98 GMC K-1500 Temp is fluctuating

[Sutty]

I am going to throw in a new thermostat. I haven't put one in my truck before. Assuming I follow the big coolent hose to find it am I right?

Thanks

[Valv]

Yes Sir, follow the big top radiator hose. Usually on Chevy trucks is a very simple operation.

[gunflint]

Did mine last week. It took about 15 minutes

[upnorth]

Just be sure to make sure the surfaces are real clean when you put things back together. Otherwise gaskets fail at the most un opportune time

[ccarlson]

You'll want to suck out some of the coolant with a turkey baster or something before you take off the old thermostat. Otherwise you take off the old thermostat and coolant goes all over since the thermostat is just a bit lower than the top level of the radiator. Squeeze the main hose going to the theromstat to get the coolant out of it too.

Use a clean plastic jug to keep the coolant in and then you can put it back in when done. I suppose you could just drain part of the radiator but sometimes that isn't convenient to get to without making a mess either.

ccarlson

[Sutty]

Thanks for the tips. I need to get r done before deer camp opens...

[gunflint]

Be carefull. I forgot to mention that after I changed the thermostat, I put about 30 gallons of fuel in and put the new 07 tags on. Then on the way to town the tranny went. You just know that this is all related.

[Jeremy airjer W]

Are you sure its just not low on coolant. I would check around the intake usually right where it meets the head. These are real common gaskets to leak. Also there is a quick connect fitting on the passenger side of the motor (if I remember Right) these are prone to cracking and leaking.

Then again it could just be the thermostat. Tyoically they just stick shut or open thats the only reason I questioned it.

Also If the vehicle still has dexcool (GM exteneded life coolant) now would be a good time to flush it out. Especially if the vehicle has been run low on coolant or if the vehicle is nearing the expected life of the coolant. These systems can be converted to the regular (green) coolant to save you a few bucks and with out any ill effects (would highly reccomend using a flush machine to do the conversion, Dexcool and regular coolant DO NOT mix well!!!)

Have fun Sutty!!

[Sutty]

I had it flushed twice last year with the green stuff in. First time it didn't seem to clean it all out ended up with some brownish colored coolant. It has stayed green this time... It is a little low right now. I checked it after a twenty minute drive and it is about at the cold level in the resevoir.

[Sutty]

I brought it in yesturday and had it pressure tested. They didn't find any leaks, they suggested bringing it in cold next time maybe it will show than. I didn't do the thermostat yesturday since I was sitting in the shop. Going to put it in today in the daylight. Probably lose all my coolant on the way to ortonville tonight....

[sparkyaber]

what Airjer said, my '98 with 140000 started to fluctuate badly, check coolant, a little low, checking around under the hood an noticed a little coolant around that intake on the passenger side, grabbed the hose, and boom! that fitting disintigrated. Of course under pressure. Very bad design. It took many hours to remove all of the pieces of thread left in the block. Fun times.

[FISHINGFARMER]

Also check and make sure the sending unit wire isn't exposed to a warm part on the motor. Had that happen one time also, was resting to close to the motor making the temp guage act up. More than likely it's just needing a new thermostat.

Good luck in your repair.

Farmer

[Jeremy airjer W]

sparkyaber, they make a tool for removing those broken of ends. I believe its made by lisle. Costs about $8 and saves about an hour and a ton of grief.

If only you knew then what you know now!!

[sparkyaber]

Now you tell me . Wish Toyota made an extended cab long box.......

[Sutty]

Thanks for the tips. So far it is holding steady. I replaced the thermostat last friday (three trips to the parts store....) The guy had a pretty good laugh at me. 1st trip was for the thermostat second trip was for a deep socket my deep sockets were not quite long enough to grab the nuts... than the third trip was to get a smaller socket I thought I needed a 9/16 and it was 1/2

[Jeremy airjer W]

Sutty, I think those are metric bolts - 13mm I believe.