heater core bypass?
 

has anyone ever done a heater core bypass??? did you see better mpg from it?
i think it would help without

If you have a really short commute it may be worth while to look into. Other than that I don't see it having much effect.

oh well your probably right :(

Any idea how much coolant the heater core holds? I think my entire coolant system for my ~1.5L engines hold about 1 gallon. If we get a few numbers on things we can calculate what % of thermal mass the coolant in the core consists of versus the coolant in the engine and the thermal mass of the engine.

6 liters well im thinking about how the coolant is circulating all the time

Yeah I understand. By bypassing the heater core you would lessen the initial amount of thermal mass you need to heat to get the engine up to temperature which means you get up to temperature faster. Its not a bad idea, we just have to determine if we're actually reducing that by any notable amount. My initial guess is probably not, but it can be calculated.

My heater core has a valve on it that it only opened up when the heat is turned on.

My cars do also.

I've read on performance sites that a heater bypass can cause hot spots in the engine due to changed coolant flow.
It's better to simply block the coolant lines to the heater if you want to remove it.

ya your right on :) wait how can we calculate it?

cool! what kind of car you got? can i buy the value aftermarket? for say a 97 nissan pickup lol

I'm not sure if my heater hose mod is what you have in mind, but here goes. I bought a Four Seasons valve from Autozone a couple years ago and spliced it into my heater hoses. With it I can let coolant circulate as normal, or I can return coolant directly back to the system and bypass the heater. It's actually a factory Jeep part, vacuum actuated. I did it to improve my air conditioner performance, not to speed warm ups.

thats sweet man that sounds great thanks

Four Seasons 74809. Here's a thread at DodgeTalk from my install notes... DodgeTalk : Dodge Car Forums, Dodge Truck Forums and Ram Forums

Sounds similar to what I did with my truck. I used a Four Seasons 74777, though.

All of the heater valves I've come across will allow some seepage past the valve itself. I suspect this is intentional, so as force all of the coolant to stay at a uniform mixture. For bypassing the heater core, the seepage isn't enough to really affect discharge air temperatures coming out of the HVAC housing.

However, for fully shutting off coolant flow, such as with my HAI setup, these valves are not quite adequate.

how much quicker sis your truck warm up?:thumbup:

What ever you do, do not block or disable any coolat bypasses.
If you want to bypass the heater core, go for it, wont hurt anything.

Oh why can't I? I did bypass the TB one time and it didn't hurt anything but I didn't see a inprovement so ya. But will it hurt anything if I bypass the heater core????

You may bypass the heater core, TB or anything.

The idea is to keep coolant circulating.

The vehicles that have the heater core valve, most of the time its a 3 way valve so even if coolant isnt going through the heater core its still circulating.

oh okay :) and when i do the bypass it will be a 3way valve thanks for the input ::cool:

It's hard to say how much warmer my truck would warm up with the bypass, as I've never really tested it. I installed my heater core bypass to make my A/C put out colder air.

For some engines, one can get away with using a two-way valve. However, that presumes a good understanding of one's engine internals. For instance, on my truck's engine, there's already an internal bypass between the heater supply port and the heater return port.

Would it not be the same as leaving the temp dial set to cold? Like we've always done it? Or are we talking about removing the heater core completely? Because thats a bit excessive, given that most of us need it!

older vehicles with A/C had a factory heater bypass valve installed. Newer vehicles do not. All well and good, except for the fact that there's still heat going into the cabin of the newer vehicle.

All we're talking about is installing a valve to bypass the coolant flow through the heater core during summer months, and during warmup.

Generally, one could get about a 10 to 15 degree colder discharge temperature coming out of the A/C, with a heater bypass in place. As for warmups? I'm not entirely sure a heater bypass would provide any sort of measurable decrease in warm-up time.

is there any way i can mess up my motor by doing the bypass? i have a 97 nissan d21 pickup aka nissan hardbody 2.4L

Well, if you install a bypass and don't properly remove all of the air out of your cooling system afterward, then it is possible to do some major engine damage. Not terribly likely, but it is possible.

However, if the bypass is properly installed, and the coolant system is properly burped of air, then the bypass itself should not cause any problems.

okay sweet no prob can do :) thanks for the q and a :)

When I installed my heater core bypass, I used some C-clamps to clamp the hoses closed, then cut them so I could minimize coolant loss while trying to shove the valve into place.

Question: If you bypass the heatercore, warm up, then turn on the heat, would the cold coolant entering back into the engine cause any potential harm? I know it's not a lot of fluid and it will probably warm up quickly, but isn't metal not a big fan of a quick cool down, even in small doses like that? I don't think it would crack a block or warp a head by any means, but is it possible that, with enough uses, it could cause some potential long-term damage?

No. The temperature difference isn't that large. Its not like your engine block is glowing cherry red and you're dropping it into a huge vat of water. That would be a problem. :) Your engine gets sprayed by water all the time when you go through puddles, this is no different.

On a Jeep 4 cylinder if you bypass the heater core or block the heater hoses of the engine over-heats. Its in parallel with the radiator, but does not get controlled by the thermostat. I finally stuck a valve in the hose to meter the flow until I got the new heater core in.

Later model jeeps (89 and up) dont use the old valves, they use a damper that blocks the heater core out of the air flow through the duct exactly like a chevy pickup.

I use a cheap harbor freight IR gun to check temps.

Dave