Help! Troubleshooting extreme coolant leak. Water pump or head gasket?

ant.96xlt · #1 01-15-2015, 11:38 AM

Hi all! Long time lurker, first time poster here.

Here's a shortened version of my question: Truck has symptoms of water pump failure and/ or head gasket/ cracked block. Need advice for next steps.

Backstory:

I bought a 96 xlt 4.0L V6 four months ago. Ran sluggish and started shooting misfire codes soon after on the highway (shaking at >45mph). Most of my driving is in town so I watched engine temp and minimized loads.

First, when addressing the misfire issue: changed out plugs, wires, oil/ filter and cleaned MAFS. The two hardest to reach plugs on passenger side (closest to firewall) were different brands and seized, so I don't know the last time they've been changed out. Had them soak with PB blaster to get them out. Runs like a dream when warm.

However, I run through a TON of coolant. There's never anything in the overflow tank and I top off the radiator every few days now. I don't have puddles..yet, but there is white smoke at start up. I was concerned it was a blown head gasket, but the test was negative when I used a uview combustive gases test on the radiator.

I'm thinking it may be a failing water pump since I do have a bit of a squealing noise at start up too. I'm curious if there's anything else I can do to rule out an issue with the block/ head gasket before throwing more money and parts at it.

I'm not a mechanic, but know I can fix the problem with the right direction.

I've also attached a pic showing the extent of the leak underneath the truck.

Anything else I should check to rule out a bigger engine block problem?

Thanks!

Ant in Oakland

smokinAMD · #2 01-15-2015, 12:52 PM

Step one....pressure test the cooling system.

Step two....your running like a dream when warm (you didn't say how it ran while cold....I'd assume poorly), and your mystery coolant issue on a 4.0 OHV, I'd suspect you have a failed lower intake manifold gasket. Start the truck up and let it idle while cold and spray around the lower intake with some carb cleaner. Bet you a nickel it's going to rev up on you and you'll be able to confirm an intake gasket leak.

ant.96xlt · #3 01-15-2015, 04:29 PM

Quote:

Originally Posted by smokinAMD

Step one....pressure test the cooling system.

Step two....your running like a dream when warm (you didn't say how it ran while cold....I'd assume poorly), and your mystery coolant issue on a 4.0 OHV, I'd suspect you have a failed lower intake manifold gasket. Start the truck up and let it idle while cold and spray around the lower intake with some carb cleaner. Bet you a nickel it's going to rev up on you and you'll be able to confirm an intake gasket leak.

Yeah, I was wondering about the pressure test because when I was doing the uview test the bulb wouldn't automatically inflate until I released the pressure of the tester seated in the radiator neck.

I'm also not seeing any water/ coolant in the oil. No milky oil or scummy oil cap.

It runs like a dream when warm now compared to how it was with the misfire code pre-wire/ plug replacement. Now when cold start it may hesitate and die until I step on the throttle some, but that's only intermittently and not every time I turn it over. It doesn't always puff white smoke at start up either.

ant.96xlt · #4 01-19-2015, 10:02 AM

Quick update:

I rented a coolant system pressure tester from Autozone, only to have to return 3 times to try to get the correct radiator cap adapter. With no luck. Going to head back today, so hopefully 4th time is the charm.

The ranger has started spewing more white steam and water out the exhaust, but no water mixing in the oil...yet.

I'm planning on switching out gaskets this week. Thinking of just focusing on manifold gaskets and not taking it down to the head gasket. I figure while I've got everything out and apart I should try to fix up as much as I can. Anything else I should check while I'm in there?

I'm attaching a new picture from yesterday. This is the main spot where I've noticed coolant leaking.

Thanks for the help!

cowboybilly9mile · #5 01-19-2015, 10:28 AM

The reason it "runs like a dream when warm", and presumably misses when cold, is because heat eventually drives off the moisture and the cyl(s) that miss now fire.

The early 90's OHV 4.0's were infamous for developing lower intake leaks (typically vacuum and subsequently, engine knock, sometimes slow coolant consumption) as noted; often times people were simply able to retorque the lower intake and cure the problem without replacement. Considering it takes about 30 minutes and is just a matter of your time, I would suggest trying this; don't be surprised if a couple bolts are finger tight. Also, there's one bolt in particular in back (maybe a few others) that is most easily tightened if you have a couple of swivels at your disposal.