Can I repair a 1999 Ford Ranger,3.0 liter, 6 cylinder, Intake Manifold, two tubes leaking that connect to heater core hoses.

bypass heater hose

I can give you a couple of possible causes(1)freeze plugs in the block,there round & look like drink coasters,but are brass(2)intake manifold gasket can be leaking from the corners where water jackets are/also the head gasket both are on all four corners,I don't know what motor you have,but there are pipes that are called crossovers that run from the back off the timing cover to the heater core on the fire wall,sometimes on top of the manifold on one side & there will be a hose connected to it possible bad hose or corroded tube?

95 Lincoln town car coolant leak under intake SOLUTION EASY

Ok this is a 4" piece of hose leaking on a tube that runs under the intake manifold and fastens to the rear of the engine with 2 small bolts that are very hard to get to. The heater core hooks up to this tube with a 5/8 hose that's 3/4 on the other end going into the heatrer core.
Solution:
remove alternator
see clamp on hose?
remove it.
If you can't remove it, clamp vice grips on it and take a steak knife and cut through the hose towards the rear of the engine. Now with large screw driver pry the hose and clamp off the nub on the rear of the water pump housing. You may have to move the tube and remaining hose out of the way first. Just stick your hands in there and force it out of the way. Now you have a clean nub to hook a 5/8 bypass hose to. Here's where you get it. Go back to the heater core and and remove the hose that connects to this tube that runs under the intake. Just cut it where it hooks to the tube and remove it carefully from the heater core because this is now your needed bypass hose. Now with a couple feet of 3/4 hose and a coupler you have all you need to reroute this water outlet around the engine to the heater core. Take your hose you cut from the other end of the tube and removed from the heater core and and fasten it to the nub on water pump housing use new screw type stainless Steel clamps. You have to take this one apart to put it on. Stick a 3/4 coupler into the other end and route a long section of 3/4 hose under alternator to the heater core using SS clamps where needed. job done... Just leave the old tube where it is under the intake manifold......Thank you Very Much

Yes, there are expansion plugs (freeze plugs) on both sides of the engine block and at the rear of the engine block between the engine and transmission. There are also a couple in the ends of the cylinder heads.

With all that said, I would like to add that many times with that engine, the heater tube and connecting hoses can leak and be mistaken for a rear expansion plug leaking. I would definately check this before pulling the transmission out.

There is a tube that runs from the back of the water pump under the intake manifold and out the rear of the engine where it hooks up to the heater hose/heater core. This tube has a small hose connecting it to the back of the water pump. There is also a hole in the back of the engine block that will allow antifreeze from under the intake manifold to leak into the transmission bell housing area. When this tube or hose leaks, it often gets mistaken for a leaking rear expansion plug.

It is very easy to check for this. Remove the serpentine belt and remove the alternator and look under the intake manifold down in the "valley" between the cylinder heads. If there is antifreeze in there, the hose or the tube is leaking. Look at the picture below. Item #3 is the tube and hose assembly I am talking about. Usually, just the hose is leaking. It should be replaced with a short piece of SILICONE heater hose. On some of the vehicles, there are 2 hose clamps. On others, the end of the hose that is attached to the tube has a crimped collar on it. If yours is like this, you can fix it by carefully cutting the crimp collar off and replacing the hose using band clamps. (screw-type)

Also look for antifreeze leaking into this area from the front intake manifold runner. They tend to leak on the front runner near where the thermostat housing is located. These will also leak into the valley area and run out the back of the engine. If the manifold is leaking, chances are it is warped. DORMAN makes a replacement intake manifold kit just for this purpose because it has been so common. It is also very easy to check for this with the alternator removed.
The DORMAN part number for your vehicle is 615-178 (See second picture below)

the heater core is the only thing you havent replaced besides the thermostat so feel the carpets and floor around the floor heater out puts to see if there damp or sticky they may smell like a sweet smell as well.

1.Disconnect the cable from the nrgative battery terminal. Drain the cooling system
2.Remove the cowl vent panel, Then disconnect the heater hoses from the heater core inlet and outler tubes at the firewall.
3. on models so equipped, disconnect the engine ground strap attached to one of the heater core tubes.
4.Remove the center dash support trim and the radio cassette box ashtray.
5. Pull back the carpeting and pull the rear airflow duct away from the main floor duct.
6. Remove the two instrument panel support brackets and the heater main floor duct.
7. Remove the screws and the heater core cover, the remove the heater core. (Be careful not to tear the foam sealing material).
8. When reinstalling the heater core in the housing, make sure the original foam sealing the material is intact and in place.
9. The remainder of the installation is the reverse of removal.
10. Fill the cooling system.
Run the engine and check for coolant leaks.
Good Luck!!
Any questions please feel free to post it and I will answer it.

What kind of car?

From Haynes Repair Manual #36071, Ford Ranger Pickups 1993 - 2005: (1)Disarm the airbag system; (2)allow the cooling system to completely cool down; (3)using a thick cloth for protection, turn the radiator filler cap to the first stop; (4)step back and let the pressure release; (5)once the pressure has been released, completely drain the cooling system; (6) working within the engine compartment, loosen the ****,ps on the heater hoses at the engine compartment side of the firewall, twist the hoses and carefully sepseparate them from the heater core tubes; (7)plug or cap the heater core tubes to prevent coolant from spilling into the passenger compartment when the heater core is removed; (8)place a plastic sheet on the floor of the vehicle to prevent stains if the coolant spills; (9)remove the instrument panel; (10)remove the PCM heat sink and ground strap; (11)remove the heater plenum chamber; (12)separate the heater core from the heater plenum chamber; (13)installation is the reverse of the removal with the following additions; (a)fill the cooling system; (b)run the engine, check for leaks and test the heater.

It's one of the easiest cores to replace that I have encountered. Disconnect heater hoses at firewall. Probably doesn't matter about hose placement, but I always mark them just in case. To remove the fiber cover under dash, take a flat blade screwdriver and pry out the center pin of the expansion clips that hold it in place. There are four 5/16 head screws that hold the bottom/drain tray cover. Core will pull through the firewall and then down. You may have to silicone/glue or replace the foam seal strips on the new core. Before you install the core, check the distance between the inlet and outlet tubes to ensure they match the openings in the firewall. This saves time. It helps if you have someone on the outside to guide you when stabbing the tubes through the firewall. Replace bottom cover. You may have to hold one of the tubes when reinstalling the first hose to the core. Replace any lost coolant and check for leaks prior to reinstalling the fiber cover. If the cover seal is in good condition, any leak should drain through the firewall, otherwise it may leak inside cab. .