Page updated on 05-20-2018

3800 series 2 won't start after lower intake manifold gasket repair.

10-23-2011, 06:40 PM
Hey guys I'm hoping you might be able to help me out, I'm working on my car and the current status is that I can't start it after changing out the lower intake manifold gasket.

It's a 97 park avenue, basic, with a 3800 series 2 engine. I believe around the 75,000 mile mark (I'll have to double check to be sure, but it's something close to that.)

I'll fill you in with a little back story. About a month ago there was some coolant slowly leaking. I couldn't figure out where since there were no puddles underneath the car. I looked around and saw that the previously replaced water pump had just a little bit of what looked like dried and burnt coolant around it. After taking it off it still seemed to work just fine and I resealed it with a new gasket. I flushed it with the hose, ran it, and drained it. I put in about a gallon of premixed coolant into the radiator and about another half in the reservoir. I ran it and had to get going to work, drove it and about 3 miles in the temp gauge kept climbing. I pulled over let it cool off, topped of the radiator which was not very warm and kept going. About a mile later the gauge kept climbing and I stopped and did it again, but this time after restarting it droved very rough and felt like I lost a cylinder. another mile later, it I stopped and once more I topped it off, but this time I couldn't restart it. I noticed that the inside of the radiator was very warm as I saw a little steam come out as I refilled it, but the cap was cool, and it didn't draw from the reservoir even though I made sure it was very patent when I flush and cleaned it out. ( maybe a loss of vaccum to draw it in?)

I had it towed back to my house and pulled the spark plugs. Fresh coolant shot out of cylinders 3 and 5 (closer to the front and throttle.)
I let them dry, put them back in there and tried again. with about 2-3 seconds it tried for a second and then sounded like it ceased. I pulled them again and this time cylinders 1 and 3 were flooded with coolant, this after only about 3 seconds of the starter trying.

I did a little research and found a few different possibilities for that to happen. Of which including heads/ gasket failure, intake and manifold/ gasket failure of upper and/or lower. I looked more and it sounded more and more like the intake was what was causing the trouble.

I get an estimate for the job and it's easily over 2 grand, so I decide to do it myself. I start by taking it apart. First the plugs, and the wires and etc.I take off the intake manifold and there's a nice puddle of coolant just sitting there. I clean that out, inspect the plastic manifold, nothing really stands out... so I go deeper. I pull off the intake. low and behold the two lower intake manifold gaskets are in pretty bad shape, with seals bowed in, a little bit of cracking and coolant sitting in cylinders 3 and 5 with the rest pretty clean and dry. I get a new set of LIM gaskets and put them in, with a little dab of RTV sealant at the joints and carefully put the aluminum intake back on with a new coolant temp sensor on it. With the plugs still out and the wires disconnected from the plugs I cranked it for about 10 seconds to remove the coolant I couldn't reach that was siting in the cylinders. I torqued the intake bolts in sequence, and the same thing with the plastic upper intake manifold( with new main seal on the upper as well to be sure). I put everything back the way it went, with new plugs, wires and air filter, cleaned the throttle body out with some break cleaner, cleaned up the pcv valve and hooked up all the wires, vacuum hoses, fuel lines... everything. I go to start it and it doesn't want to start. It does cycle but there's no real firing going on. I look the thing over and it turns out I think I swapped the cylinder 2 and 6 spark plug wires. I try again, still no luck. a little frustracted I pull the plugs, look them over and they are a little wet with gasoline. Each one looks like it was flooded a little bit, to the point I could whip the spark plug with my hand and a few drops of gas would fly out and hit the floor.

with them out I figure maybe the fuel rail needs to be primed so it's shooting evenly into the cylinders. I cycle it for about 10 seconds.
I let them dry, put them back in and plug everything in... still no luck. I think to myself," okay there's fuel, air...maybe there's no spark...". so I pull them one more time, line them up, have my brother crank it for about 2 seconds and I see sparks from each one.

So I have fuel, spark and air, but it still won't start. It's not ceased otherwise I wouldn't have been able to cycle out the coolant and well, it wouldn't cycle in trying to start.

when I try starting it I have noticed that there is some firing going on, but it didn't seem very continuous or in sequence. I looked the plugs over and still everything is as it should be, so I'm really lost at this point of what it could be.

Is there something else timing related that would have been thrown out of tune with these part being moved around or coolant having been in the system...?

Any and all advice at this point would be greatly appreciated. this is the first time I've done an engine repair of this magnitude and I want to figure out what I missed so I can get this thing running great again.

thanks guys!


10-23-2011, 07:20 PM
With strong spark and fuel it should start, are all the harnesses and sensors reconnected, recheck all that, try spraying starting fluid into the throttle body, make sure all the large vacuum hoses are connected, you missed or did something if it ran before, try disconnecting the maf if all else fails, .also as a side note change the oil and filter, if not done do it now.

10-23-2011, 09:14 PM
When you removed the UIM, did you remove the throttle body to inspect the area behind it? I do not see where you replaced the UIM, which is a very common failure behind the T/B. In addition, the plugs will not fire hot enough to start the engine, once soaked with coolant. If not done yet, change the UIM and then the plugs.

