About a month ago, my '96 GT developed a really bad misfire on the way to work. A quick, lunch time inspection didn't reveal anything and that night I checked all the plugs, wires and tested the coil packs and didn't find anything but the misfire was gone when I put it all back together. CEL never flashed and no codes were set. My initial suspicion was I must not have seated one of the plug wires really good a few weeks before when I was doing some work and it had worked its way loose. I ordered some plug wires though in case one of them was going bad - they appear to be original with 125K miles. About two weeks later, the misfire returned. I decided to replace the wires but this time I noticed water on the #1 plug boot and found some sitting on the spark plug in the hole. It was probably there the first time but I didn't notice it because I didn't look down the hole with a flashlight - I just pulled the plugs and any water would've just run down into the cylinder. I found water in lessening amounts in the #2, #3 & #4 holes too. There was no evidence of water in the block valley though and no signs of cracking on the intake, as best as I could see with a flashlight and dental mirror. I cleaned dried everything out and put it all back together and have been checking daily for water in and around the #1 plug hole, spark plug hole galley (is that what that's called?) the coolant crossover and in the valley and spot checking in different states - cold in the morning, hot after I get to work, idling, running at 2000 RPMs, after it's been sitting for a couple of hours, right after a hard run. I didn't find anything, not a drop for several days and then finally, after 3 or 4 days I found about 3 drops of coolant on the #1 spark plug wire boot (not enough to cause a misfire yet though). To me, that sounds more like an intake gasket leak as I don't think a cracked intake would trickle so slowly like this for a prolonged period of time once it got started - it should go pretty fast once that first crack develops, right? Does any one think that this is the first ominous signs of a intake that's about to give way? I actually have a PI intake in the garage I could use in an emergency but it's an all plastic design and so this episode prompted me to go ahead and pick up a newer aluminum crossover PI intake, which should be here in a few days. It sort of seems like a moot point since I'll soon have most of the parts I need and can just go ahead and replace it but the reason I ask is that if it's just a leaking gasket, I can manage that until the weather and my schedule align and I can do the PI upgrade at my convenience. If it's a intake that's on the verge of exploding and leaving me stranded, then I've got to jump on it immediately and can't take the car out of town until it's fixed. Thanks!
When I was buying my 99 GT I was inspecting the engine while running in the dealer parking lot (car had 48k on it) I was about to sign the deal when I noticed a bit of pooled up coolant near the t stat. As I stared at it I saw a tiny bead of coolant seaping out of the plastic intake. It took about 1 minute to leak about the size of a BB, so yeah it can leak very slow, I couldnt even see a crack. They ended up replacing the intake before I bought it. At the time I knew nothing about Mustangs.
I am assuming that it is coolant in the spark plug holes and not pure water. A coolant pressure test may be a good idea. It will give you an idea how bad it really is. Also, it may pressurize the system enough to allow you to better pin point the leak location in your driveway. Could try a re-torque of the intake manifold bolts. This will rule out a loose bolt. And Yes I think it could just be an intake gasket. However, IMO it would be hard to justify the work to replace just the gasket if you are planning a PI swap. Besides, what would you do if after tear down you found the intake was indeed cracked?
Yeah, either way, i'm doing the PI swap, it's just a matter of am I taking off work tomorrow and changing it in the freezing rain or am I waiting until a nice mild weekend to do it. Yep, it was coolant - I was hoping it was just some stray water but there was no mistaking the smell or taste when it flew up in my face when I hit the compressed air
Bumping this thread with updates... finally started seeing moisture in the valley and finding small puddles under the car over the last couple of weeks so I took advantage of Christmas break and pulled the intake this week and put a PI intake on. Turned out to be a intake gasket failure at the coolant port on the front of the passenger side head and not a cracked intake - you could see the orange-brown stains on the gasket where coolant was escaping past the seal. There was a small pitted area on the mating surface of the head at that spot which may have contributed to the failure. I may post a thread about the swap in Talk later if anyone is interested in the gory details. Car runs great and pulls strong all the way to 6K now... and, no leaks.
I didnt think the PI intake would fit on the 96 non-PI heads... you mention the PI cams & intake, but not the heads. If it does fit, what mods did you have to do? I had the older, non alum crossover intake split on me right by the T-Stat, but I was lucky enough that it was a big crack and water shot out of it like a small geyser, so it was easy to find.
Yep, I've got the PI cams and now the PI intake but the heads are still the original NPI heads. A PI intake will fit and works great but there are a few issues that have to be dealt with in swapping it over to NPI heads. The intake port mismatch is really not the problem you might imagine it to be, but the mismatch between the coolant ports is thornier but pretty easily managed. Here's an old, but helpful thread about it http://www.stangnet.com/mustang-forums/430490-parts-needed-pi-intake-swap-pics-inside.html and a search will turn up a bunch more threads.
