DIY: TB Coolant Delete
 

So I finally went and did it. You can read the pre-discussion about this idea that took place a while back here: http://www.the370z.com/vq37vhr/3041-...le-bodies.html

These are two pics I posted in that thread, which are marked up images from the Service Manual, showing the hoses we're talking about and the engine coolant flow diagram:

http://www.the370z.com/members/wstar...nt-svc-man.jpg
http://www.the370z.com/members/wstar...-svc-man-2.jpg

The bottom line is, afaik, deleting the TB coolant lines *might* shave some heat off of your intake air (but you won't see it on OBD-II data since this occurs after the sensor), and get some hot coolant lines out of the engine bay. If you live in a cold climate, you might not want to do this, as the purpose of the OEM TB coolant lines is to prevent your throttle plate from icing up and getting stuck in place. Basically, they circulate hot coolant through a channel that wraps around each TB.

In all likelihood, this mod won't do much for you. But on the other hand, it's cheap and easy, so why not :)

Anyways, on to the DIY job.

First, these are the parts, which cost less than $10 at your favorite random auto parts store. You need hose clamps (smallest ones you can find), and "bypass caps" (like vacuum caps, but hopefully more resistant to pressurized hot coolant). I'll go into more detail later about sizes and issues with these:

http://www.the370z.com/members/wstar...2192-parts.jpg

Here's what everything looks like at the start of the job (note, I've already removed the strut tower brace and the upper intake tubes of my Stillen intake. Remove those (or OEM equivalent) before starting):

Engine Bay:
http://www.the370z.com/members/wstar...-bay-start.jpg

Left (driver) TB:
http://www.the370z.com/members/wstar...left-start.jpg

Right (passenger) TB:
http://www.the370z.com/members/wstar...ight-start.jpg


Before going any further, make sure that your car has cooled off enough to relieve pressure in the cooling system, and remove the radiator cap!

I started on the driver's side. First, place some paper towels underneath the TB connections, to catch the coolant that will dribble out:
http://www.the370z.com/members/wstar...left-towel.jpg

Now, disconnect both lines at the TB. There will be some minimal dribble (only one is disconnected in the pic, also remove the one next to it):
http://www.the370z.com/members/wstar...-left-disc.jpg

Next, you need to remove the other ends of those two lines. One runs straight into a hard line that runs along the rear of the engine, and is not tricky:
http://www.the370z.com/members/wstar...disc-upper.jpg

The other runs straight down and T's into a hard line along the driver's side of the engine. When you pull the other end of the hose off at this T, coolant will begin spurting out of the T in a sort of pulsing, arterial bleeding sort of way. You want to have a cap ready to shove on there immediately, and then try to wipe up the mess you made. This pic shows the cap already in place, since I couldn't really take a pic during the spurting :):
http://www.the370z.com/members/wstar...-cap-final.jpg

This is what the left side looks like when complete:
http://www.the370z.com/members/wstar...t-complete.jpg

Now on to the right (passenger) side. Again, prep with towels and start with removing the two lines on the TB itself:
http://www.the370z.com/members/wstar...ight-towel.jpg

Most of the rest of the right side will be obvious and easy if you made it through the left side. There's one hard part, but there was no way for me to get clear pics because it's back behind the engine :)

One of the lines from the right TB goes to the other end of that hard line along the back (you removed a line from the left TB to the other end of this tube earlier). The other line dives down behind the center of the engine block. Good luck wedging needle nose pliers and your hand down there to remove the factory spring clamp. What I ended up doing was basically pulling on the hose from above until I yanked it off, clamp and all. It's easier that way.

This connection will also spurt coolant like the T-connection on the driver's side did. Have a cap ready, and get it capped quick. Then have fun tightening a hose clamp onto the cap back there, and you're basically done with all the hard work.

