Lost Fast Idle Function When Cold/Thermostat Replacement Issues

[faststandard]

My son and I have been trying to figure out why his M1009 has lost it's ability to fast idle/advance the pump when cold. When we purchased the truck, the old thermal switch was stuck closed and the truck idled fast with advanced pump timing all the time. Fast forward, we replaced the thermal switch with a new BWD part and all was well for a number of weeks until one day it did not idle fast when cold. In addition, he noticed that thermostat housing was leaking.

Well, since we had to drain the coolant for the thermostat replacement, we decided to purchase another thermal switch (local parts store was kind enough to replace the old unit under warranty) and install it. The new one is installed and we checked for voltage at the wire when the key is turned on - everything seems to be correct in terms of function.

The issues that we ran into were on the thermostat housing - the lower bolt broke on us despite our best efforts. Luckily, it did not break flush with the cross-over tube so I welded a nut to the bolt and removed it that way.

What is everyone using for replacement thermostat housing bolts? The old bolt is a M10x1.5x35 with a flanged head grade 9.8. According to the TM parts manual, it indicates GM P/N 11513606 but that part number seems to pull up a non-flanged head bolt in the GM parts catalog. Am I missing something?

Thanks for the help as usual.

 

[cucvrus]

I would just use a flanged M10 bolt and some silver never seize. It is about as good as you can get. I had better success using an impact on them. That always worked for me. I tighten a tweak first and then hit it in reverse. The impact seems to be the trick. Good Luck.

 

[dougco1]

My son and I have been trying to figure out why his M1009 has lost it's ability to fast idle/advance the pump when cold. When we purchased the truck, the old thermal switch was stuck closed and the truck idled fast with advanced pump timing all the time. Fast forward, we replaced the thermal switch with a new BWD part and all was well for a number of weeks until one day it did not idle fast when cold. In addition, he noticed that thermostat housing was leaking.

Well, since we had to drain the coolant for the thermostat replacement, we decided to purchase another thermal switch (local parts store was kind enough to replace the old unit under warranty) and install it. The new one is installed and we checked for voltage at the wire when the key is turned on - everything seems to be correct in terms of function.

The issues that we ran into were on the thermostat housing - the lower bolt broke on us despite our best efforts. Luckily, it did not break flush with the cross-over tube so I welded a nut to the bolt and removed it that way.

What is everyone using for replacement thermostat housing bolts? The old bolt is a M10x1.5x35 with a flanged head grade 9.8. According to the TM parts manual, it indicates GM P/N 11513606 but that part number seems to pull up a non-flanged head bolt in the GM parts catalog. Am I missing something?

Thanks for the help as usual.

Your fast idle solenoid working?

 

[faststandard]

Yes, if you jump 12v from front battery the pump timing advances and the fast idle solenoid engages as it should.

 

[dougco1]

Yes, if you jump 12v from front battery the pump timing advances and the fast idle solenoid engages as it should.

Check that the switch wire from the switch to the injection pump is not compromised/broken. Not sure why a new switch would stop working to begin with. it should be normally "closed" when cold and continuously keeping power to the idle advance in till the engine warms up. once it warms up it "opens" the circuit and drops the power at the pump. Other than that, maybe a injection pump issue?

 

[faststandard]

Well, we got the truck back together this morning only to find that the t/stat hsg is dripping like crazy. Not sure why as we used a new Fel-Pro gasket along with anaerobic sealant. I will say that it appeared as though the original housing flange did not appear to be flat as it rocked while on a steel plate - like it was over tightened in the past. Also, the flange on the water cross over does not look to be the greatest either - it looks as though it may have been removed and dropped as the bottom flange area around the bolt is damaged. The leak is coming from this area. Will be looking to source some new parts. Anyone have a nos t/stat housing and cross over tube?

 

[faststandard]

Well, we got the truck back together this morning only to find that the t/stat hsg is dripping like crazy. Not sure why as we used a new Fel-Pro gasket along with anaerobic sealant. I will say that it appeared as though the original housing flange did not appear to be flat as it rocked while on a steel plate - like it was over tightened in the past. Also, the flange on the water cross over does not look to be the greatest either - it looks as though it may have been removed and dropped as the bottom flange area around the bolt is damaged. The leak is coming from this area. Will be looking to source some new parts. Anyone have a nos t/stat housing and cross over tube?

