1991 ford ranger 4.0 V6 antifreeze in exhaust

4.0 ranger antifreeze in exhaust
I have a 1991 ford ranger 4x4, 4.0 v6. 190,000 miles. Runs great and even gets 18-20 mpg on hwy trips with a 1200lb camper. I have been using small amounts of antifreeze for the passed year with no leaks. Lately much more, sometimes a 1/4 gallon in 400 miles. 4,000 miles ago was having a miss and changed the plugs that had 30,000 miles on them. Miss went away but came back 2000 miles later. Changed plugs again and wires and miss went away. Now about 1000 miles later no miss but using more antifreeze. The plugs each time looked pretty good. The last time, when I changed the plugs and wires, it started blowing a lot of white smoke on initial start up for at least 30 minutes at idle, then just water dripping off the tail pipe. It did that a few more times and then stopped. When it sits for a few days I can see the smoke on start up for a few minutes only. I just took a 400 mile trip with the camper and it ran great except for the using antifreeze. I took a compression test and they are all within 7 lbs of each other. I did a block test using the blue fluid in the proper tester to check for exhaust fumes in the air in the radiator. The fluid stayed blue indicating no exhaust fumes in the radiator. I hooked up a radiator pressure tester and pumped to 20 lbs, didn’t drop for 30 minutes. On a cold engine pumped radiator tester to 10 lbs, disengaged ignition and turned engine over 5 different times 10 seconds each. Needle stayed at 10 and didn’t fluctuate.

I hooked up a vacuum gauge, teed into the line from upper intake manifold to brake booster. I am at 5000 feet altitude so deducted 5 from all the results of the tests I read about online. Everything seems totally normal with vacuum. Needle is steady at 16 at idle, 17 steady at 1800 rpm and 2500 rpm. At 2500 rpm for 15 seconds and release throttle it climbs to 19 and then back to 16. If intake manifold gasket is leaking would it show up in vacuum test?
My first thoughts were head gasket but after reading some forums I am wondering if it could be intake manifold gaskets. I am not sure about the configuration of the water and intake ports. Seems like antifreeze is getting into the combustion but no combustion getting into the antifreeze.
I called Ford dealer and they said could be a thermostat housing or sensors around that area on the intake manifold or the water pump and of course wanted me to bring it in for testing. It does not make sense to me how any of those could cause leaking into the manifold? Does anyone know how that could happen and how to check for that?
So…Is there any way to know if the antifreeze is coming from either of the intake gaskets or the head gasket or a cracked head? If it was a cracked head or head gasket I was thinking of trying a sealer, steel seal. If a manifold maybe a product with copper in it. If that didn’t work then I was going to tear it down. Any advice would be appreciated.

Well, hope for the least expensive repair. I had a 1990 Ford Aerostar with the 4.0 V-6. I bought it used, but fortunately had the factory warranty. When I would first start the engine, it would idle roughly for about a minute and then smooth out. The dealer diagnosed it as a bad head gasket which was replaced. A year later, the problem came back and it really started missing. When the engine was stripped down, there was a crack in a cylinder head. Enough coolant had leaked into a cylinder to score the cylinder wall. The entire engine was then replaced, fortunately still on warranty.
My guess is that at the minimum you have a blown head gasket.

I am leaning towards leaking lower intake gaskets

It sounds like you’ve done a pretty good diagnosis to this point. You could take off the intake manifold/throttle body and look for something suspicious I suppose. On my early 90’s Corolla a there is a cooling pipe that goes to the throttle body, which is used to measure the temp of the coolant and there’s a thermo-wax gadget there that increases the idle speed when the coolant is cold. On newer cars this is done differently, using the ECM and and idle air control device (IAC), but since your car is a similar vintage to mine, maybe it works the same way, and that part is leaking into the intake manifold for some reason.

If this were my car I’d do some investigations and research of the car’s shop manual or whatever is available to you, see if there is a coolant line going into the throttle body/intake manifold area for idle speed control.

I suggest removing the upper and lower intake manifold for inspection.

If the intake gaskets appear to have split, it should be fairly obvious at this point.

If they are split, I wouldn’t worry too much about the head gaskets at this point.

While failed head gaskets are a possibility, you’d have to remove the intake manifold anyways . . .

I’ve experienced a similar problem with my '99 Ford Ranger 4.0L. It started with a slight misfire in #4 cylinder (per OBDII) when I first start in the morning and then goes away. I checked the #4 plug and it seemed OK. I took it to a “reputable” repair shop and all I got was a run around convincing me to change this and that. So I went to a Pep Boys mechanic I knew and he suspected one or more “hairline cracks” in one or both heads, and the reason why I goes away was that when the engine warms up the crack tightens up due to temperature. He also said that the problem (hairline cracks) is predominant specially with Ford heads. I was skeptical at first but as I continued to drive the vehicle, I started to notice slight white smoke and signs of emulsification around the oil fill cap. Well I ended up with both heads being replaced. I inspected the old heads and saw where they marked them after the magnaflux. One crack was in the #4 cylinder area. Just thought I might throw this in as a possibility.

If enough coolant has accumulated in the crankcase to cause the oil to look like a chocolate milk shake and the source is at the head, whether cracks or the gasket or the intake, the coolant would have passed the rings on one or more cylinders and it would be extremely likely that those cylinders would soon become galled unless the pistons were removed and cleaned.


With all due respect, I doubt anybody’s going to be removing pistons for cleaning on this old truck

It doesn’t seem worth the expense and effort

It wouldn’t seem worth the effort to me, either, @db4690.