Here's the right side, complete (although you can't see the pita part in the back of the engine of course):

http://www.the370z.com/members/wstar...t-complete.jpg

Next, you probably want to blow any remaining traces of coolant out of the throttle bodies themselves as well as the hard line along the back that you removed hoses from. I used a little air nozzle on my air compressor. You don't need a big compressor for this, even a tire inflater would be fine. Having a real compressor and one of these handy nozzles with the conical rubber tips is nice though:

http://www.the370z.com/members/wstar...2-air-tool.jpg

These are all the hoses/clamps you should have left on the garage floor now that they have been deleted from the engine bay:
http://www.the370z.com/members/wstar...hoses-gone.jpg

At this point, I washed out the engine bay a bit by running some water (garden hose) and kinda spraying it down into the engine bay in all the same places that I know I leaked coolant. Should help flush the nasty sticky coolant off and make it not smell so bad when you next start things up. Be sure not to spray water into the throttle body intakes, of course.

Make sure you remember to put your radiator cap back on tight at the end as well, and then reinstall everything else you took off (air intakes, strut tower brace, etc).

Some notes about the caps and clamps for the bleeding hard lines:

In the package of assorted bypass caps I picked up, the smallest sizes were 3/8" ID and 1/2" ID. The 3/8" ID one fit the connections fairly well (although it could have been slightly tighter), but even the smallest hose clamps I could find wouldn't clamp properly onto these. I ended up putting the 1/2" ID caps on top of the 3/8" ones, which added enough outer diameter to make the hose clamps work properly. This setup makes me a little nervous, so I'll be watching these two spots (as well as my coolant and oil temps) like a hawk for the next few days to make sure it works out ok. Probably an even more secure (but uglier) solution would be to cut small lengths of the original hoses, clamp them on with the original clamps, and clamp a bolt into the other ends of these sections to cap off the line.

I let the car warm up in the driveway after install until the oil got up over 160 (coolant had been stable at it's usual driving number of LEDs for quite some time by then), constantly rechecking the caps with a flashlight for any sign of leak. Then I went for a short test drive and came back, and all seems well. I'll update here if there are any issues over the weekend.

Obviously, you're on your own with this if anything goes wrong. Don't do it unless you at least kinda know what you're doing. If at the moment you remove the first coolant line, your engine explodes and kills your dog and sets your house on fire, I accept no responsibility for your stupid actions.

Very cool DIY, wstar, thank you. I agree with your rationale, if you live in warmer climates, this mod might help intake air temp.

The only thing I'd personally done differently (I tend to make life harder for myself for some reason, probably a split personality disorder where one does not like the other) is cap the coolant intake and exhaust tubes on the throttle body itself, to make sure no wasps decide to burrow in there, or that anything else makes its way in there for whatever reason, in case I'd like to re-install this TB coolant system in the future.

Keep them coming!!!

Yeah it's not a bad idea to cap those off, I just didn't bother, at least for now.

Is it possible for you to just tie the lines coming from the "in" and "out" of the throttle body together with a barbed hose coupler? I know it won't be as clean, but it will be much easier to put back to stock if anything happened. That would work right?

Also can you feel the engine to be more responsive? You know like when you first start your engine and drive off before everything heats up.

Thanks in advanced.

Abner

That would work fine....

I believe the Intake Air Temp is sampled at the MAF, upstream a bit from the actual TB, but regardless, cooler here is a good idea except maybe in really cold climates..

Cool thanks! I'll hit up auto zone here soon then!

Yes, bypassing the pairs of lines at each throttle body would get the coolant out of the TB at least. I figure if you're gonna do it, may as well go all the way and get those extra hoses out of the engine bay completely.

And no, I didn't feel any difference driving, and neither will you. It's a very tiny mod performance-wise, which might occasionally help your intake air temps by a very a small amount.

Interesting. Thanks for the writeup!

I understand about getting the rest of the hoses out of the way, I just wanted to keep the line there just in case I would have to bring the car in for anything. The part where it connects behind the motor sound like it would be a pain to try and get the hose back on LOL!

