97 Deville, coolant inside intake manifold...

[Lake Effect]

First post here, but not a total newb to wrenching on cars.

Son-in-law brought me his new to him 97 Deville, that his mechanic couldn't repair a P300 (random misfire) and P307 (confirmed cylinder 7 misfire) issue that is keeping him from getting the car tagged.

I repeated the original work, and did some more.  Fresh plugs and wires, replace the coil associated with cylinder 7 because of a corroded terminal, and repaired several vacuum leaks.  When I had the throttlebody and the spacer block (EGR port) out to clean them I noticed liquid inside the intake manifold, in the valleys.  I'm assuming it is coolant, it's the right shade of green, and I learned the car does "lose" coolant when it's hot out.

I know that the intake manifold doesn't have any coolant running through it (nylon 66), and there shouldn't be any coolant on the other side of the intake manifold gasket, so how is it getting into the manifold?

Looking at the plugs, #7 looks unhealthy, maybe a bit oily, but definitely darker than it's supposed to be.  Cylinder 2 (opposite corner) looks correct with the insulator a nice light brown.  All the others have very clean, very bright white insulators.  I'm suspecting coolant is getting into the manifold, occasionally fouling the cylinder 7 plug at idle, and the other cylinders are receiving a regular steam cleaning, except for Cylinder 2, which is getting no coolant.

The northstar engine runs great, the miss appears to be at idle.  The mechanic indicated that he had the injectors out and cleaned.

The EGR tube is clear, the port at the TB spacer had a bit of buildup, but it wasn't blocked.

It appears that the throttle body has coolant running through it, what are the chances of the coolant in the manifold coming from there?

[rockfangd]

Hmm interesting. 

The Throttle body has a coolant warming setup. It is a dry intake.

Can you confirm it is coolant or are you sure it is?

You could bypass the Throttle body and see if it helps.

 

[BodybyFisher]

Given the info you have provided, the misfire in #7, discolored plug and the appearance of coolant, and given that you have taken steps to find the misfire ie plugs and coil (I trust you checked the ignition wires), I would test for a blown head gasket.  Go to NAPA and order the Balkamp Block Tester and do the test.  If the head gasket is breeched combustion by products will be in the cooling system and the test will confirm that instantly.  

Let us know what you find, good luck

[Lake Effect]

Thanks for the help!  The plug wires are also new, installed with the new plugs to avoid creating carbon tracking...

I am going to take both bits of advice, bypassing the TB, and doing the coolant test.  I'm really hoping it's not a headgasket, simply because even though I've found I enjoy working on the intake and ignition systems, I don't like to actually crack open a block.

[BodybyFisher]

I hear ya, we can talk about that later.  Do your test and see what you find..  

[Lake Effect]

The good news is that the Block Tester test (from the Department of Redundancy Department) showed no combustion gases in the coolant.  Pretty happy about that.

I have the intake system apart again to dry out the intake manifold and will bypass the TB warming coolant circuit during reassembly.  I'll also drop a clean plug into that #7 slot, clear the codes, and hope for a simple solution...

[BodybyFisher]

I need to look at the throttle body, I am very surprised that coolant can get into the intake AT ALL.

That coolant circuit is used to warm incoming air, or you can get frost and ice in the throttle body.. I don't know if it can freeze up, but, in the past we have had members want to by pass the throttle body thinking that the air charge will be cooler and improve performance and the guru recommending against it, for tha reason of icing.  If you do by pass it, you need to keep that in mind, I would rather find the problem.

I would remove the throttle body and see what is going on.   I will check my service manual to see how it could leak.   Its hard to believe that you could see green or orange coolant at all.   I am surprised because if this is possible, to get coolant in the intake, there is a risk of hydro-locking the engine and blowing a rod out of the side of the block. GM would never risk a potential failure like this, and I have been around this site for 20 years and NEVER heard of anything like this happening.    I do no believe the TB heater circuit can cause this.  Please look closely.   Note, if you remove the throttle body, on the 96, there is an ORING that will not fit after you remove the throttle body, and you need the ORING.   I don't know if this holds true for 97, however, but be aware and ask a caddy parts department what seals are used between the TB and intake.

I would want to say, don't worry about the water in the intake, but I don't know how much could be in there and you might open the accelerator and the engine and suck water in and lock up.  This is a first, never heard this before happening, its does not make sense.

