M35 Coolant Bypass Mod Install

[bigkevracer]

In the US, a popular mod on VQ35 powered cars has been the coolant bypass kit. Originally used on the VQ40 powered Nissan Pathfinders as part of their towing pack, the kit removes a blanking plate in the middle of the valley of the V6, allowing coolant to flow easier, and more coolant to pass through the radiator. This in turn lowers water temps.

Scotty nm35 developed a VQ25DET specific version of this bypass mod, to account for the turbo piping on the DET engine. At the same time he ditched the standard air bleed valve, a plastic pile of rubbish, and replaced it with a metal version with a tap for easy filling and bleeding of the cooling system.

So it was off to the super secret Pure Motorsport workshop for the install...

By day, a busy heavy vehicle and diesel repair business owned by my parents. Much like a good mullet, the front is for business:

But the back is for party. This is where I usually work on the car, lucky to have access to a hoist and tools. Sadly my usual spot was currently occupied by my little sister's Audi 80, which was having it's soon-to-blow engine replaced.

So a makeshift service location was setup behind the Safari-spec Jackaroo.

Looking down at the motor, the first step if you have to is to remove the cover of the engine, so you're left looking down at the plenum chamber:

First up, remove the hoses connected to the plenum and the four bolts and two nuts which hold the plenum down.

Next up, we'll need to remove everything fastened to the plenum. Start by removing the holts on the blow off valve return pipe, attached to the plenum:

Undo the bolt fastening what appears to be the bracket for the transmission dip stick.

Remove the three plugs to the right of the plenum chamber, and the two bolts which fasten it to the side of the plenum.

Undo the nut on the standard boost controller.

Undo the hose clamp on the throttle body, and unclip the wiring plug from the throttle body.

Remove the hose on the back of the plenum chamber.

Then simply lift the plenum straight up and off the studs. You'll be left with something like this:

It's a good idea to cover up the centre bores - you don't want to drop anything down into the engine.

Next up, we'll need to remove the fuel rail. There are two bolts on each side of the rail:

Once you've removed the four bolts, remove the plugs on the right hand side (air intake side) injectors. You'll then need to carefully lift the rail straight up to remove the injectors from the block. When you lift the rail, be very careful not to loose the o-rings and plastic retaining rings around the tips of the injectors.

Lift the fuel rail up and carefully pull it back onto the left hand side. I was able to hold mine in place by placing the blow off valve on top of it:

Remove the four plastic spacer rings that sat underneath the fuel rail mounting points and set them aside. Then you can undo the six bolts that hold that piece (injector manifold?) in place which will give you access to the valley:

Great success!

Now you can see the blanking plate we want to replace with the cooling mod, at the back of the block in the valley. Simply remove the four bolts fastening it down:

Then place silicone on the bottom of the new plate. The clear silicone can eat away at aluminium, so we used grey silicone. You can bolt the new plate straight down to the block.

You'll then need to put together the return hose. Insert the Proflow fittings into one end of the hose (you may have to heat up the hose), then fasten the supplied hose clamp onto the fitting.

Now this is where I made a mistake, and here's tip 1:

Tip 1: Don't trust Scotty's measuring.

Scotty was a bit too generous for his own good and supplied a bit of extra hose. All good, but it'll save a lot of headaches later if you take this opportunity to measure the hose from the block to where the tap will be (you will see the stock plastic bleed point in the heater hose behind the stock fuel pressure regulator). Trim the hose and drop the hose clamp over the hose, then insert the Proflow fitting (again, heat the hose) and tighten the clamp.

Connect the Proflow fitting to the plate on the block, and tighten it down. Make sure it's tight so you don't have to do the job twice!

I took this opportunity to give the injector manifold a clean in the kero bath, which isn't necessary to do:

You can then place the injector manifold back onto the block, and fasten it down. Dad caught me doing this and overtightening the bolts, which leads me to tip 2:

Tip 2: Don't over tension the bolts. Use a tension wrench to tension to 34NM.

