88 Bronco II Won’t Start

[franklin2]

You still have air in it. Taking the heater hose off at the firewall will help but be super careful there, it's very easy to make the heater core leak. Don't twist and pull too hard on it to get it loose.

 

[Mhfco6]

Removing calipers this morning and smelled coolant, then noticed it dripping off frame rail on passenger side, below the heater core. Think it’s got a leak?

Going to work on this and fill heater core lines as described after brake job.

 

[franklin2]

Removing calipers this morning and smelled coolant, then noticed it dripping off frame rail on passenger side, below the heater core. Think it’s got a leak?

Going to work on this and fill heater core lines as described after brake job.

Just to be sure you understand, you are filling the engine with coolant via the heater core lines. The heater core will have some air in it, as will the rest of the engine. You can't get it all out, it will still have to be burped some. But filling the engine behind the thermostat (that is what pouring coolant down the heater core lines does) will get more coolant in the engine block.

Just run it with the radiator cap off, till the top radiator hose is hot and you can look down the radiator and see coolant flowing by. Top the radiator off, fill the overflow bottle half-way, and then put the cap on. After driving it a couple of days, check the overflow bottle, it should be a little lower than it was.

You will get some surging of coolant out of the radiator and some overflow, that is just air making it's way out as the engine heats up and the thermostat opens. You have already went through one episode of overflow, so the worst is behind you. Unless you open the engine up again.

 

[RonD]

You don't need to add coolant to heater hoses, and shouldn't
Just take one hose off at the firewall, and fill at radiator cap opening until coolant comes out the hose and open core port, then put hose back on, and a little air when you do that is not a problem at all
You are letting the air out of the engine part of the cooling system that is stuck behind the closed thermostat

Heater hoses/core are on the engine side of thermostat, and a high point, so as you fill at radiator cap opening the coolant will flow into the engine via the OPEN LOWER radiator hose, pushing the air up and out of the heater hose/core port
Without an escape the air is stuck in upper head when you fill it without removing the hose
And that can cause an "air dam" when you start the engine, water pump can't force the air out because thermostat is not open yet
So you can get overheating

Its just physics, give the air a chance to escape and it will take it, lol

Also its a good time to reverse heater hoses at the firewall, this reverses the coolant flow thru the heater core, back flush, and will keep it cleaner so it lasts longer

 

[Mhfco6]

I’m going to try all these tricks after lunch. I installed new calipers and brakes are fantastic. Topped radiator off with water and took 3x as long to over heat vs yesterday. 7 miles vs 21 miles. I’ll let you know how it goes.

I had some AutoZone reward points so grabbed a new heater core if needed.

 

[franklin2]

Follow Ron D's advice of just taking the heater core hose off, but filling from the radiator. You have a 2.9 which has the more conventional thermostat on top of the engine. I was thinking of my 2.8, which has the thermostat on the bottom radiator hose, and you have to fill the block via the heater core lines. Sorry about that.

 

[Mhfco6]

Okay, just removed a heater hose and filled radiator till coolant appeared pushing through at the firewall. Started engine with radiator cap off and started to notice the coolant flowing by around the same time upper hose was warm. I topped off the radiator and filled the overflow 1/2 up. I’ll keep you guys posted.

By the way, if you guys aren’t getting paid for all the fast and factual information .. you should be. Let me know who I need to talk to!

 

[Eddo Rogue]

it took a lot of "burping" the coolant on my 4.0 to get all the air out after the waterpump swap.

 

[RobbieD]

I had some AutoZone reward points so grabbed a new heater core if needed.

If you do replace the heater core, it's not much more money to buy about 6 to 8 feet of 5/8" heater hose, and just replace both of those with new. Check your hose clamps, too, and spring for new good ones if/where needed.

 

[Mhfco6]

I let it idle for 1 hour and it never left the “A” in NORMAL. Then I took it for a 6 mile spirited drive and it was in between the “O” and “R” in NORMAL when I parked it. But not bubbling.

Getting better, probably just needs burped a bit. Could be all the gunk in the system. When I had the water pump off I held a hoseon left and right side of the block for about 5 minutes each before it turned clear. Honestly it’s like a muddy brown now. Anyone ever used a flushing chemical with the thermostat removed?

 

[franklin2]

I let it idle for 1 hour and it never left the “A” in NORMAL. Then I took it for a 6 mile spirited drive and it was in between the “O” and “R” in NORMAL when I parked it. But not bubbling.

Getting better, probably just needs burped a bit. Could be all the gunk in the system. When I had the water pump off I held a hoseon left and right side of the block for about 5 minutes each before it turned clear. Honestly it’s like a muddy brown now. Anyone ever used a flushing chemical with the thermostat removed?

I hate the factory gauges. A lot of money and time is wasted looking at the factory gauge and trying to decipher if it's correct and what it's telling you. I always use aftermarket mechanical gauges on cars and trucks I care about. I have a mechanical oil pressure and water temp gauge on my Bronco II, and I know what the temp and oil pressure is exactly.