Could water gotten into the filter intake in deep water or heavy rain or puddles?  How sure are you its coolant?

[KHE]

The only way coolant would get into valley of the engine is if the water jacket was cracked or there was a crack in the throttle body heater circuit.  There isn't any other direct path for the coolant to get into the valley.

If it was a small amount of coolant, it might be able to be sealed with a dose of bar's leaks golden seal to the lower radiator hose.  That used to be installed at the factory until about 2001 or so.

[Lake Effect]

If it's coming from the throttle body, it's not actually difficult.  There is a flat gasket between the TB and the spacer, the gasket forms a wall of the coolant passage below the throat.  I didn't see any evidence of a leak at the gasket, but bypassed the TB anyway.  Again, I'm still in troubleshooting mode.

I have images of the coolant in the intake, if I can figure out how to get them from the new phone to the chromebook....  I'm going to try something here....

link to shared images of coolant hell

No idea if that will work...

Anyway, cleaned out the intake again, bypassed the TB warming lines, argued with that Oring until it fit again, cleared the memories by disconnecting the battery for about and hour with the headlight switch on, then started it back up.  On the second start of the vehicle, after driving about one minute, the check engine light is back on, didn't pull the codes yet.  I'll pull the intake stuff again tomorrow and look for a new puddle....

[Lake Effect]

Kevin, you posted while I was replying...

When I said it was in the valley, I meant inside the intake manifold, in the depressions, not in the valley between the heads under the intake manifold.  I apologize if I wasn't clear.  But, to your point, assuming it's not the TB heater circuit, is there a water jacket that could crack allowing coolant to get into the intake at the driver side end of the manifold?

I'm hoping the picture I included (link actually) works in the previous post, it shows the deep green coolant in the first two depressions (valleys), with the closest one having more than the next.  I'm going to include another link here, the image was taken before I removed the spacer/EGR block.  Looking at it, I can see evidence of coolant at the lower edge, perhaps the coolant was coming from the TB circuit and the codes I'm getting now are just the next step.  It does sound/feel like a misfire is still occurring at idle though.  I did replace the #7 plug again when I wiped out the manifold earlier.

BodyByFisher, I did make sure the air filter was dry, and the liquid is definitely green coolant.  It feels and smells like coolant.  You are certainly correct about the risk of hydrolock, if the pictures are visible, you'll see that it's quite a bit of liquid sitting there waiting to make it's way into a cylinder.  I'm wondering if GM placed the intake runners from the top of the manifold, or if the draw from the bottom...

Third and fourth images have the EGR spacer installed

[BodybyFisher]

I had to look back to see if I did a poor job of reading your post and misunderstood you but you said this:

"I know that the intake manifold doesn't have any coolant running through it (nylon 66), and there shouldn't be any coolant on the other side of the intake manifold gasket, so how is it getting into the manifold?"

That is where I ran with this, water IN the manifold.  

That is a HUGE difference compared to coolant under the manifold.

So you seem sure that its coming from the TB heat circuit?

[KHE]

Are you sure the liquid inside the intake is coolant?

[BodybyFisher]

Ok Im confused now Im sorry, it is INSIDE the intake?  

[Lake Effect]

Smells and feels like coolant, also green.  If it's there again tomorrow I'll taste it... 

Are you able to see the images?  Some are better than others, the first ones that show still have the EGR block installed, the last two are just the manifold.  The last two make it easier to see the puddle in the first valley.

[Lake Effect]

5 minutes ago, BodybyFisher said:

 

That is where I ran with this, water IN the manifold.  

That is a HUGE difference compared to coolant under the manifold.

So you seem sure that its coming from the TB heat circuit?

The liquid is in the intake manifold, not under it.  I bypassed the TB circuit today and cleaned out the manifold, then ran the car.  I'll check again for liquid in the intake manifold again tomorrow, if it has returned, then I know it's not coming from the TB heater circuit. 

 

 

[BodybyFisher]

Not good if its inside.  I still don't know how it gets from the TB heater circuit into the intake.  I am happy to hear that you did a block test and it was negative.  I am stumped on this one

[rockfangd]

I am also. 

Have not run into one with coolant in the intake yet.

Have seen oily in the bottom of about every one that had not been apart in a long time (or ever)

[Cadillac Jim]

I'm not convinced it's coolant.  If it has a sweet taste, it's probably coolant; spit it out and be kind to your liver & kidneys.

