thermostat replacement

[IndianaVX]

Well, I'm thinking that my thermostat took a dump. And of course, the night before a long drive for a job.
After looking tha site over, I'm finding little on the subject. So I've got some. Uestions.
1) Is it the whole intake, or just the common chamber that needs removed?
2) If either the intake, or common chamber are removed, do I need new gaskets?
3) I'm a nervous mechanic, is this something that I should consider doing myself? I'm not bad at working on the truck, I just don't want to screw this up!
4) Should I use isuzu thermo, or is a parts store ok?

Any and all help is appreciated. I saw dub said he wouldn't charge less than 300 for the labor,
So I'm guessin, taking my time, I'm looking at 10 hrs to replace the thermostat?
Any confidence builders reading this? Lol

Thanks!
David

[IndianaVX]

I guess I should add....
When I'm driving, I'm running hot, past halfway on the gauge. If I stop, temp goes up uickly
The only way of keeping needle pointing strt down is to run heat full blast, but even at idle with heat on, the needle get close to pegging it very fast.
Not running ac either. Haven't checked fan clutch yet, but the uppuer hose is hot, and very hard with pressure,
The passenger side hose I can at least s ueeze a little, bot doesn't seem to have fluid in it.
The resivour is full, and when I shut off motor, a couple of air bubbles come from the hose comming from radiator to resivour.
That's all I can think of now
Thanks again folks!
David.

Oh, I did forget....when I first discovered this tonight, I let the truck cool for about 10 min. Then I slowly released the radiator cap to take a look
Inside, and there was coolant present, covering the fins, so I started the truck to see if the coolant would go down
In the radiator so I could add more. Well after about 30 second at idle, coolant came gushing out of the filler hole, pulses of coolant!!!
I uickly shut it off, put the cap on, and here I sit.

[PK]

Your last post makes it sound like a blown head gasket or cracked head.
It would appear that you have combustion gas in the cooling system.
Check and see if your oil is milky, although that normally only happens after days of driving like that.

IIRC, the most common thermostat failure is for it to fail open, not closed.
But I might be wrong.

Good luck.

PK

[Ldub]

Yes, the intake (common chamber) has to come off to replace the thermostat.
The replacement I got from Merlin came with a new O-ring. (the only gasket in this app).
If you do go in after it, be aware of the hard (metal) water pipe that connects to the back side of the thermo housing. You have to unbolt it from the block & carefully wiggle it back out of the housing.
It is sealed by an O-ring that's easy to nick, & you will never know until it's all back together & you're adding coolant...it's a real pisser...
I repaired my FUBAR with hi temp RTV & it's still holding after 2+ years, but I also have some spare O rings from Merlin on board...if I can find them...
Also, if you end up pulling the intake plenum, you might just as well replace the intake gaskets & make sure to torque them to 13 ft. lb., might wanna check the shop manual for torquing sequence...

Good luck with this David, you seem to have had more than your share lately...

[CrossRider]

I just went though this because I blew a head gasket. But I believe it was caused by the O-ring seal on the pipe that runs from behind the thermostat housing. First you need to replace both O-rings for both of the pipes that run to the heater core. Next I would do a compression test to make sure you don't have more wrong than just a bad thermostate if this is the problem.

But if everything is ok on the compression test, you can get a thermostat at NAPA that is the exact match of the one that comes in the car. Next if you haven't got your gaskets I would recommend getting a set (of intake) from BAP auto parts or from Rock Gasket's part # IG353. They are thicker and better made that the others I have seen. The thing is I clipped the O-ring and had to do it twice, so go rent a pressure tester and plug off the hoses coming off the steel tube going to the heater core and make sure the O-ring is in stalled correctly. Or you might find yourself doing it again.

[IndianaVX]

UPDATE
what seemes to have been the problem, was a belt tensioner pully? the day after all the overheating, i pulled into a job, and was making a right turn, and all of the sudden, my steering got very hard to turn. i popped the hood, and my serp belt had come off the pullys! so looked around a bit more, and the whole pully on the belt tenioner had hollowed out, and was just dangling. it was at an odd angle, and had cut a grove in the housing thast the bolt screws into. so my thinking is, that the belt was not spinning consitantly enough to keep the fan spinning, and things pumping.
replaced the assy. and have not overheated since.

does that make a lick of sense? i was really dreading replacing that thermostat. lol....but i do enjoy working on the vx. so its a give and take thing!

[Ldub]

Glad you got that sorted......

[etlsport]

Yea sounds possible. I would think your charging light would have come on too if it wasn't tight enough to turn the water pump