 

[RonD]

If temp was higher at idle, then went down when driving the fan is the issue

The fan's sole purpose is to pull air thru radiator when stopped or moving slowly
When driving, the speed of the vehicle forces air thru radiator, no fan needed

Fan clutch operates based on Radiator temp, on its front is a bi-metal spring that is heated up by warm/hot coolant flowing thru the Center of the radiator
As the spring warms up it expands, uncoils, which closes valves inside the clutch
Inside the clutch is oil
The water pump pulley spins the shaft inside the clutch, if valves are open the fan will spin but not at the same speed/rpm of the pulley and won't pull in much air
As radiator heats up valves start to close and fan pulls in more air and then more air, based on Center of radiator's temp as it warmed up

Simple test for fan clutch
Cold engine, sitting more than 5 hours
Open hood and try to spin fan, should be hard to spin, barely moves, this is called "cold lock" because oil is cold

Start engine, should HEAR the fan moving air because its Cold Locked, but within 5 to 10 seconds it should quiet down, its now unlocked, free spinning
Shut off engine
Spin fan again, should be easy to spin, unlocked
If cold lock and unlocked spin the same the clutch is bad, most likely

But go about your daily driving, and when you get home, engine and rad warmed up, shut off engine and spin fan again
Should not spin easily, warm locked
If its easy to spin replace fan clutch
BUT............first test radiator, remove the 2 bolts at top of shroud, and move shroud back
Run your hand over radiator fins, should be warmer towards upper rad hose then get cooler as you get closer to lower rad hose, and NO COLD SPOTS, you will feel cold spots
If center of rad is cold then clutch may be OK, radiator is the issue, blocked tubes in the center

If you do not have a shroud, then that's the problem, get one
Shroud allows a working fan to pull air THRU the radiator instead of from the sides
So same symptom as a bad fan clutch BUT the clutch would test as OK

Manuals and automatics used different shrouds, because manuals often use single core radiators and autos always used dual core
So shrouds are different depths

 

[Mhfco6]

If temp was higher at idle, then went down when driving the fan is the issue

The fan's sole purpose is to pull air thru radiator when stopped or moving slowly
When driving, the speed of the vehicle forces air thru radiator, no fan needed

Fan clutch operates based on Radiator temp, on its front is a bi-metal spring that is heated up by warm/hot coolant flowing thru the Center of the radiator
As the spring warms up it expands, uncoils, which closes valves inside the clutch
Inside the clutch is oil
The water pump pulley spins the shaft inside the clutch, if valves are open the fan will spin but not at the same speed/rpm of the pulley and won't pull in much air
As radiator heats up valves start to close and fan pulls in more air and then more air, based on Center of radiator's temp as it warmed up

Simple test for fan clutch
Cold engine, sitting more than 5 hours
Open hood and try to spin fan, should be hard to spin, barely moves, this is called "cold lock" because oil is cold

Start engine, should HEAR the fan moving air because its Cold Locked, but within 5 to 10 seconds it should quiet down, its now unlocked, free spinning
Shut off engine
Spin fan again, should be easy to spin, unlocked
If cold lock and unlocked spin the same the clutch is bad, most likely

But go about your daily driving, and when you get home, engine and rad warmed up, shut off engine and spin fan again
Should not spin easily, warm locked
If its easy to spin replace fan clutch
BUT............first test radiator, remove the 2 bolts at top of shroud, and move shroud back
Run your hand over radiator fins, should be warmer towards upper rad hose then get cooler as you get closer to lower rad hose, and NO COLD SPOTS, you will feel cold spots
If center of rad is cold then clutch may be OK, radiator is the issue, blocked tubes in the center

If you do not have a shroud, then that's the problem, get one
Shroud allows a working fan to pull air THRU the radiator instead of from the sides
So same symptom as a bad fan clutch BUT the clutch would test as OK

Manuals and automatics used different shrouds, because manuals often use single core radiators and autos always used dual core
So shrouds are different depths

The temp was cooler when idling, then crept up while driving. I remember when changing the water pump and removing/installing fan on cold engine the fan spun easily. I do have an auto with proper auto fan shroud. After put back together and short drive I noticed PS leaking so removed fan and PS belt, again while warm the fan moved easily. I’ll check the fins for cold spots this week.

 

[RonD]

??

I let it idle for 1 hour and it never left the “A” in NORMAL. Then I took it for a 6 mile spirited drive and it was in between the “O” and “R” in NORMAL

In most vehicles "N" would be colder than "L" but I assume 1988 gauge is opposite, lol

i.e. : https://www.f150forum.com/attachments/f10/495272d1501275376-engine-temp-gauge-not-working-correctly-img_20151108_073009_771_zps9vykci5m.jpg

or : https://i.ebayimg.com/images/g/xxQAAOSweetijmCm/s-l1600.jpg

Thats why its better to use 1/4, 1/3, 1/2, 2/3 and 3/4, lol

 

[Mhfco6]

I ran some Prestone cleaner in it, drained then ran/drain 3 times already.. still brown but getting better. I’m going to get more distilled water tomorrow and do it a few more times. The first drain was like mud with sandy bits. After I’m done with that I’ll let you know how it’s doing.