Mysteriously wet intake tube. (?) And vacuum leak?

[Traz]

So my 2004 Buick Lesabre (3800 S2) was running rough when it got warm. I found the cap was missing from the little vertical tube that comes up from the brake vacuum hose. On mine it just has a cap. Well, the cap was laying off to the side. I've put it back on a couple of times. I think it was fitting loosely. So today I replaced it with a vinyl cap that fits tightly. Hopefully it doesn't come off anymore. Then I thought, why is it coming off at all? Shouldn't there be a vacuum? So I replaced the PCV valve. Even though it seemed to be in good order, I replaced it anyway because I had a new one sitting around. I took the oil cap off and put my hand over the hole. I couldn't feel any pressure. I put a paper towel in front of the oil fill hole, no movement there.

Now the mysterious part.

The car has been parked for a couple of months, and when I opened the hood, I could see the rubber intake hose (the IAT sits in) looked totally wet. I felt it and it was very gummy and greasy. It was difficult to remove (like wrestling a greasy pig) and I could see that it was all wet inside as well. Now the mysterious part of this story is this: The air box was completely clean, except for the outer side of the lip (where the hose attaches to) was greasy wet. The air filter was normal. Then I checked the throttle body. The screen was clean as a whistle. I took the retaining "C" pinch ring out, and took the screen out, and the inside of the throttle body was clean and dry.

Now over the last few months I've noticed the coolant has been going down, about an inch lower in the reservoir. The level goes up to the "cold fill" line now when it is fully warmed up. So I'm losing coolant somewhere.

I don't see any coolant anywhere. Everything is nice and clean. I just changed the oil and it looked perfectly fine. Nothing under the oil cap. No smoke out the tailpipe.. nothing like that.

So I'm wondering if maybe there is a leak between the throttle body and the plenum. Or maybe that pesky EGR tube is acting up. I just replaced the LIM ad UIM gaskets only a year and a half ago and about 20k miles ago. I put the smaller EGR tube in when I did that. Everything around the area looks fine.

Just wondering what Y'all make of this problem.

I just ordered a coolant dye kit so I can figure this out. Also, tomorrow I plan to clean the IAT sensor with some MAF cleaner, and also clean out the intake hose.

I'm wondering if anybody has an insight into this while I'm waiting for the dye to arrive.....

I also have a P0496 code, which I think came on during the vacuum leak

thanks in advance.

TRAZ

 

[BuickGirlFromMars]

To me, you r theory of the intake gasket is not a bad one. But the 2004 should have the factory improved gaskets.
The IAT sensor doesnt need cleaning with MAF cleaner, but if you want to clean the oil off it then that is the best spray to use. make sure to clean the MAF sensor with the MAF cleaner. DO you have leaky valve cover gaskets? And did you do the EGR stovepipe repair on your intake?

I would also checkout your purge valve on your intake, does it let you pull air through it when car is off?

 

[Traz]

To me, you r theory of the intake gasket is not a bad one. But the 2004 should have the factory improved gaskets.
The IAT sensor doesnt need cleaning with MAF cleaner, but if you want to clean the oil off it then that is the best spray to use. make sure to clean the MAF sensor with the MAF cleaner. DO you have leaky valve cover gaskets? And did you do the EGR stovepipe repair on your intake?

I would also checkout your purge valve on your intake, does it let you pull air through it when car is off?

Yep, I put in the aluminum lower gaskets, the redesigned ones, and I also put in the smaller EGR tube that came with the plenum kit. No leaky Valve cover gaskets, I replaced those about 70k miles ago

 

[Traz]

I'm not sure if the wetness of the intake tube is oil, or if it is antifreeze. I looked all over the place for the source of it, like ripped CV boot. I kind of think it is glycol from the antifreeze. I can't really tell what it is.

 

[Traz]

The purge valve. Is that the one for the evap system? I'll pull if off tomorrow and see If I can blow through it.

 

[BuickGirlFromMars]

I'm not sure if the wetness of the intake tube is oil, or if it is antifreeze. I looked all over the place for the source of it, like ripped CV boot. I kind of think it is glycol from the antifreeze. I can't really tell what it is.

Take a white paper towel, napkin, or toilet paper, and lightly dab it. If it comes dirty , but not oily, try cleaning the area with MAF cleaner or rubbing alcohol, driving more, then trying again. It should be clear if its coolant , but darker if its oil)at least the darkness it is on the dipstick at the same time)

The reason for clear is if you mop up a little dexcool with a paper towel it wont show its orangeness until you get enough on it. Hard to explain but i think you can understand what im saying?

 

[Traz]

It seemed to be dirty, it made the rag I used and my hands dark. But how the intake tube can be covered inside and out and the the air box and throttle body be clean. That is really strange. I'll take another look at the valve covers and another look around tomorrow.

I flushed all the dex-cool out (really well) about 70k ago and put in the prestone universal stuff. It's kind of yellow.

 

[HotZ28]

 

[Homer Jay]

Check the coolant elbows and water pump. They could have a slight leak which may not be apparent while the engine is off.

 

[Traz]

thank you! I'm going to look at it this morning.

 

[Traz]

I have a new theory. I wonder if the rubber itself is breaking down:

Earlier this winter (January I think) we had an extremely wet period of time. It rained for two weeks or more every day. And this is also the time that the engine started running rough. However, the other rubber things seem unaffected. This still leaves more questions.