If you use the OEM AC/Delco air cleaner and your intake system is all in good condition (no cracks, clamps tight), you won't get water through the intake.  The element is reinforced with a steel mesh and water will clog the air cleaner and kill the engine with vacuum.  If you run an aftermarket air cleaner element that isn't designed to hold up to massive amounts of water, then if you get into deep water and water comes in the intake, you risk hydrolock.

[KHE]

What is green coolant doing in a '97 car?

[Lake Effect]

Like I said....  new to the son-in-law car....  previous owner problem.

[Lake Effect]

Resolved.  

The 'paper' gasket between the throttle body and the EGR spacer/block was allowing coolant to weep up into the throttlebody bore.  It was probably drawn up into the bore by the venturi effect of the intake air rushing past the imperfection.   The throttlebody itself is cracked at the water jacket.  Once in the bore, it went into the EGR spacer/block and pooled against the intake manifold lip before being carried over the lip into the intake manifold.  Because the manifold is molded with valleys and ribs for structural strength, it also has traps for the unexpected coolant to pool in.  It tends to pool closer to the TB, since that is the source, and is pulled into the #7 cylinder upon acceleration, causing a misfire.  It also is drawn in smaller quantities into the 6 of the other cylinders, in lower quantities, where it acts like a very primitive water injection system.  The coolant affects the combustion process, creating a small amount of white smoke out the exhaust pipe, unlike plain water which would not affect the color of the exhaust.  Another hint in the diagnosis is the slow loss of coolant, not found outside the engine or cooling system.

Bypassing water jacket in the Throttlebody (thanks rockfanged) confirms the issue, but you need to be sure to remove the TB and EGR spacer/block to manually clean/dry the inside of the intake manifold, and then replace the slightly fouled sparkplugs.

Bypassing the water jacket is a temporary fix, as throttlebody icing can occur, even in a warm climate, although the circumstances required to ice the TB are pretty specific.  Bypassing is the semi-permanent fix until the throttlebody can be replaced.

Inspection of the metal parts for cracks is difficult without magnaflux technology, but it is pretty safe to say that the fiber gasket is going to be the weak link in a pretty robust system.

Images of the coolant in the intake manifold are included in this thread, and since it is the first ever occurrence of the problem that will occur as gaskets fail over time, I am exercising the right of naming of the problem.  It is the "Kobayashi Maru leak", deemed impossible for decades, yet Murphy always sides with the hidden flaw.

Thank you CaddyInfo forum for your patience and wisdom.  Working with an engine one is not familiar with can be a bit scary at first, but you got me through it.  I'm going to be a little sad to see the land yacht go, it was a very comfortable diversion from the race cars and motorcycles.

If you are in the Atlanta, Ga area and need help turning some wrenches, I may be able to help.  I'll remain subscribed to this thread, so if you reply to it, it will let me know by email notification and I'll get back to you.

Best of luck and have fun,

Dale Seeley

[Cadillac Jim]

Kobayashi Maru leak, it is.  But, you reprogrammed the simulation by disabling the throttle body cooling (the DFI equivalent of a heat riser or temperature-controlled intake) and by fully disassembling the throttle body and examining it minutely.

Browse the other topics occasionally.

[Lake Effect]

slight update/retraction....  

Not the gasket, as I was mistaken when I thought the water jacket in the TB  was exposed to the gasket.  It's not.  There is a crack in the throttlebody.  That's something I would not have expected, but this car has led a hard life with the previous owner... For example, even though the body shows no damage, the frame is bent enough to make alignment impossible, even with all new front suspension and control arms...

Again, I would like to express true gratitude to the forum for your efforts.  

[BodybyFisher]

Ahh, a fellow Star Trek lover.  My former name here was Scotty, and posts still exist!  Going to a Star Trek event with my daughter in NYC this weekend.

Would love to see photos.  Any ideas how the TB cracked?  I doubt Hotlanta gets cold enough.

This is a first!  Good work, thanks for sharing.  

And you are correct, it doesnt need to be cold outside to cause icing, the guru noted that.  

[Cadillac Jim]

An in-depth body shop can straighten your unibody so that you can properly align the wheels.

A cracked throttle body certainly punctures the mystique of coolant leakage (no pun intended!).  Two possible causes are bolt over-tightening anywhere on the throttle body, and over-stressing, as in dropping a heavy body on the intake.