Actually, there's an even better option if you want to keep it simple:

Just disconnect one hose from each TB, the front-most one (leave the other one connected). These are the ones whose other ends connect to points 'C' and 'E' labeled red in the diagrams at the top. Plug the two disconnected rubber hose ends (like, find an appropriately-sized bolt, stick it in the line, and then use a small hose clamp to secure it, such as the ones already there on the line), and then blow the leftover coolant out of the now-disconnected part of the system (blow air into the open metal connection on one TB, and the water will shoot out the open metal connector on the other).

I am not sure if there would be any advantage but it would be interesting to run C02 through the newly opened connections on the throttle bodies to actually cool them as the gases pass through. Similar to the Cry02 system did with the cooled throttle body spacer kit. The C02 could be vented to the atmosphere or directed to vent over an oil cooler perhaps.

Nick

Sounds like too much expense/complication for very little gain, but who knows. A throttle body probably doesn't make a very good intercooler, which is what you're basically trying to simulate. Also, if you actually achieved significant cooling at the throttle body, you'd be artificially leaning out the mix (denser intake air) post-MAS-sensor, so the car wouldn't adjust for it and might be more likely to knock if you went too far without adjusting the sensors and/or ECU for it. I have no idea what numbers it would take to do that temperature-drop wise.

It wouldn't actually lean out the mix since the MAF reads all the air that goes through. Take it to the extreme to show the principle.

Imagine you make the air at the throttle a lot cooler. The contraction of air would create a vacuum and pull more warm air through the filter, past the MAF. Making it cooler allows more air to fit in the same space, it doesn't add oxygen to the charge, which is what would cause it to run lean.

Before someone thinks this is an opportunity to hi-jack this great DIY thread, this is one of those things that would really need to be a HUGE change and I agree with wstar, this is a great mod that simplifies the cooling system, doesn't heat the TBs and even saves a pound or two in hoses, clamps and the fluid inside. It's likely not going to add a difference that would be greater than the margin of error of the method that you use to measure. No one would likely disagree that this modification is a good move for those that don't worry about the TBs freezing shut (is that really a problem?).

OH AND BY THE WAY:
Where is the shot of the engine bay all put back together?

in.the.dark, I think wstar is right. The MAS does measure how much air goes by, but it also measures in how big an interval of time, and at what temp it was, and adjusts the fuel-air mixture based on that. By cooling the air at the throttle body you increase the density, and that new density is what arrives in the cylinder and is burnt. No one added oxygen into the air, but now there is more oxygen in the same stroke volume, and the mixture is lean.

I donno, in.the.dark may actually be correct on this. I guess it depends on exactly how the mix is calculated by the ECU? I don't know enough to say for sure. But he's right that if you appreciably cooled the air post-MAS, the MAS would see a higher flow volume of the hotter air. Whether that makes everything equivalent in terms of what the MAS measures and the ECU calculates is what I'm unsure of.

I don't think the cooling of air at the throttle body would increase the air flow in the intake. The air flow is dictated by the engine suction, which is based on volume, not density.

The same mass of air, when cooled, consumes less volume as the density increases. It's all related.

I did this same mod on my Z32, but I don't think I would do it on my Z34. I had the engine apart and wanted to minimize hosing and complications in the bay - the bay that has one of the worst reputations in the world. The engine (I mistyped coolant here) is approximately the same temperature as the coolant inside of it. Therefore, the metal TB is roughly the same temp by means of the aluminum heads or the coolant itself. Sure, I certainly think it will take longer for them to warm up without the routing, but running on a cold engine is frowned upon anyway.

- Clay

Edit: 090711 0725 GMT

Sounds about right. I still prefer having the hoses gone. Maybe someone will do some insulator type thing eventually for the intake manifold and throttle bodies, to keep them from sucking up so much direct heat from the engine metal.

Interesting concept. I am still undecided, but the work seems easy enough.

I do find the idea of adding a cold charge to the opening a nice one up on the mod. All though it depends on how exactly the ECM calculates injector pulse with. Most modern cars rely more heavily on the up stream 02 sensor to calculate and adjust the a/f ratio. I'm pretty sure even a real cold blast would not change to ratio beyond normal engine rich lean switching for catalyst efficiency. But could be good for a little extra pick me up. I think every 10 degrees is good for 1% HP increase.