Did you see something similar to this pic, once you removed the UIM? If so, you need to replace the UIM!

10-24-2011, 09:22 AM
With strong spark and fuel it should start, are all the harnesses and sensors reconnected, recheck all that, try spraying starting fluid into the throttle body, make sure all the large vacuum hoses are connected, you missed or did something if it ran before, try disconnecting the maf if all else fails, .also as a side note change the oil and filter, if not done do it now.

I looked them over again and they all are connected, starting fluid put in and vacuum hoses connected. It did run prior, and the thing is it does try to start, but something in the back of my head makes me lean towards some sort of miss fire or something out of sync.

I regards to hotz28's comment, yes it did look just like that. I did put the old one back on after cleaning it out, with a new upper intake manifold seal and seal at the throttle body, and cleaned out the pcv valve.

now that you mention it you may be onto something. I only put in water so far for the coolant, so what i'm thinking it that if that old upper intake is warped or out of shape then as good as the new seal is it may not be able to do it's job if the upper is not formed well around it. If it's not sealed the way it's supposed some of that water could be getting into the cylinder, and though it may not be filling up, it may be preventing it from firing and the gas/water mixture may be what I found in those spark plugs when I pulled them and since there was no color to it yet nothing stood out, it did smell like gas but in hindsight perhaps not as strong as straight gas.

does this sound plausible? I hate to tear it apart again without having good reason. Should I try starting it again, collect some of that fluid that I found in the spark plugs and try to ignite that to see if what's going in is combustible?

thanks for the input so far guys.

10-24-2011, 11:14 AM
The upper intakes cracked where the egr passage runs next to the coolant passage behind the throttle body, if this prevented the car from starting you would have water on the plugs, do they smell like gas when you inspected them?

10-24-2011, 11:24 AM
The upper intakes cracked where the egr passage runs next to the coolant passage behind the throttle body, if this prevented the car from starting you would have water on the plugs, do they smell like gas when you inspected them?

They do, but being I only have water in there for coolant right now I'm wondering if maybe the two mixed so there's still the smell but it's not combusting because of the water.

Tech II
10-24-2011, 01:16 PM
$2000 for a lower intake gasket and upper plenum?

In that picture, there is only one way that coolant can fill the lower intake like that.....As Maxwedge has said, where the EGR tube goes up through the upper plenum, the plastic that surrounds the tube, degrades and leaks coolant....need to replace the upper plenum....and suck the coolant out again.....makes sure oil and filter have been replaced....

when you have it all together again, do this......leave plugs out and disable fuel and spark......crank this over several times(helps remove residual fuel/coolant)....makes sure new plugs are clean and dry.....install them and wires......remove the O2 sensor in the the exhaust manifold(one before the cat)....enable spark only......crank the vehicle several times(this helps to burn residual fuel) enable hold accel pedal to floor and crank vehicle, as it starts release the pedal......

If car starts and runs, shut down and install O2 sensor....start vehicle.....if it doesn't start or starts, but then runs poorly, you may have coolant in the exhaust......have had to jack up the front end, to allow coolant to drip out of the muffler, so it would start....

10-24-2011, 02:14 PM
[quote=Tech II;6935482]$2000 for a lower intake gasket and upper plenum?

yeah mostly the cost of the time, my dad went around to get estimates from local places (dealerships mainly). This is actually his car and I'm the more mechanically inclined family member so I figured I'd try and save him a couple bucks.

question though, how would I go about disabling the fuel temporarily and safely? is there a valve somewhere I can shut off?

and as for the O2 sensor, is it necessary to use a special tool or is there any other means of removing it safely without damaging anything?

10-24-2011, 06:39 PM
A dedicated 02 socket can be bought for about 12.00, to cut the fuel just hold the pedal to the floor cranking, that is the clear flood mode. Or pull the appropriate fuses for the pcm and fuel pump.

10-24-2011, 07:56 PM
I would probably get on the 'net and order one of these right away. They have a heat shield on the plastic UIM which protects it from damage, in addition to a reduced stovepipe if it hasn't been replaced yet. I see you're in Canada. The guy at ineedparts is very reasonable about shipping to Canada, kind of a rarity in this world.
At least you have the LIM gasket done, so the UIM shouldn't take too long. Cleaning all those LIM gasket surfaces was sure a pain!

If you can, get a thread chaser to clean the UIM bolt threads. That way you will know the torque will be accurate.

Good luck!

10-25-2011, 04:58 PM
you guys called it. this is what I saw when I pulled the thing off.

I put the new intake and cycled the coolant out and it started right up.

two things now are still on my mind; one, how do I know it's not still leaking a little bit in there without taking it off again, and two, there was a LOT of smoke coming out of the tail pipe for about 5 minutes or so until I warmed it up and floored it. That seemed to clear it up. It was a thick grey, which I guess was probably the coolant that was in the exhaust.

Tech II
10-25-2011, 07:34 PM
Yeah, that was probably coolant in the exhaust.....

Did you look at the upper plenum where the EGR tube passes through it? Did you see the hole where the coolant went through? As long as you put that gasket on right and torqued it evenly, it shouldn't leak.....

Just for ha-ha's, I would change that oil again...

Add your comment to this topic!