I was quickly handed a tension wrench set to 34NM:

You can then insert the injector rail back into the manifold, and start tightening it down. That's when this happened:

Shit.

It looks like the bolt had cross threaded or binded and it just sheared.

A quick phone call to Andrew at AM Performance, and he told me he was at work, and able to have a look at it for me. I jumped into dad's parts hack and drove over there straight away.

Andrew set to work welding up the manifold and getting it ready to go. He was really happy to drop everything and help me out.

He was in the middle of helping a customer with a 4 door R32 replace the motor with a freshened up RB20.

Andrew was able to weld the manifold back together and get me back on track.

Andrew tells me that this is a common problem with Nissans, and gave me Tip #3:

Tip 3: When reassembling the engine, use high temperature thread lubricant.

I used a copper based Loctite product that dad keeps in the workshop.

I rushed back to the workshop and set to work putting the car back together.

After bolting the intake manifold down and tensioning to 34NM, I reinstalled the fuel rail and carefully torqued down the bolts to 34NM, or in the case of the repaired thread close to 34NM.

We then set about removing the hose clamps on the heater hose around the stock plastic bleed valve. The constant tension hose clamps were in the wrong location to be easily removed, and the stock plastic tap broke in the process. We also replaced the constant tension hose clamps with worm drive clamps just to make it easier to remove in the future. We fitted the tap between the heater hose and attached the Proflow fitting from the block to the bottom.

Thanks to the size of the new tap, we noticed the heater hose rubbing on the body and decided to cable tie it out of the way just in case.

You can then reinstall the plenum, working in reverse to the above removal steps.

Finally, bleed the cooling system. I chose to start the car, and carefully open the tap. There was a rush of never ending bubbles. I close the tap and waited until the thermostat opened, and reopened the tap, running it until the bubbles stopped. It only took a matter of seconds.

So I guess the next question is: Does it work?

I've seen two key benefits to this mod, which are exactly as suggested by Scotty:

• Bleeding the cooling system is now rediculously easy. Run the tap until no more bubbles. Doesn't get easier than that. I suspect this mod will really come into its own when you need to perform top ups of the cooling system, which I'll find out for myself in a couple of weeks when I replace the radiator and hoses.
  
• Coolant temps have dropped significantly. I noticed a 5 degree drop in coolant temps before and after. This may not seem like much, but ambiant temperature rose 10-15 degrees between before and after. I expect in like for like conditions you'd be about 15 degrees better off.
  

So remember the three tips so you don't bugger up the install as I did:

• Don't trust Scotty's measuring.
  
• Don't over tension the bolts. Use a tension wrench to tension to 34NM.
  
• When reassembling the engine, use high temperature thread lubricant.
  

http://performancewa...ass-mod-install

[PN-Mad]

Question is- can I be bothered going to the same extent with the VQ35de version of instructions.

[bigkevracer]

How different is it?

I would hope the only difference is pulling the plenum off, and there should be a tutorial online somewhere on how to do that.

I had an advantage doing this because I'd pulled the plenum off before to almost fit the plenum spacer, so I'd read the tutorial. Pretty straight forward.

Oddly I have two bolts left over...

[PN-Mad]

Different Plenum setup, fuel rail, and just some little things here and there. Once down to the lower intake runners its the same - but thats most of the battle.

I have to get it all off in the near future, so I might take pics.

[Daleo]

I have to get it all off in the near future, so I might take pics.

Please don't post them here Alex.

For the love of God please...

[Daleo]

Kick arse job on the "How To" Ryan; without the broken lug, you would've been home free.

[PN-Mad]

This is defiantly off topic... arrrrhhhh - be warned.

[iamhe77]

Nice writeup Ryan, so no coolant into the valley when replacing the plate?

Ours flooded immediately

• Don't trust Scotty's measuring.
  

*cough*

Edited November 11, 2012 by iamhe77

[bigkevracer]

Kick arse job on the "How To" Ryan; without the broken lug, you would've been home free.

