned by that crankshaft air inlet?

It was not because of the oil cap because when I removed it to check it was dry, the tube where the oil dipstick enters was also dry (I have heard of engines spitting out the dipstick and then oil from that part).

Today I drove about 40 miles with no new oil "marks". Tomorrow I will look under the truck, however on the floor of my garage there is not a drop of oil.

That's really odd that they didn't make any provisions for that air pipe. It's bad enough that it's sucking unfiltered air into the crankcase, but at least there's not a ~1/2" hole in your intake tube allowing unfiltered (and unmetered) air into the engine.

You could get a grommet like this:

, drill a hole and push that pipe into place. You might find a factory grommet on a truck at the salvage yard.


Or, you could slip a breather filter like this:

on that pipe.

I've heard of engines that were boosted or with plugged PCV systems pushing oil out of that pipe. But, I don't see how it'd be enough to spray all over like what yours looks like. If you used a breather filter, you could get one any color other than black and see if it turns black and wet with oil. But your oil is mostly on the front and bottom of the intake tube, indicating the oil came from in front somewhere.

 

[Joseph Garcia]

Do you perform all of your own oil changes? I'm just throwing out there that it could have been a sloppy oil fill, if you don't do your own oil changes.

 

[davidavidd]

Do you perform all of your own oil changes? I'm just throwing out there that it could have been a sloppy oil fill, if you don't do your own oil changes.

@iamdub I am going to install a filter as you suggested, I have several floating around without use.

@Joseph Garcia I do my own oil changes (mobil 1 full synthetic), the engine may have overfilled by about 1/4 of a oil quarter, that's roughly the amount expelled and what was missing when measuring the oil again.

For the moment I am going to rule out a major leak, I am going to concentrate on checking that the entire PCV system is working because everything seems to indicate an excess of pressure in the engine that escaped somewhere.

 

[Ilikemtb999]

Dipstick? I’m guessing crank case pressure issue, just need to find the source. Going thru the system is a good idea

 

[roc1967]

That's really odd that they didn't make any provisions for that air pipe. It's bad enough that it's sucking unfiltered air into the crankcase, but at least there's not a ~1/2" hole in your intake tube allowing unfiltered (and unmetered) air into the engine.

You could get a grommet like this: View attachment 359488, drill a hole and push that pipe into place. You might find a factory grommet on a truck at the salvage yard.


Or, you could slip a breather filter like this: View attachment 359489 on that pipe.

I've heard of engines that were boosted or with plugged PCV systems pushing oil out of that pipe. But, I don't see how it'd be enough to spray all over like what yours looks like. If you used a breather filter, you could get one any color other than black and see if it turns black and wet with oil. But your oil is mostly on the front and bottom of the intake tube, indicating the oil came from in front somewhere.

"It's bad enough that it's sucking unfiltered air into the crankcase"

Wut??

That's not why the crankcase breather house is connected to the air intake tract. Most engines have the crankcase breather hose just open to the air.

 

[hagar]

Check for a crack in the weld area where your dipstick tube is welded to the mounting bracket that goes down to the head. I have seen them crack there, or the spot welds pull apart, and when hot, will shoot oil all over that area of the engine.

 

[ivin74]

your oil is mostly on the front and bottom of the intake tube, indicating the oil came from in front somewhere

I agree, isn't that the side where the transmission oil cooler lines are located? It looks like the transmission may have gotten hot and leaked thu the top fitting connector.

 

[gooffeyguy]

"It's bad enough that it's sucking unfiltered air into the crankcase"

Wut??

That's not why the crankcase breather house is connected to the air intake tract. Most engines have the crankcase breather hose just open to the air.

The PCV system is usually an open system or closed system, only main difference is that the intake air is filtered rather than unfiltered

 

[davidavidd]

Check for a crack in the weld area where your dipstick tube is welded to the mounting bracket that goes down to the head. I have seen them crack there, or the spot welds pull apart, and when hot, will shoot oil all over that area of the engine.

