Bronco II 2.9 V6 FI

[JDGlenn]

It's late at night and I should be in bed, but I can't get to sleep because this thing is driving me crazy. Two weeks ago, I pulled a trailer to Tiajuana with my Brondo II. It's a 4x4 with a 3in. lift, air suspension system, custom paint, custom driveline, new clutch, new brakes, new interior. I've worked the whole thing over. Here's what happened.

One the way home everything was fine until I hit Prim Nevada. We stopped at Prim and spent the night. The next day was 108 degrees and as soon as we left the darn thing started overheating. I kept pulling over to let it cool down and it just kept getting worse. At one point, I stopped to let it cool down. The water was boiling and I reached down to check the fan clutch (it's a thermostatic switch, so it should have been locked). I grabbed the fan and it spun free. I thought, O.K. it's just the fan clutch. We limped into St. George, I put a new, larger, variable pitch fan in and did completely away with the fan clutch. Pulled out of town and it immediately started overheating. I got about 20 miles and the radiator blew out. A friend came and towed my outfit to his house near Cedar City. We put a new radiator in it--I used the one for an automatic, even though mine is a standard--so I could have more coolant capacity. We got it all back together the next day and I started out again and it was still overheating. I had replaced the thermostat before I left. The water pump is only a year old. It has a new radiator cap. When we got home a friend of mine said that it was probably a hairline crack in the head gasket, even though there wasn't any visible sign of oil in the water.

We replaced the head gaskets and I had the heads shaved--it took 8/1000 to true them up. We put everything back together and the engine purrs, but it still overheats. I'm going crazy. I'm going to put a new thermostat in, just in case the old one got srewed up when the engine was overheating. I hear that this engine had some real problems with the heads. Could there be craks, even when there isn't any visible sign of transfer of oil and water?

Any other suggestions about how to fix this? I'm thinking of wiring up an electric auxilliary fan for the thing.

Help.

 

[Justshootme84]

An old trick I use is to leave the thermostat out, and fire up the motor. If it still overheats, you can rule that out. Might also want to backflush the whole system, including the heater core. Which engine do you have?

 

[CraigK]

JDGlenn

Just my thoughts for free, and worth every penny . . .

Interesting problem.

ASSUME-ing you have the fan issue fixed, and it is circulating air through your radiator . . .

You have lots of radiator capacity, and air going through the rad to transfer heat out.

But the motor keeps overheating.

So . . .

Either the motor is making WAY too much heat, or heat isn't transferring to the radiator properly.

If the motor is making WAY too much heat, (i.e. no/low/bad oil, one or more cylinders running with lean/no fuel, bearings shot - metal to metal etc.) I think you would notice it in how the motor runs, or stops running.

(If a cracked head or block, you would see a problem with the coolant: discoloration, losing fluid, emulsion in the oil, steam in the exhaust etc.?????)

But you don't report that.

So . . .

The engine is probably not transferring heat from the engine to the radiator . . . .

Why?????

Coolant Blockage?

Bad Coolant Pump?

Just because the pump is a year old doesn't mean it's working properly. (My new alternator lasted 102 days!)

Also, the problem came on suddenly, and is severe. Like the impeller on the pump is no longer connected to the pump shaft? Or the impeller vanes are plugged up? Or that a coolant gallery suddenly became plugged with something that broke loose?

A possible scenario: The motor was running fairly hot for an extended time period. The impeller to shaft grip/clearance lossened with excessive heating and cooling. When you restarted the next morning, the impeller was no longer spinning with the shaft. Good radiator, good coolant, good motor, just not enough movement of coolant from the block to the radiator.

Whaddya think?

It's such an easy and relatively inexpensive job to remove and replace the water pump that I wouldn't think twice about my next move. And while the pump is off, check the coolant galleries as best you can. And replace the temperature sensor for good measure?

Again, just my thoughts . . .

GOOD LUCK!

CraigK

 

[JDGlenn]

Craig, thanks for the advice. I now remember the guy at the machine shop telling me to bypass the heater core to make certain that it hadn't gotten completely plugged when the system started boiling. About half the water ports in the block were plugged with gunk when I pulled the heads. Also, the scenario with the water pump is a very real possability. I'm going to try the less expensive fixes first. The engine runs great and sounds great--no missing. I just have to use premium gas with the heads shaved ;-) There's also no top end clatter. All in all, the engine sounds strong. I really can't believe it's a cracked head. I'll bypass the heater core tonight and see what happens.

Jim

 

[JDGlenn]

An old trick I use is to leave the thermostat out, and fire up the motor. If it still overheats, you can rule that out. Might also want to backflush the whole system, including the heater core. Which engine do you have?

It's the Cologne 2.9 V6. I'm going to bypass the heater core tonight and see what happens. Also, it sounds like the water pump may be bad as well. Friday, I'll have more time and probably will pull out the thermostat for a check. The more I think about this, the more it sounds like a heat transfer issue and not an engine meltdown.j

Jim

 

[JDGlenn]

Update, I bypassed the heater core last night. It seemed to help a little bit, but the engine is still running hot (still in the top end of the temperature gague). It really drives it up fast if I turn on the AC--obviously putting more stress on the engine. I'm going to take out the thermostat and check the water pump tomorrow. If nothing changes, what's next? I drained a little oil out to see if there was any water in it--water and oil don't mix...right? There is no visible sign of anything in the oil. It looks clean and I can't see any water droplets. Same with the water jacket. There is no oil sheen on the water that's circulating in the radiator. It just seems to get hot very fast and stay that way. I ran a test today. I drove to catch the train to work (25 miles). I want to see if I stress the engine if the water and oil still stay clean. We'll see tonight when I get home.

Jim

 

[89Bronco58]

take the thermostat out completely, reassemble and run the truck, see if it over heats, if it does, you need a waterpump or you have a serious block somewhere

 

[jaminjimlp]

is that radiator new or used.... i have a bII 89 w/2.9 v6 but on my s10 i had a similar problem and it was driving me nuts i tried allot of things as well but one day i though maybe the radiator is clogged up so soon as i got a chance i pulled it out and took it to a radiator shop and had it "rodded out" this is where they remove both sides or top and bottom and run a rod through each coil tube and wa-la it when from 260 deg. to 190 deg. which is what the t-stat is.....

let us know the out come.

oh you may want to put a fan clutch back on... it will save you some gas money.

 

[andre]

Q... auto or manual tranmisiom

IF automatic check oil if u did not over heat tranmision

let it idle check temp got around the block 2 or 3 time check temp