LQ1 Thermostat R&R: How ?

[Padgett]

OK I get it. Mechanics don't like the LQ1 because even minor things require either major disassembly or hydraulic assist.

 

That said I need to replace the thermostat because either is none or it is stuck wide open and MPG is in the toilet.

 

OK I got the airbox out, have the nut on the coolant pipe holder off. Now what the %^%^&&$( do I need to remove to move the coolant pipe far enough to get the water neck off ?

 

 

FSM says to remove the fuel lines and sounds like the throttle body. Really ?

 

Don't want to cut off the flange but will if needful.

 

Help!

 

 

[Psych0matt]

I usually don't reuse that thin bracket, never had an issue

[Nas Escobar]

There's a small rubber hose that connects that line  to the throttle body. It may be worm clamped on or alligator clamped on depending if anyone has messed with it. Take it off and the line should move out the way.

 

Easiest way to take that t stat out is by taking off the plenum. Gives you more room to play with. You don't have to mess with the fuel lines at all.

[Psych0matt]

[Padgett]

1) that is part of the reason I live in Orlando.

 

2) The bracket is welded to the coolant pipe.

[Psych0matt]

Because surface rust scares you? Wimp. But yes it is, I bent it out of the way

[Padgett]

OK bent and removed. Did need to make a "thin head" 13 mm wrench.

 

Does it need that brace ?

 

Final question: the o-ring on the thermostat is the seal, there is no gasket ?

 

ps rust does not scare me, just have a life without it. Cracking the coolant pipe now...

 

pps Was a 195 thermostat but innards were cocked and was partly open

 

pps been wrenching since the early 60s. Made a lot of mistakes. Am not afraid to ask of those who have been in there before. Now a 3800 or electronics or Pontiacs with carbs (like trips or dual quads) or use of a UniSyn am happy to help but this LQ1 is (a) complex and ( unknown territory. Have the FSM and parts books but sometimes "here a miracle happens".

Edited April 17, 2016 by Padgett

[55trucker]

 

[55trucker]

OK bent and removed. Did need to make a "thin head" 13 mm wrench.

 

Does it need that brace ?

 

Final question: the o-ring on the thermostat is the seal, there is no gasket ?

 

 

Be careful when you start distorting tig welded tabs on old coolant tubing, if you crack that tube you've then created another problem for yourself.

 

Yes that brace is necessary, it's supports the coolant bypass tube.

 

No gasket.

[Padgett]

Bent out of way like Psych0 suggested. Cracking tube was my concern also. Think I'll leave bent, tube is not going anywhere & don't want to tempt further. Will make test run to temp before putting the air box back on.

 

Using a 180F thermostat computer should be all in by 160F. Is a Delco thermostat so do not expect to open as fast as a Superstat (Stant does not make a 180), expect full open at 190F and should stay under 200F.

[Psych0matt]

I didn't say anything about it being the proper way, but it's worked for me on three different cars. As far as I could tell it was just kind of extra support that wasn't needed. As long as everything is bolted down tight I don't see it being a major issue.

[Padgett]

Well bracket is now tight against the exhaust shield. Filled it up & bled. Ran up at idle. Hit 183 and then dropped to 179 so working properly. Let it go up to 220 and checked for leaks. Nada. Looking good. No sweet smells. Leaving to soak for a while with clean drip pan under. When cooled off will make final check, top up coolant if needed, then button up.

 

BTW what size is that bleed screw. Bottom is 10mm but top: Not 7mm, not 8mm, not 1/4, not 9/32, not 5/16. Don't have 7.5 mm or 17/64. Finally used small needle-nosed vice grip. Don't like not having the proper tool.

[digitaloutsider]

I'm 99% sure I've always used 7mm on the 1G bleeders.

 

Also, I bent all my LQ1 brackets the same way Matt did.

[Padgett]

Well add me to the bent bracket group. My other GM cars are much easier to service.

 

Need to clean the IAC now, have had to do on nearly every 20ish year old GM computer car I've had. (code 35, high idle when cold). Even wrote up the procedure.

 

Remember to put a cloth under the IAC before removing screws. They are small and non-magnetic.

 

Update: was very dirty and idle seems a lot better now. Screws were magnetic and Torx-T20. Do these have quite a DFCO map ? Takes about 7 seconds to come back to idle when revved.

Edited April 18, 2016 by Padgett

[RobertISaar]

Update: was very dirty and idle seems a lot better now. Screws were magnetic and Torx-T20. Do these have quite a DFCO map ? Takes about 7 seconds to come back to idle when revved.

 

that isn't DFCO so much as the throttle follower. GM did weird things with the calibrations on the manual cars to where quirks like that happen.

[55trucker]

Do these have quite a DFCO map ? Takes about 7 seconds to come back to idle when revved.

Unlike the auto trans where the converter *slips* to prevent shock thru the driveline when throttle overrun is applied the manual trans units apply the overrun more gracefully.

[Padgett]

Well on a cold start the idle is staying up over 2k for too long (several minutes) & setting a code 35. Eventually it throttles back to normal (under 1K) but it take several blocks on a 80F day.

 

Is this normal ?

[vipmiller803]

Well on a cold start the idle is staying up over 2k for too long (several minutes) & setting a code 35. Eventually it throttles back to normal (under 1K) but it take several blocks on a 80F day.

 

Is this normal ?

No

[55trucker]

 

 

Is this normal ?

Code 35 - Idle speed control

 

That would suggest to me that you've a vacuum leak somewhere, when the system is open loop it's not possible for the default fuel program to overcome it, but when the engine warms up & the system goes closed loop the problem isn't dramatic enough to prevent the ECM from closing off the IAC to get around it.

 

Pull off the intake snorkel and visually look to see that the throttle blade is completely closed in the bore.

Have a look at your PCV valve rubber hoses, they do get brittle & crack.

[Padgett]

Thank you, minor vacuum leak makes sense. I'll check it out.

[Nas Escobar]

Well on a cold start the idle is staying up over 2k for too long (several minutes) & setting a code 35. Eventually it throttles back to normal (under 1K) but it take several blocks on a 80F day.

 

Is this normal ?

 

Yeah, code 35 is an idle issue. Your IAC can't control the idle. I have the same issue on my 93 Lumina Z34, however with me it's reverse. It will start normal but suddenly accelerate itself. Bought the car like that, have made the acceleration less frequent but it's not normal at all.