Can I bypass the heater core to lower H20 temps??

jaymac · Mar 18, 2006

My synopsis is:
Temps rise to 195ish on the highway, and usually stay around 180 on the streets. Michael Yount suggested it was a flow problem, either rad. or jeater core.
As I have no heat (warm, but def. not hot), I think it's a clogged up H/C anyway. I flushed it last year and it helped, and temps also dropped. Then this past winter I flushed it again, but teh heat still didn't really come back. I'll replace it at some point, but for now, do you think bypassing it might lower highway temps, if indeed that is my "restriction"?
thanks~
J

timewarped1972 · Mar 18, 2006

have you tried flushing the entire sytem??

i would think by flushing the heater core you could tell by how much water coming out if it's clogged or not.

you could always buy a replacement core now, see how it flows ( with out installing it) then try it with your old one so you know if it's putting out the same amount of water....

there's also a flow resrictor in one of those lines, or i think it's from the intake manifold, a heater core restrictor, might want to check that too....

jaymac · Mar 18, 2006

I've since replaced both hoses from the water tubes to the core, so I think the restrictors are gone...
The water seems to flow OK thru the core, and I have flushed the whole system, so I'm kind of at a loss...

Tonys96Cobra · Mar 18, 2006

If it is clogged, then bypassing it will help. Give her a shot and see how it runs.

timewarped1972 · Mar 18, 2006

hmmmmmmm, so the heater doesnt get hot enough....but, it runs cool on the streets in stop and go but not on the highway??

are you using an aftermarked temp guage??

jaymac · Mar 19, 2006

yeah it's a sunpro; not the best, but accurate, as when it has overheated due to low coolant from a broken bolt, it's been right in in alerting me...

bobcatv8 · Mar 19, 2006

Is your lower air deflector still there and in good shape? The one on the bottom of the radiator support.
I had the exact same highway heat-up, city drive cool down symptoms when I stuck the 302 in my Bobcat wagon. I had tossed out the factory deflector during the swap. Bad idea. I reinstalled a cut down Crown Vic deflector and instant problem solved!

craigwhite89gt · Mar 19, 2006

its easy enough to bypass it and run around and see what happens. then you will know for sure if its the core or not.

jaymac · Mar 19, 2006

yeah, it's still there. Good shap? I don't know... It's a little wavy and ugly, but not cracked or broken...

90mustangGT · Mar 19, 2006

A certian amount of coolant goes through the heater core, but then runs to the t-stat area. If the heater core was clogged, the water would just flow past it, it would not effect cooling efficiency. However the ECT sensor is located in heater coolant lines, therefore a restriction might effect it's accuracy, but the temp gauge gets it signal from the other side of the intake, so it would not be effected. So bypassing/blocking the heater core will not effect cooling very much.

Is the air deflector, the rubber strip under the bumper on the radiator support, still there?

What radiator are you running? The stock one is really for a 4 banger, and hardly enough when it's new, give it (how old the car is) and due to deposits it just doesn't cut it. Really, the temps your seeing arn't that bad.

Be sure there isn't any noise comming from the waterpump area, that would indicated broken vanes.

Be sure there isn't air/gas in the system, either due to a leak, external or internal. I doubt you have a head gasket problem or you would see much higher temps.

Tonys96Cobra · Mar 19, 2006

Are you sure the HC doesnt affect cooling? Ive had two go bad on me throughout the years, and both times the car would overheat. After replacing the HC, it was all better

jaymac · Mar 19, 2006

Well, water pump is new. Rad was replaced as well, but you're right, it's the 4 cyl. unit.
Deflector is still there.
I do have a coolant leak from a broken water pump bolt, so there are air pockets from time to time. Today I took a hour and a half drive 2 ways on the highway, from 65-80 mph, and the temp gauge never went above 180*.
I also moved the gauge yesterday and changed grounds. It might've given it a more reliable reading...

soylentgreen · Mar 19, 2006

I would think that bypassing the heater core would have the opposite effect as the one you're after...if even noticeable at all. The heater core is like a little radiator. Having it in the circuit should help the engine lose heat...even when the heater is not on.