Hi @hagar but if that were the case, the leak would be constant, however it has not happened again. I cleaned all that area and I have not seen any new oil leaks (and I use the truck every day). As others indicate, it was all about a pressure increase in the crankshaft and the oil came out of the PCV system breather.

@ivin74 The transmission oil I use has a very particular smell and color, so I am sure it is engine oil and not transmission oil also the level is OK, it has not dropped a bit.
I'm a little sick right now and I can't bend over but when I can, I'm going to remove the spark plugs, throttle body, and valve covers to check everything.

Thanks everyone for your help

 

[hagar]

Hi @hagar but if that were the case, the leak would be constant, however it has not happened again. I cleaned all that area and I have not seen any new oil leaks (and I use the truck every day). As others indicate, it was all about a pressure increase in the crankshaft and the oil came out of the PCV system breather.

@ivin74 The transmission oil I use has a very particular smell and color, so I am sure it is engine oil and not transmission oil also the level is OK, it has not dropped a bit.
I'm a little sick right now and I can't bend over but when I can, I'm going to remove the spark plugs, throttle body, and valve covers to check everything.

Thanks everyone for your help

Sorry, I didn't notice you figured it out already, just kinda breezed through the discussion.

 

[davidavidd]

Sorry, I didn't notice you figured it out already, just kinda breezed through the discussion.

Oh no, I haven't figured it out lol, but it's the theory that most of us agree on, so far no confirmed source. The oil came from somewhere in the upper right area of the engine.

 

[iamdub]

"It's bad enough that it's sucking unfiltered air into the crankcase"

Wut??

That's not why the crankcase breather house is connected to the air intake tract. Most engines have the crankcase breather hose just open to the air.

What are you referring to as "most engines"? Although, it's irrelevant since the models built over the past 34 years that this forum covers all had the crankcase breather not "just open to the air". They pulled their air from after the engine air filter but before the throttle body. Why would you give dirt/dust a straight shot to the crankcase and oil sump via the cylinder head and valvetrain?

If that's not why that hose is connected to the intake tract, then why else would it be? AFAIK, even lawn equipment engines have the same layout.

 

[steve45]

Welcome aboard, David!

On a different subject, you said you had 180,000 miles on this vehicle. Have you replaced the heater hoses? There is a plastic fitting in them that will fail very soon! Ask me how know!

 

[Dustin Jackson]

Hi TY forum members happy new year from Colombia, long story below:

I have a 2007 Tahoe, stock 5.3 engine (I've only added an oil catch can and transmission radiator), 180,000 miles with all the maintenance routines.

Four days ago I did a little 300 mile round trip (mixed road between flat and mountains but nothing out of the ordinary). When I was about to return home I stopped for gasoline and out of habit I opened the hood and found drops of oil on the Vortec engine cover (near the clean side of the pcv system there was also a lot of oil and almost the entire air intake tube was covered on the front and bottom side).

The hoses to the right side of the radiator also had oil in it and the lower engine splash shield had some large stains. My first impression was that the transmission radiator installation had failed but upon checking it was engine oil, not transmission oil. With the engine off and then on, I continue checking but I can't see any oil leaking from any hose and it shouldn't because the engine oil doesn't circulate there. The main engine gaskets looks dry (valve covers, heads and oil valley), it is a real mystery for me to know where this oil comes from since the level was only half a quarter below the normal level and I was able to finish the trip without observing new oil stains.

I don't have any lights on on the dash, no check engine, no overheat alerts, the coolant looks normal, and the truck continues running solid. Someone has a clue since obviously it is not something normal to happen. I attach photos so you can observe.

PD: sorry for my bad english and please ignore the temporal heater bypass. The truck does not have an oil cooler installed.

@davidavidd Your coolant reservoir looks very red, do you have transmission fluid in there?

 

[Ciro]

The problem is probably the disconnected little hose, that's a PCV hose (Fresh Air) that is connected to the intake manifold, you need to remove the engine cover for access, There should be a port there. Oil is probably coming from the intake manifold PCV port, if the catch can is full or almost full it can suck oil into the manifold, you can install a check valve in the catch can output to avoid that situation, Also check the catch can connections at the PCV dirty side.