question about coolant line under throttle body

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TrendsetterAuto
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Joined: Sun Jun 19, 2011 9:35 am
Car: 1990 infiniti Q-45
Location: Kelowna B.C. Canada

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Hey guys, I'm deep into my 1990 Q45 doing all the under plenum service, knock sensors, valve cover gaskets,and possibly injectors. My question for you today is while I was cleaning out the plenum & Egr, I found the coolant lines that run under it and in throttle body were plugged right up. I've cleaned it out from both ends but I cant get any flow through the part below the actual intake tube, there is a valve there that is spring loaded and tied into the throttle cable action somehow, So i don't know if I should even be getting flow through there, but i manually opened that valve and still no flow. Any ideas? I'm gonna go check the fsm for diagrams now, i just really dont have a clear understanding of the function of this line so I'm a little nervous to open up something that wasn't needed.


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Infinitiguy19
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Joined: Sat Dec 22, 2007 4:58 pm
Car: 1993 Infiniti Q45 188580 Miles
1994 Infiniti Q45a 240000 Miles

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The T-body has a Thermostat (T-Stat) built into it. Like a choke its used when the engine is cold. It allows the engine to warm up.

I plan on rebuilding a T-body some day after I rebuild my diff, trans and power steering rack. So I will let you know how it works later on.

OwnerCS
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Pictures of the plenum underside are posted below. The first picture below shows the underside of the throttle body with the cooling line input and output fittings.

Image

and

Image

the plenum rebuilt (e.g. all hoses replaced) and installed as an assembly like the picture below.

Image

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Q451990
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I'm fairly sure coolant just flows through that area to help warm up the fast idle cam that Infinitiguy mentioned. I will try to remember to check one of my spares in a little while to see if it's free flowing...

Heath

TrendsetterAuto
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Joined: Sun Jun 19, 2011 9:35 am
Car: 1990 infiniti Q-45
Location: Kelowna B.C. Canada

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Thanks a lot, hope I can get a definitive answer here. In my mind i would think that one way or another i should be able to have flow through there and at this point even when I manually operate that valve (thermostat) I get no flow whatsoever even whith compressed air. Maybe I'll try dig a little deeper. Any ideas or tips on how to safely remove that little thermostat for better access

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Q451990
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Car: 1990 Q45 - 118K, 2022 Toyota 4 Runner, 2004 Frontier M/T - 108K, 2012 Xterra (Mom's), 2023 Rogue (Inlaws)
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I checked one of my spares, and I could blow freely through the coolant lines in either direction. Same for the vacuum lines...

The "thermostat" isn't actually a thermostat - it's the fast idle cam - and it's some sort of wax filled device that, when warm, softens and allows the idle cam to retract. I wouldn't try to remove or adjust anything on the throttle body - Just stick to cleaning it. Maybe try poking some kind of wire through those coolant tubes?

Heath

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Infinitiguy19
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Joined: Sat Dec 22, 2007 4:58 pm
Car: 1993 Infiniti Q45 188580 Miles
1994 Infiniti Q45a 240000 Miles

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Q451990
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Posts: 11473
Joined: Tue Jul 23, 2002 8:21 am
Car: 1990 Q45 - 118K, 2022 Toyota 4 Runner, 2004 Frontier M/T - 108K, 2012 Xterra (Mom's), 2023 Rogue (Inlaws)
Location: Columbia, SC
Contact:

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:rolleyes:

My point is that it's a thermostat, but not in the traditional sense... as in there's not a tiny removable thermostat that sits between the cooling inlet and outlet on the throttle body. While the fast idle cam may be removable, it's not available separately - and messing with any adjustment on the throttle body is a bad idea.

Heath

TrendsetterAuto
Posts: 11
Joined: Sun Jun 19, 2011 9:35 am
Car: 1990 infiniti Q-45
Location: Kelowna B.C. Canada

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Thanks again guys, i did some reading about the wax filled device and how to adjust it based on its stoke at different temperatures and really hoped to not have to go there. I am glad to hear that you can blow air through yours, it makes me feel a little better about stuffing something through there, the fsm didn't really tell me what what to expect in there. At this point I'm still going over broken wires and corroded plugs and all the hard crispy bits that need attention. I though I'd pull it apart on friday night and put it all back together saturday, Here it is wensday and I think I'm done making a list of things to fix or pull off and use from my other motor before putting it back together. this is my third time under the plenum on this car and every time I want to go back even less than the time before. The knock sensors where so bad they had no housing at all on one and half on the other and the plugs were cracked right off from the sensors. It was definately time to do the valve covers as well,three spark plug holes were nearly full of oil! No wonder it hasn't been running very well.
If you can think of anything else that I should be sure to check out before putting this all back together it would really be appreciated, I've spent about enough money on this car this month but I definately don't want to go back in there for having overlooked something stupid.
Prior to taking it apart I had a bit of a miss but mostly erratic idle, it would bounce around a lot between 1000-1200 rpm and sometimes drop to 500 or so, sometimes so low I thought it would stall and then my brake pedal gets hard makes for a scary drive in town. The only code I got was for knock sensors, from what I understand, if there was more that one code it would flash them both alternately right?


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