Made good time until then Dale - probably take about 3 hours without the screwup I think.

Nice writeup Ryan, so no coolant into the valley when replacing the plate?

Ours flooded immediately

Nope. Took the plate off and the coolant was right at the brim but didn't flood.

This is defiantly off topic... arrrrhhhh - be warned.

Image link fail.

[Commsman]

Nice work Ryan . One of the best DIY's I've read - informative & entertaining all rolled into one. Even the pictures were in focus. What more could anyone want (other than you doing the work for us )?

Another thing to add to the long todo list..

[bigkevracer]

Nice work Ryan . One of the best DIY's I've read - informative & entertaining all rolled into one. Even the pictures were in focus. What more could anyone want (other than you doing the work for us )?

Another thing to add to the long todo list..

Tell you what Leon. You do the road trip down and I'll do it for you. Least I can do.

[scotty nm35]

So did you happen to measure the hose Ryan so I don't make the same mistake again? I cut at 380mm, I would rather not waste the hose as it's bloody expensive. (rated to 250 degrees I think, not 100 like most rubber hose.) Good job on the tutorial, I find it difficult to take photo's during installs, the missus won't let me use the camera with grubby hands.

I warned you the stock plastic bleeder is crap, lol, same thing happened to me trying to remove one, like it's made of cardboard. Can't say I have had an issue with the lug snapping off, but good call on the copper lube. I use it all the time on stainless and alloy threads to stop galling.

For anyone else interested, I will have a batch of laser cut 6mm alloy block plates this week hopefully. PM me if interested.

[bigkevracer]

Scotty, I think I cut 50mm out of the hose, but if the smell of coolant doesn't go away I'll be pulling it apart when I get back from Melbourne in case the hose on top of the valley is leaking.

I just used the phone, seems to have worked out ok. Wasn't game to use the good camera!

[scotty nm35]

The hose and push on fittings don't actually need the clamps but I put them in just incase, they will be fine as they seal tight, as you found out. The AN fittings you need to do fairly tight, perhaps with some antiseize also? The silicone on the gasket will stop any valley leaks. I am confident the setup will stand up to long term abuse without issues.

If one of the other guys can take a measurement of the hose length when they instal it I would appreciate it. I actually had the valley fitting facing the bleeder so it didn't foul on the rear cooling pipe, so I can possibly save 60-70mm more hose than what I supplied you Ryan. How hard was it to do up the block AN fitting anyway? Best would be doing it up in a vice first when you know where it needs to face.

Thanks again for the detailed guide.

[bigkevracer]

Yep, we had to get a mini blowtorch onto it to heat the hose up to get it onto the fitting (which was in a vice).

Question on the valley leaks: if there's a leak in the valley will the coolant drip down onto the ground eventually?

I can smell coolant in the engine bay, and I'm not sure if it's some remnants out of the tap or if it's a sign of a more serious leak in the valley. Besides topping the radiator up and watching the level is there a way I can check for a leak in the valley without stripping it down again?

[scotty nm35]

The coolant overflow bottle would be empty pretty quick if there was a leak and pressure wouldn't build in the hose. I would say more likely you dropped coolant onto the exhaust manifold and it's slowly burning off the heat shields.

A bit of wd40 should help the hose slide on. Perhaps a cup of boiling water to soften the hose would be better than attacking it with a blowtorch? lol. If I had the correct length hose I could pre-fit the ends...

[bigkevracer]

Don't you have a spare block you can measure up on? I could potentially measure up, but I cut about 50mm off and there was still slack in the hose.

[scotty nm35]

Nope, it has to be done in the car to get it exactly right, and I cbf taking the plenum off the wreck. If I do an instal here soon I will take note of it.

[180Shauny]

For anyone else interested, I will have a batch of laser cut 6mm alloy block plates this week hopefully. PM me if interested.

Only if your laser cutter gets off his arse and does something about it.

[scotty nm35]

Only if your laser cutter gets off his arse and does something about it.

Oi, back to work cutting my plates.