I have an 87 Ranger w/ 2.9l that is stuttering, bubbling into the radiator, and the overflow tank. It does this while running and after i turn off the engine. the amount of air bubbling increases if i lift up the radiator lever. I'm going to do a vacuum test and compression test this weekend.
A little back ground: 4 years ago it was doing the same thing, stuttering, and seamed to be miss firing. I was thinking i had blown a head gasket. No water found in the oil, no oil in the radiator. I didn't have the radiator pressure tested. Instead i bought a 98 Ranger for my daily drive to give me time to figure out what was wrong with my 87 Ranger.
I flushed the radiator with clean water numerous times to remove all antifreeze, then used K&W Block Seal. It stopped about 75% of the air bubbling, so after about a month, I repeated the process. All the air bubbling stopped. I only used the truck for very short trips (less than 1/2 a mile).
2 weeks ago i started driving it back and forth to work (35 miles one way). It ran great. No overheating, no bubbling, no stuttering. Then as I was driving to work, it blew a heater hose. I replaced the hose, refilled the radiator (using Prestone's back flushing system), put in a new 180 degree thermostat, and a new heat sending unit. It ran great for about 2 days. Now it is doing as discribed above.
I need to know how to tell if it is a blown head gasket cracked head (has never over heated) ,or an intake manifold gasket.

 

Dollars to donuts you have a cracked head or two. The amount of pressure you describe is in line with compression gas pushing into the cooling system. You can get a test done that checks for combustion gas in the coolant. You can get a pressure gauge and pump to pressurize the system cold, and then check for leakage into the cylinders.
I would go for the gas test. The 2.9 cracked it heads at will, no overheating necessary, if I have remembered correctly.
Have you pulled the plugs to inspect them for being 'washed' by coolant? You might be able to find out if a particular cylinder had a problem by inspecting them.

tom

 

If your heads are indeed cracked, you can purchase new aftermarket OEM replacement heads for about $350 for both heads that have thicker walls, so they don't crack.


I believe they are called "World" heads, at least on my 87, the engine bay is pretty open, and shouldn't be to much of a hassle to change out the heads.

 

Thankx for your responses. I won't really know until this weekend. I plan to inspect the spark plugs when I do the compression test. Then I plan on having the coolant tested for compression gas. Then I plan to start taking the engine apart. At least to check for blown head gaskets and cracks in the heads themselves. I hope the heads are ok, because the exhaust manifold bolts are really a bear to remove.

 

I'd just pull the heads, you'll do that for either a gasket job or heads anyway. Pull the heads and have them profesionally inspected for cracks (unless it's obvious), and look for signs of leakage in the gasket. It doesn't matter which problem you have, stop-leak won't fix it, and those heads are going to have to come off!

 

An update. I believe you are all right. I pulled the plugs and did a compression test today. First I had Bosch Platinum 2 plugs. cylinders #3 & #5 inside ceramic insulators were broken. All other plugs were normal. I used my shop vac in all cylinders, no antifreeze in cylinders.
Compression was high in all. 1=160,2=170,3=155,4=160,5=175,6=170.
Put in new stock plugs, new cap, rotor, and wires. Tomarrow I will back flush the radiator, and Monday I will go to a radiator shop to have the cooling system tested for compression gas. I don't have the money at this time to buy a gasket set, or to have the heads tested. I hope to limp this engine along for a few months and just put in a rebuilt one. Until then I will try some stuff called "Blue Devil engine and cooling sealant." They have a web page Universal Products, Inc. It is a blue liquid that you put into your radiator, after a system flush. It can be mixed with 50/50 antifreeze and water while the engine is cold and the thermostat removed. Then you run the engine for 50 minutes, let it cool down, then reinstall the thermostat. no need to flush after treatment.