'99 Taurus 3.0L OHV heat problem

Good morning, fellow enthusiasts! I am new to the forum as of yesterday, so please bare with me. Sure hope that I'm not violating any of the rules with this post, as it appears there is a redundant problem with the cooling systems on these Fords. I want to spell out this problem specifically so that I get some proper advice, as I hate to do repair work by going through the process of easter egging (replacing parts until you finally stumble accross the one that does the trick.) The Taurus that I am working on has been without heat since early this spring. Since then, the plastic tee in the heater core bypass line split, resulting in the entire hose system being replaced and the cooling system getting flushed out as part of the job, and a new thermostat was installed.......still no heat. Have disconnected all hoses and run water through heater core and hoses........no blockages found. The bypass hose gets good and hot when driving the car, but the hoses to/from the heater core do not. I pinched the bypass hose off with a clamp hoping to force coolant through the heater core but hoses still do not get hot. What is going on here? Are the fins on the water pump so eroded away that it cannot do its job? I've been told by the owner that the temp guage used to indicate just above the graduation near the bottom of the indication, but that it shows slightly below half way nowadays. Does anyone have any good advice? All responses will be greatly appreciated!
Thanks,
Rob

My parents I have a '99 Taurus with the 3.0L OHV with the same problem on heat. We have had the cooling system flushed twice do to the system being so dirty, the thermostat replaced, water pump replaced, radiator replaced, along with antifreeze overflow bottle replaced. Still had no heat. Took it to a shop and they couldnt find the problem, so we than took it to the local Ford dealer today, and they came its the bypass valve under the dash thats bad. After we get ours fixed I'll repost if it took care of the problem or not. Hope this helps.

I wasn't aware that there was a bypass valve under the dash, but I'll check with the Ford dealer. I've already checked to make sure that the blend door actuator under the dash is working properly, removed it from the blend door operator linkage to make sure that the door was operating properly and not stuck in one position or another. I beleive that I have eliminated all the problems in the interior of the car. The heater core nipples extend through the firewall into the engine compartment, so I'm not exactly sure where the bypass valve would be located. For that matter, I've looked at all the wiring diagrams and haven't seen any kind of control wiring for a bypass valve. Make sure the dealership isn't trying to snow you to run up some kind of huge bill. I will be looking forward to your response once you have gotten yours back with working heat. Thank you for responding!
Rob

After talking with my father on what exactly they told him when he picked it up, I was wrong. They call it a bypass kit, but its nothing more than flushing out the heater core. However after doing research myself, along with talking to a few mechanics, we've came to the conclusion that if we only flush it, it will most likely clog by next winter, so we're just going replace it. Sorry bout the confusion on that.

I had the same problem on my '97 Taurus 3.0 OHV for over a year with no heat. This started right after I had replaced the plastic degas bottle (overflow tank), flushed the system, and refilled the coolant. The heater core was blocked with sediment. When I felt the small angled hoses going into the firewall to the heater core, one would get hot much faster than the other (I believe it was the lower hose coming from the thermostat side of the engine). The other hose going to the water pump would eventually get hot, but it took a long time. So I disconnected the "H" hose on each side and fitted a garden hose remnant at each side with a female coupling. Then I ran the garden hose through each side back and forth a few times. The first flush from the water pump side (which I believe constituted a backflush) blew out all the crud (dark brown water). Subsequent flushes were fairly clear. I also have a problem with my blend door which I THINK is the actuator - which I've removed. There is a loud thumping noise whenever the temp knob is in a particular region of the dial. It sounds like the door is opening and then falling down. What I've done in the meantime is stick a small piece of thin 1" square plastic into the metal "banana" bracket on the face of the air box under the dash to permanently prop the door up to the heat position for the winter. Right now, everything is working fine. But, I've got to determine if the actuator is really the problem and reinstall a new one (~$45) if necessary.

If your bypass hose is HOT, then fluid HAS TO BE flowing toward the heater core. Maybe your metal tubes on the firewall are obstructed in some way, constricting the flow through the core. I've heard of this happening. Low flow is the same as no flow, and will result in no heat. This was my problem...

