1986 F250 Diesel, 6.9, white smoke/haze/fog coming out vents and dash.
 

Hello everyone,

My Dad has just given me our family truck. A 1986 F250 Diesel with the IDI 6.9L diesel motor. It runs AWESOME.

I'll start with everything I know, as I realize what may seem irrelevant to me could indeed be relevant.


I took ownership of this truck on Friday. My dad has owned this truck since 2004, and it's been a great runner, but it's only ever received the very bare minimum of maintenance. This truck has been driven less than 5k miles in the last 5 years.

Yesterday on Saturday, I drove it 100 miles. It runs awesome, and ran great for the first 50miles at 60mph on the freeway. When I got where I was going, I checked the oil, and coolant. Oil looked very clean, but was very slightly over full. Coolant overflow tank was completely empty. I had kept an eye on the temp gauge the entire time, and it never got much passed the middle. I bought coolant and filled it up at the radiator until it was full. My dad had told me that the truck leaks coolant, but not how much. I had failed to check the coolant before I left.

On the way back home, I lost the alternator belt on the freeway at 60mph. It disintegrated itself and knocked the power steering belt and A/C belt off simultaneously. I pulled over instantly. I was able to get the fan belt and power steering belt back on without much hassle, but the alternator belt, which in turn drives the vacuum belt, was gone. I drove it home on battery power for 35 miles. No big deal. The brakes were manual, without the vacuum pump being powered, and the truck shifted late/hard as well.

I bought new belts the same day, and installed them. Perfect, back in business. Brakes are great, truck shifts great.

This morning, I decided to give it another test drive, 10 miles to my buddies house. Within a few miles, I started getting a hazy fog coming out of the passenger side vents, and leaking out under the dash. It was fogging up the glass. I pulled over, popped the hood, but could see where it could be coming from.

I drove it 5 more miles at 35mph while the problem persisted, and parked it for 5 hours. Drove it 3 miles to a fathers day get together, and the haze/fog was present nearly immediately. Parked it for 5 more hours.

Now, I had to drive home 10 miles. Nearly immediately the fog/haze is presently coming out the vent/dash. Only on the passenger side of the vehicle. It is much more present under acceleration, and calmer while cruising, less present during idle but still noticeable.

Then I notice a wet blotch in the footwell of the passenger seat. The carpet is wet. I touch it, and the liquid is slippery. I taste it, and it tastes like coolant.

I notice that the exhaust pipe is also smoking a bit at idle (when up to temp), and bit while under acceleration as well.

What are your best guesses for the cause of my problem?

Any advice on where to start to fix this problem? All my research says it's the Heater core? Easy enough fix in the old '86 6.9 Diesel?

Thanks in advance!

Here is a video of the issue.

That usually means the heater core is leaking. The fog is coolant mixed with the air blowing on your windshield.

One nice thing about our old trucks - the heater core is extremely easy to replace.

Welcome to FTE! Your problem is a leaking heater core. If you are lucky and have the standard factory-installed HVAC system it is an easy fix:

1. Lower the coolant level, and since this truck hasn't had good maintenance I'd go ahead and drain it.
2. Pull the heater hoses off the heater core at the firewall. But again, with minimal maintenance I'd look the hoses over closely and unless they look new I'd replace them as the hose is sold in bulk and is not expensive.
3. Lower the glovebox door and remove the liner.
4. Remove the 8 to 10 screws holding the cover over the heater core
5. Remove/replace the heater core. But while in there see if there are puddles of coolant you can dry up, or anything else that doesn't belong there.
6. Replace everything, including the heater hoses, but leave the firewall end of one hose off. That's because that is the high spot in the cooling system and by leaving it open until coolant starts coming out you'll get the air out of the system easily. So, with the hose kept higher than the fitting, fill the system until coolant starts coming out the fitting, and then make the connection.

How in the world are we supposed to work with a detailed post like this? You've included relevant details of the truck's history, precise observations, what you've done, etc. We are more accustomed to working from queries like this:

"Yo, AlDog here. Wazzup? Got this mist inside my truck. What can it be? My bud'z cousin worked on a truck wunce and sez its water pump. IDK."

Repeated infractions of forum protocol like that may result in firm disciplinary action, up to and including promotion to moderator. ;)

All seriousness aside, after you replace the heater core, make sure to pressure test the radiator cap. The cap is the pressure relief for the cooling system. If not releasing as designed, it may have let the pressure build too high until something else let go, the heater core in this case.

If you don't have access to a pressure tester, at the very minimum I'd suggest replacing the cap with a new name brand one.

Well said, KR. Notice my detailed response? That has a lot to do with the detailed question. :-X22

I'll try to help almost anyone, but someone who takes the time to set out the background in a way that makes my job easy gets more time than AlDog. :)

Brilliant! Sounds like I should be able to tackle this this afternoon. Thank you very much for the detailed procedure list. Very much appreciated!

Good point on the radiator cap. It's the original. Sure as hell looks like it anyway!
I'll replace it with a new brand name one. Any brands suggested?

I've learned in the past to include any details I can think of, so the powers that be can help me help myself! I appreciate a good learning opportunity!

Whatever you do, do NOT buy a Mr Gasket cap - or anything else that says Mr Gasket. Their stuff has turned to junk.

I recently had a Mr Gasket radiator cap that wouldn't hold pressure and allowed the coolant to flow into the recovery bottle and then overflow it. I was standing in line at the parts store to get a new cap and was holding the old one. The guy behind me in line asked if it was a Mr Gasket, and then proceeded to explain that he has several with the same problem. He suggested I put a square on it and we discovered that the flange the held the seal against the radiator's neck was installed at an angle - and that's exactly the problem he'd seen. According to him, Mr Gasket said "It happens." :-hair

Thanks everyone! I was able to get the heater core replaced without much issue, drained and replaced the coolant, and replaced the radiator cap at the same time.

No more noxious fumes in the cab or nasty coolant leaks.

Thanks!

Congrat's! Good job. :-X22