Or should I try a double gasket?

 

[frank8003]

You could fix it check it flat both sides with a proper stone. Normal stuff.
A lot of stuff gets worse when over-torqued down, sealed with funny stuff, and or generally not as per design of being FLAT.
I used to give these away but found 99% of recipients sharpened their silly little knifes whit them so I stopped making free.

 

[cucvrus]

Make sure the thermostat is properly seated in the flange groove of the manifold. I seen them slip and get tightened with the flange not seating. I would removed the entire coolant manifold and replace the small coolant gaskets on the heads and clean and file the thermostats housing as recommended. Good Luck.

 

[sneekyeye]

Do what I did and just use gasket maker on it. I could never get my thermostat gasket to seal with the paper gasket. Just a little bit on the housing flange with no gasket and it cured my seepage.

 

[faststandard]

Well the saga continues - the leak is still present. We took the thermostat and water crossover off the motor and cleaned/straightened all of the flanges (the ones to the cylinder heads just needed the gasket removed. Put everything together with a light coating of RTV on the paper gaskets and waited the full 24hrs to let the RTV cure. Just went out and filled it up with antifreeze and started the truck - after it ran/warmed up for a few minutes we noticed the slow drip coming from the bottom bolt of the thermostat housing.

Like I noted before, there is some damage to the lower corner of the cross-over that would require it to be machined in order to remove it fully.....and then you would have to re-machine the pocket for the thermostat itself or weld up the surface and machine it flat. It may also be cracked from when the bolt snapped off but it is hard to tell with it being aluminum casting. With that being said, does anyone have a new or good condition water cross over that they would be willing to part ways with?

 

[Tinstar]

Post you’re needs in the Parts Wanted Section of the Classifieds.

 

[faststandard]

Thanks for the tip. I was able to source a like new crossover on FB from out west - it should arrive today. Yesterday, we took the alternators off and had them tested at the local alternator shop - brushes/diodes/rectifiers all looked good inside and tested fine. We will be removing the old water crossover today. Also, we figured out the temperature switch - bad part received from parts store. We pulled an original out of a salvage yard 6.2l and it shows continuity across the terminals when cold. Our replacement BWD part does not. More to come.

 

[chevymike]

Thanks for the tip. I was able to source a like new crossover on FB from out west - it should arrive today. Yesterday, we took the alternators off and had them tested at the local alternator shop - brushes/diodes/rectifiers all looked good inside and tested fine. We will be removing the old water crossover today. Also, we figured out the temperature switch - bad part received from parts store. We pulled an original out of a salvage yard 6.2l and it shows continuity across the terminals when cold. Our replacement BWD part does not. More to come.

Is that the one from me?

 

[faststandard]

Is that the one from me?

Yes sir. It arrived just a few minutes ago.

 

[chevymike]

Yes sir. It arrived just a few minutes ago.

Cool, they were saying Monday. I hope it got there okay.

 

[faststandard]

Everything looks good. I wish it was a bit warmer so we can work on it. We have to remove the old crossover and get everything cleaned up and the fitting removed in order to install on yours. I can't believe that it arrived so quick from CA.

 

[faststandard]

Good news to report. We disassembled the truck and cleaned all of the flanges a 2nd time. Thanks to ChevyMike we got another water crossover and t/stat housing. We bead blasted those and got them all cleaned up prior to installing our heater hose fittings. Got everything buttoned up last night and let it sit overnight. My son and I just refilled the coolant and started it up. We had our fingers crossed while it was warming up and we are happy to report that everything is leak free. The truck is cooling right now and we are going to drain the coolant again in order to install our new temperature switch for the cold/fast idle system. This switch is OEM and bench tests properly - switch is closed at temperatures below a 100 deg F or so. Will report back shortly.

 

[chevymike]

Awesome! Glad the new crossover worked for ya.

 

[faststandard]

More good news to report. We took out the BWD thermal switch and installed the OEM unit pulled from the local salvage yard. After getting the harness back on and the coolant refilled, we let it sit until last evening (~25 deg F outside). We then went out and started the truck and am happy to report that we now have our cold advance/fast idle function back. Not sure what is going on with the BWD thermal switches but at this point I cannot recommend them. the first unit lasted about a month or so and the 2nd unit was DOA out of the box. Luckily the local parts store agreed to give us a refund on both units.