Villiska

Alright, I'm back with some fresh information and a fresh thread. So, I have a 1999 V6 Mustang with 202k miles on it. She's ran great apart from silly issues up until about two months ago. It started with random fluctuations in the temperature gauge with it going to hot and then right back down to normal middle range while driving, in about 30 seconds. The first thing that came to mind was the thermostat, so I replaced that. Then, I got noise coming from my radiator fan so I ended up replacing that because the fan was wiggling and loose.

**Current issue + Pictures below**

Now, my car leaks about half a gallon of coolant a week and it's overheated 3 times but I've managed to pull her over and add coolant before it got too hot. I initially thought it was a head gasket leak and planned (still plan to) sell the vehicle as soon as I could buy a new one which is soon. However, if I can fix this problem, I'll keep her for a couple more months and save up for that higher trim in the new vehicle I want.

Me and my friend were burping the system and refilling the coolant since it got low again, and we noticed a mini puddle of coolant, almost under where the thermostat housing is. I first thought that maybe the thermostat seal wasn't done properly and it's leaking coolant from there, which perhaps it still is the case, but my friend insists it's coming from a gasket.

The below pictures are the best I could do at night and I'm hoping it sheds light on something whether it be bad or good news. The green circle is the "gasket" my friend thinks the coolant is leaking from. and the red circles are where I can see the coolant leak location from two angles. I'm hoping these pictures have some value in helping someone who knows this vehicle better than I do.

Also note: I do not have any foam coming out of the radiator cap nor is there any discoloration in the coolant. I also don't notice any performance loss or any discoloration of my oil.

Pictures below uploaded to Imgur.

https://i.imgur.com/4xqoUa0.jpg (Front View)

https://i.imgur.com/sxgpuii.jpg (Driver's side view)

Maybe that is the head gasket, but my friend insisted that the head gasket is located further down. I don't know. First time I'm actually able to provide pictures.

Sorry for the essay! I have a hard time not rambling.

Villiska

My friend is saying he thinks it's the "Plenum Gasket"

BabyGT

I'd guess tstat leaking as well

Villiska

As well as the Plenum gasket you mean? What exactly is the Plenum gasket? I've seen it sold online for $12 and the kit for $30 and my friend thinks he could replace it in a few hours. Is this easy to replace and easier to replace than the head gasket? I'd love to fix this issue and be able to sell my car for a lot more than what I can now.

BabyGT

No I mean I agree with you, I'd say its the tstat housing leaking.

BabyGT

From your pics and staring at my engine just now to get a feel for where its pooling.

PNYXPRESS

that looks like where the head bolts to the block. But, with that much coolant loss, it should be obvious where its leaking from.

Villiska

I just went outside now that it's light out and I don't see any coolant leaking from the housing itself, but I can peak in and see a little pool of coolant where it is in the pictures. It's really hard to look into that area though and I can't see to find where it's coming from.

I was just hoping there was like one obvious coolant holding area in that location that would point it out or something. Hmm.

Villiska

I'm assuming that is a very, very bad thing then?

Villiska

Also another thing, my backfill tank for my coolant doesn't go empty. Even though I have so little coolant that my car overheats, the backfill tank is leveled where it's supposed to be.

I've also replaced the radiator cap because it was like 8 bucks so that's new too.