How about the radiator fan clutch? If it is stuck, it would turn a lot and cool hte engine on the side streets. But, on the highway, it might hamper natural airflow at high speeds.

soylentgreen · Mar 19, 2006

BTW...If bypassing the heater core is something you're going to do, you'll need to make a little U-shaped hose. However, the two metal tubes you need to connect to are different sizes. I assume Ford did this so that it would be obvious if you were putting the hose on the wrong tube. Anway...since I have done this before (bypassing the heater core DOES stop heater core leaks...lol), you'll need to fabricate the U-shaped hose with two different sizes. I used a couple of pieces I got from NAPA with a plastic coupler.

I guess you could bypass it at the front of the motor too.

90mustangGT · Mar 19, 2006

One thing I forgot to add is that the heater not working or not working well can also be the result of a controll cable or blend door failure.

Tonys89GT said:
Are you sure the HC doesnt affect cooling? Ive had two go bad on me throughout the years, and both times the car would overheat. After replacing the HC, it was all better

Low coolant will cause a overheat. When a heater core faile, it is usually leaking. Sometimes you get lucky and it leaks out of the A/C drain, and sometimes it soaks the carpet and that odor is hard to get you, but anyways, air gets in the system, and that will cause the car to overheat, from the coolant loss, not from the heater core.

Many cars have a valve under the hood and when the heater is not on, the valve closes, blocking coolant, but they do not overheat.

Keep in mine that a waterpump being a vane pump cannot push air, so if the coolant level gets low enough, it won't be able to pump the water it does have.

jaymac · Mar 20, 2006

well, blend door works, i checked that out.
I know coolant level gets low from the broken bolt leak.
And heater core's never been replaced (88), so it's prob. clogged up anyway...

Daggar · Mar 20, 2006

90mustangGT said:
A certian amount of coolant goes through the heater core, but then runs to the t-stat area. If the heater core was clogged, the water would just flow past it, it would not effect cooling efficiency.

Ahh good. Someone "IS" thinking.

I saw that someone else was asking whether the heater core could or should affect cooling. Sure it can, but not in the manner that has been suggested in this thread. 90mustangGT is right on!

Daggar · Mar 20, 2006

jaymac said:
Well, water pump is new. Rad was replaced as well, but you're right, it's the 4 cyl. unit.
Deflector is still there.
I do have a coolant leak from a broken water pump bolt, so there are air pockets from time to time.

... and this is why I generally stay away from threads started by Jaymac. Dude... why are you finally getting around to this information 12 posts (5 of them yours) into the thread??? Didn't you think that this information would be important to a question about a heating/cooling problem?

Troubleshooting 101:

Look at and evaluate ALL available information. Don't just pick and choose because you think you might have a theory or you would prefer one malfunction over the other. When you're asking a question about a problem, list ALL of the related factors. Not just the ones you think fit what you would like for the issue to be. If you "want" it to be the heater core then there's no reason to even post the thread. lol

jaymac · Mar 20, 2006

Daggar said:
... and this is why I generally stay away from threads started by Jaymac.

Wow. That's devestating. Truly, truly harsh.
I don't know what to say...
Sorry I wasted your time w/ my incomplete inquiries....
Next time just pass me by and let someone else waste their time; I won't mind.

jaymac · Mar 21, 2006

And Daggar (if indeed you haven't started bypassing my posts already), if you'll notice in my first post, although I gave a brief history, my ONLY question was if "you think bypassing it might lower temps."
I wasn't asking for diagnosis help, as I know what other issues exist, and therefore didn't feel the need to mention them again.
All I wanted to know was if by-passing the core would help, if indeed it was clogged.
That's it.
I appreciate everyone who did help me try to diagnose it with good intentions, however.
Thanks to all who chimed in!!
J

Can I bypass the heater core to lower H20 temps??

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