Im not doing the delete but I am swapping all the hoses out to red silicone hoses and for the GOD DAM LIFE OF ME! I cant get the last hose that connects the the back of the engine!!!!!! GRRRrrrrr!

Doing this all now as imm typing this looking for any pointers! HELP

ˆ YEEESSSSSSS!!! After a whole day! I have done it!!!

I just put a bypass valve on the inlet hose to the TB. Hot weather, shut it down so antifreeze won't flow around TB. Cold weather, turn the lever and open up the flow. Did This on my Titan years ago.

thanks for the write up...

took mines off for cleaning and posed the question which this thread answer perfectly!

Im wondering if nissan designed that so that the engine coolant would have a sedond means of cooling. Have you noticed any increase in temp yet?

It wouldn't be significant enough for that to be a design consideration really. It's hardly even enough flow/surface to be significant in the other direction.

:iagree:

This was put on for places like Canada and Antarctica, lol
It keeps the throttle bodies from freezing, that's about it

what a amazing sharing,,,But too hard for me to do so

Bump! I just want to keep this thread in the up pages up front so i can find it soon. I will be doing this within the next days

Thanks bro for posting this DIY in 09, and thanks to the forum for keeping it alive.. Just did it... Much easier when you tell some one how to do it and watch :rofl2: ...

http://www.the370z.com/members-370z-...ml#post2280987



Thanks again WSTAR mad scientist :tiphat: ..

Only issue I have with this is capping the ports. The system I'd guess needs to flow in a circular direction. By not connecting C to E makes me uneasy. To do this very easy just take the passenger side front hose that connects to C in the back of the motor and flip it around to attach to E on the drivers side. Then remove all the other hoses. This way coolant still flows as designed and no more heat to the TB's. I've done this on every car I've owned. Before the TB is about 200 degrees hot like the coolant. After they are damn near ambient temp. Only way to test is drive down the road, quickly pull over and touch the TB's before and after. Touching them after sitting wont do anything since the TB's will heat up from engine bay heat soak.

FYI I lived in Ohio my hole life and never had a freezing issue.

Here's the hose from C that used to go to the front passenger side port. Flip it around and attach to E. pretty sure nissan did this on purpose cause the hose is a perfect fit with perfect bends!!

FYI guys who capped their system. In my experience the rubber/silicon caps from autozone or alike are extreme junk. Pull one off your car after being on there for so long and let me know how the dry rot looks. They crack and break extremely easy.

http://i39.photobucket.com/albums/e1...ps8b470afb.jpg

http://i39.photobucket.com/albums/e1...ps1e1838ce.jpg

So when switching to the M370 manifold you actually disconnect the TB coolant lines anyway, yes?

I just took the Allen bolts off and left the tb's connected....shortcut!

True that's a good call. I'm just surprised the install instructions don't even mention it and they call for disconnecting the TBs

FWIW, I do currently run a bypass hose like synolimit mentions. I used a length of blue silicon 5/16" hose (from Z1 I think). I did that because I never found a cap solution I was happy with (they would tend to leak over time; there's just no good way to secure a rubber cap against that kind of heat+pressure). But I really don't think there's a flow reason to do so. The tiny amount of flow that goes through the TB lines is insignificant in the big picture, and parallels two other much larger bypasses (the true bypass and the heater core bypass).

I am guessing the reason for the coolant through the throttle bodies is kinda like carb heat on a small piston aircraft. Prevents icing in the throttle and rough running or stalling. I would say do it, you're not in an airplane and I live in Texas so it won't get too cold here.

Quick question:

What size diameter would the metal bypass tube need to be to fit inside the throttle body coolant supply hose?

I believe the rubber tubes for the throttle bypass flow are 8mm (aka 5/16") inner diameter roughly.

Perfect and thank you. Going to make up a couple bypass tubes this evening.