The search lacks... Coolant bypass, throttle body cooling, what gives?

[tmoore4512]

Okay friends, let me pose a question to you:

 

Why, on these WD21's do we have cooling circulating through the intake and throttle body? Is this a requirement or can it be omitted? 

 

I ask because the little bypass hose on the firewall side continues to die, so either I put PTFE in place with some sort of heavy duty crimps or I keep replacing this little monstrosity that is in the absolute wrong spot for someone with massive hands.

 

Before you search guys get mad, obviously I searched, but I kid you not, when I was first a part of this group/forum the search worked much better. Not so much today.

 

Anyway...

 

Any of you experts have any insight? On a VG30E, what is the meaning of this? Looking at the service manual is baffling.

 

I am about to just delete it.

 

Open to your thoughts!

[level9]

The coolant runs through the rear of the intake in order to let the idle air control valve know when the car is at operating temperature so it can disable cold start/fast idle. Note this car has two IACVs. There is the normal one on the bottom of the intake (ECU controlled) and then the one the coolant runs through at the top (mechanical only) which is only for cold start/fast idle. In theory, you could disable/bypass this but you may be stuck in permanent fast-idle mode (~1200 rpm). EDIT - I think the unit may also have a backup/internal heating element (hence the connector), so maybe not permanent fast idle if coolant lines disabled - but longer than normal.

 

The coolant lines then run through the throttle body. Best I've ever been able to determine the purpose of this - it's to prevent the throttle plate from sticking in cold climates because - in theory - it may be possible for some ice accumulation on the plate (safety issue). I had bypassed this when I lived in warm-climate TX but put it back when I moved to CO. I replaced all of those coolant lines with high temp reinforced silicone coolant hoses from HPS (and sealed with RTV at the barbs). Never had an issue since...

Edited August 17 by level9

[Slartibartfast]

Is the hose itself failing, or just leaking at the end? I ask because the steel lines the heater hoses hooked to on the VG33 I'm working on were rusted to absolute buggery at their ends. I don't know how they weren't leaking yet.

[tmoore4512]

Good info level9, was unaware even though I have been in and around the FSM for many years. Always down to learn!

 

What is HPS? I have been using fuel injection hose and it has been holding up about two years at a time.

 

Sorry, Slart, the hose itself, not the metal. Super frustrating.

[Slartibartfast]

I'll bet the fuel hose is the problem. There are different kinds of rubber used depending on what kind of fluid they're up against. I've heard of (and seen!) rubber meant for cooling systems swell and get squishy when exposed to oil. Looks like fuel line and coolant don't like each other, either.

 

Looks like HPS makes silicone hoses. If you can't get a standard hose at a decent price (or want fancy candy-colored ones), that could be a good way to go.

[level9]

20 hours ago, tmoore4512 said:

What is HPS? I have been using fuel injection hose and it has been holding up about two years at a time.

 

https://hpsperformanceproducts.com/

Not the cheapest thing, but I intended to never have to deal with it again 

Silicone is fine for vacuum lines and coolant lines (reinforced in the latter case for the pressures) but also worth noting can be more difficult to seal at the ends (hence I use coolant-exposure-rated RTV for added insurance).

It's true different kinds of rubber - of which at this point there's so many I've lost track - are good for different kinds of things and will fail if mis-applied.

Here's my cheat sheet:
For fuel hoses, I replaced everything with Gates Barricade except for the submerged hose in the tank/pump which was some super special snowflake stuff (fuel submersible rated) - and wildly expensive.
Crankcase ventilation/PCV - Gates PCV/EEC
Vacuum/Coolant - (reinforced) silicone as noted

 

[tmoore4512]

Well (expletive.) 

 

Thank you for the info. I have been turning wrenches for maaaany years and my brain did not put those two together. Totally makes sense.

 

Thank you for knocking the cobwebs off of this old head.

 

Checking out HPS now....

 

WOW. How have I not found this before. 

 

Thank you dudes!!! I owe you both a FEW beers....

[adamzan]

Some people do delete the coolant lines to the intake. Where you live it probably doesn't get that cold so it might not matter. My friend deleted them on his rig here in Canada and then wondered why it would run like @!*% when it was -20 and had low oil pressure on cold starts.

[tmoore4512]

Well, I guess that makes sense. I am neck deep in another timing belt/water pump job and I legit forgot why it was this way...hard to tell until it is all torn apart.

 

Now I am about to make another post. Front crank seal. 

 

Sigh.

[adamzan]

Good luck man, I have to do this job on my 1995, luckily I have the whole front clip off right now, easy access!