What Are The Main Causes Of Rubber Degradation?​

Time is probably the biggest factor in rubber degradation, but there are other factors that could accelerate rubber degradation. There are many types of rubber and each one has a slightly different set of factors that causes it to degrade. Here are some of the common reasons why rubber degradation is accelerated.

• Oxidation
• Exposure to UV light
• Heat (keep rubber as cool as possible)
• Humidity (keep it below 65% RH)
• Lack of use
• Exposure to certain chemicals such as certain Oxidizers, Acids, Oils, and Alkalis.
• Transfer of chemicals from hands to rubber, which can degrade it; like DEET and Sunscreen to rubber
• Certain bacteria (See References Below)

 

[BuickGirlFromMars]

It seemed to be dirty, it made the rag I used and my hands dark. But how the intake tube can be covered inside and out and the the air box and throttle body be clean. That is really strange. I'll take another look at the valve covers and another look around tomorrow.

I flushed all the dex-cool out (really well) about 70k ago and put in the prestone universal stuff. It's kind of yellow.

Oh, that shows up even more difficult. is it prestone platinum? That shade of green/yellow is very faint lol. oddly becomes green over time.

 

[HotZ28]

I have no idea how a valve cover leak, water pump leak or coolant elbow leak could contaminant & degrade the rubber in T/B intake hose??

 

[Traz]

Yeah. Me neither.

So, because the car was sitting for a couple of months, whatever caused it must be something in the environment, or a chemical reaction. Not anything mechanical like a CV boot spraying up or something like that.

Sadly, the dye that I put in the coolant didn't show up anything. I put it in yesterday and drove it about 30 miles. After dark I looked all around anywhere there might be coolant, actually everywhere period. I did not see anything.

The cap keeps blowing off and making a vacuum leak. It's the cap that fits over the little vertical tube that comes up from the brake vacuum hose - at the fitting where it fits into the plenum. I've replaced it a few times with new ones, they are vinyl caps. and they fit pretty tight. It must take some force to blow it off.

I'm wondering what's causing that. If I have another smaller vacuum leak that is making the car run rich, and then the next time I start it it coughs and sputters and blows off the cap. The 30 miles it ran really good. I haven't started it again, but if the pattern continues, the next time I start it it will have a rough start and maybe blow off that cap again.

 

[Traz]

When I get a chance I think I'll pull the spark plugs and see what they look like. Maybe it's time to redo the plenum (upper gasket) and see if there's something going on in there.

If I can't figure this out, I'll have to take it somewhere and just pay the man. 🙂

 

[Traz]

And by the way, after driving it around the intake tube completely dried out. Inside and out. The only place that's still wet is the outer lip of the air box, where the intake tube connects. Where the intake tube and air box connect.

I pulled the IAT sensor and the MAF and cleaned them both with some MAF cleaner before I drove the 30 miles.

Still wondering what is going on with this motor.

 

[Traz]

I finally got around to working on the car again today, it's been in the garage this whole time. My 96 year old dad is keeping me very busy....

anywho, BuickGirlFromMars was totally spot on... it was the vapor purge solenoid this whole time. I took it off, and blew through it and it was like blowing through a straw. I've never had one fail so spectacularly. This is the third one I've put on this vehicle. I always buy OEM from RockAuto, so I expect them to last but I'm starting to rethink that.

The engine is running a lot better now. The LTFT went from -14.8% to -6.3%.

So at least the engine is happy again.

The spark advance started out at 18.5 degrees before replacing the purge solenoid. Now it is reading 23.5 degrees. Is that a bad number for this engine?

After heating up the car, the moisture disappeared from the intake tube.

And I looked around tonight for the coolant leak. (I put in the dye a couple weeks ago) still no signs of where it's going.

 

[Traz]

I found the vacuum leak, It was the Evap Purge Solenoid, the one on top of the engine.

But I was still losing coolant. Couldn't see where. So I parked it for a couple months this winter while we ran away to Florida. When I got back the intake tube had a thick coat of coolant covering it. I had put in the dye last year and so it was easily visible. It's like the coolant condensed all over the rubber intake tube. Coolant pooling in the lower intake manifold valleys, by cylinders 5 and 6, under the throttle body. Coolant making its way down the fuel injector port #6.

The lower intake manifold had some pitting at the two coolant ports (that feeds the throttle body) - not perfectly smooth. So I took the LIM out, cleaned it up and put a little JB Weld there. carefully sanded it smooth, then a little steel wool. So hopefully those ports are going to get a good seal. I ran a magnet inside the LIM to get all that steel wool shavings out, then flushed it out with water.

Put it all back together and new spark plugs and wires. Runs very smooth now.

 

[HotZ28]

No mention of the replacement of the UIM?? 🤔

 

[Traz]

No mention of the replacement of the UIM?? 🤔

Yup, sorry! New Plenum (UIM) and gasket (Dorman), new aluminum coolant elbows. New pcv valve and O-rings. New injector O-rings, cleaned the injectors up. I lubed all the O-rings to make sure none of them rolled on me. I used a mirror to inspect the elbows to be sure those seated properly. I used the universal prestone, I think it's yellow to lube the elbows. That seems to work pretty well for me.

I know lots of people recommend the ATP parts, but I am crossing my fingers with the dorman parts. I used AC-Delco OEM (Gold) sparkies and sparky wires.
I already have a big tube of Permatex Dielectric Grease - 22058, so I never need to buy that.