Well it isnt my car, and I'm not doing the work on it, so I can't say if it will or will not take care of the problem. Just going by what Ive been told. I can say this, what the heater does is give a good shot of hot air when you turn it on, than after running for 2-3 minutes it goes to cool air, instead of staying hot. However every once in a while, maybe one time out of every 25 times, the heat blows fairly good.

I've chased the metal tubing to the core with steel wire and have found no blockages. I've taken the hoses apart from every possible connection and am finding no blockages. This just doesn't make any sense. Is it possible that the system is air bound? Although I don't see how as I filled the core and hoses with coolant before reattaching everything.

I've chased the metal tubing to the core with steel wire and have found no blockages. I've taken the hoses apart from every possible connection and am finding no blockages. This just doesn't make any sense. Is it possible that the system is air bound? Although I don't see how as I filled the core and hoses with coolant before reattaching everything.

If your '99 is similar to my '97, it has a plastic coolant recovery tank with a pressurized cap that is self-purging - the system is constantly expelling air automatically. I would make absolutely certain that the heater core is not plugged (even partially). Hook up a couple of remnant hoses with female couplings and attach a garden hose alternately to each end. If this runs clear and without obstruction, then the system (somehow) isn't pumping fluid through that channel. But you have said that fluid IS flowing through the parallel hose, so that doesn't make any sense, because the "H" hose doesn't alter flow in any way - the fluid flows through both channels simultaneously. Maybe you should try hooking up a piece of thick clear (see-through) hose (off a roll at Home Depot or Lowe's) to watch the flow as the car is running. Maybe you'll find that your pump is barely pumping fluid (but if that were the case, you'd probably be seeing that on the temp guage).

Well my parents got their car Taurus back. Changing the heater core definately did the trick. Heats work as good as a new vehicle.

Well my parents got their car Taurus back. Changing the heater core definately did the trick. Heats work as good as a new vehicle.

If I were you, I'd ask for that old heater core - to make sure it absolutely needed to be replaced. My shop manuals clearly state that heater cores are very often needlessly replaced. If it wasn't leaking into the cabin area, then it was probably OK and just needed to be flushed. I wouldn't put it past some garages to simply flush the thing out (10 minutes work) and then bill for replacement (several hours and $$ hundreds $$)...

Well we had the dealer say it just needed a flushing, however after speaking with multiple people, we came to the conclusion that do to how dirty the cooling system was when we first bought the wagon, that the flush would probably only help for a little bit and by next winter, and probably sooner it would be right back in the same situation, so we choose to just replace it instead of flush it. However we did not have the dealer change it, we had a family friend who knows quite a bit about vehicles do the work on it, so we know that it is a new heater core and not someone just billing for a new one and than just flushing it out. However I agree with you and wouldn't put a past most shops to just flush out the heater core and claim the put a new one in.

Today the coolant temperature started rising while idling at a traffic light, then started to cool down somewhat once got going again. I'm almost certain now that the problem(the original problem at the beginning of this post) lies in the water pump. If the thermostat were stuck closed, there would be no circulation through the radiator to cool the engine down once moving again. It makes sense that the pump vanes are eroded to the point that coolant isn't flowing until a higher engine speed is reached, and then only just enough to have the temp hang around half scale and not enough to push coolant through the core. Thanks for everyone's comments. I will definitely use this forum again and will recommend it to everyone I know!

Today the coolant temperature started rising while idling at a traffic light, then started to cool down somewhat once got going again. I'm almost certain now that the problem(the original problem at the beginning of this post) lies in the water pump. If the thermostat were stuck closed, there would be no circulation through the radiator to cool the engine down once moving again. It makes sense that the pump vanes are eroded to the point that coolant isn't flowing until a higher engine speed is reached, and then only just enough to have the temp hang around half scale and not enough to push coolant through the core. Thanks for everyone's comments. I will definitely use this forum again and will recommend it to everyone I know!


Just changed out my heater core while having the same damn problem. I'm thinking like you..is it my water pump just not pumpng well enough. Let me know if your pump change out helps. Thanks