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My motor is running hot. Thoughts??? Update, I was right...


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Sorry, this is going to be another long post...

 

A little background... Back in winter earlier this year, I was having a problem with the coolant not heating up enough. I changed out the 207⁰ thermostat to a Motorad 194⁰ thermostat and it's been fine ever since. The gauge on the cluster would get up to the 210 mark in reasonable time and stay there rock solid.

 

Less than 2 weeks ago, the truck was at the dealership to have a leaky upper oil pan gasket replaced along with leaky transmission cooling lines. I drove it last weekend but didn't seem to notice any major issues. But don't drive much so it was parked for almost a week after that. One thing I did notice while leaving dealership was that it seemed like it was being held back. It's kind of hard to explain but it seemed like it took a little more umph to get going. It's like the motor is straining a bit and under load pretty much all the time. It will still get up and go but at regular cruising speed, it just feels off.

 

I drove it this past Friday and Saturday and still seemed fine.  Yesterday though (Sun), truck had sat overnight and I had to go out. The motor ran for a couple minutes before I drove off. Normal outside temperatures (just over 60⁰) and I happened to glance at cluster about a mile down the road and noticed the coolant gauge edging up to the first hash mark after 210. A couple more miles down the road, I decided to stick in my OBDII reader so I could monitor some different things. The coolant temps would jump up to 220 when running highway speeds but then drop back down after a bit and run between 205 and 210⁰. 

 

Today though, it stayed around 210 after it warmed up and then when I started running down highway (70-80mph) at one point jumped up to 230 and after a bit dropped back to around 215-220. At this time I also noticed that the oil temps were up a bit as well. They usually come close to the coolant temps. At one point, engine oil temp was at 230⁰. All of this was happening with outside temperature of 77⁰. So it really wasnt hot weather. The trans temperature was also running 165-170⁰ and I installed the updated trans thermostat some time ago. 

 

When I was on the way back home, just for kicks,  I wanted to see how it ran without the Range AFM disabler. I noticed that it didn't go into V4 anywhere near what it normally would. It seemed like the only times it would was when I was going downhill on an obvious hill with my foot off accelerator. On flat parts where it would normally go to V4, it would stay in V8 unless again, I took my foot off accelerator. As soon as I touched accelerator, it would jump right back to V8. Another thing I noticed was when taking my foot off the accelerator, it seemed to decelerate a lot sooner than it should. It wouldn't coats at a steady speed and would drop as soon as I took foot off accelerator. Coolant and oil temps continued to stay a bit high even without the Range disabler. At one point, I pulled off highway to check brake rotors to see if there was any heat like a pad dragging. All seemed normal and I could touch each one. I also popped the hood and coolant was fully filled. Gas mileage still seems to be about normal. 

 

So could there have been a problem with anything when either the upper oil pan gasket was changed or transmission cooling lines changed to cause what I am experiencing? It's just odd that it started after all this work was done. Or is this just my imagination and everything is just fine? My gut says that there is a problem but Id appreciate any thoughts on this...

Edited by mikeyk101
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3 minutes ago, m3n00b said:

Almost sounds like the parking brake is in or something else is causing drag in the drivetrain.

 

I normally don't use it that often and there is no "BRAKE" warning light on dash. Funny thing is just 3 nights ago (Fri nite), I did use it for the first time in forever as I was parked on a steep downhill spot but I was already having the problems prior to that. I guess it couldn't hurt though to push it on and off a few times.

 

Also wouldn't the rear rotors heat up considerably if the parking brake was dragging?

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You might be onto something and now I think worth looking into. I just went out there and activated the parking brake a few times and it was creaking something awful. I had drivers door open when I did it and it's pretty quiet here where I'm at. At the very least, it seems that it needs some lubricant on it. I know I've never done it before.

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Well I haven't gotten around to checking further into the parking brake because another issue popped up and I had to work on the bike. Nice weather you know...

 

But tonight I did an unscientific type test. Over the winter, my original thermostat went bad and needed to be changed out. I ended up installing installing a motorad 194⁰ one. Tonight, 82⁰ out. I started up the motor and let it idle. It ran for a bit and I monitored the coolant temp via my OBDII device. I also kept grabbing onto the hose that runs from the thermostat to the radiator. I assumed that I would feel it stating to get warm when the coolant temp was near 194⁰. Nope. I also was occasionally putting my hand on the hose that ran into the water pump I believe??? It was the hose that runs underneath the thermostat. That hose got quite warm. I continued to watch coolant temp rise. I finally shut the motor down when it hit 221⁰. I still never felt that other hose warm up. The radiator was also cool to the touch. 

 

So am I safe in assuming that my newer thermostat is probably stuck closed?

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That's kind of what I was thinking too. When I installed the Motorad 194⁰ thermostat, it was recommended by another member here. But over last couple of days, I have seen that the reviews on that brand are not good and reliability seems to be an issue. I'm not interested in going back to a 207⁰ OEM because I do some towing and want to keep a cooler thermostat. I remember seeing @Grumpy Bear talking about a 174⁰ one from Katech and that it does not require tuning like a 160⁰ one would.

 

https://katechengines.com/i-30497645-kat-a7260-174-degree-gen-5-lt-thermostat.html

 

174⁰ would be better than going back to 207⁰. It seems like the Motorad one used an OEM housing, so would I just be able to buy the Katech stand alone thermostat and swap it into the Motorad housing?

 

Unfortunately when I changed the OEM thermostat, I threw the entire assembly out so I would have no choice but to use the Motorad housing. And ordering direct from Katech seems best as they would be the closest to Wisconsin to get it the quickest.

 

Any other ideas or wothwhile alternatives on thermostats would also be appreciated.

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40 minutes ago, mikeyk101 said:

It seems like the Motorad one used an OEM housing, so would I just be able to buy the Katech stand alone thermostat and swap it into the Motorad housing?

 

Should be a simple element swap. Housings should be identical.  

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I just found an OEM with a slightly lower temp at a reasonable price and get it in a day or so. Part number 12674634. Specs are a bit hard to find but looks like it might be a 195⁰ temp. My original lasted for over 6 years where this Motorad seems to have failed within a couple months. I'm thinking give OEM one more try and worst case, then swap out to the Katech one. I just really wanted something in a lower temp than the factory 207⁰. Nice thing is it's a fairly simple task and can be done in about 15 minutes or so. 

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I thought there was a lower temp option OEM thermostat.  Looks like you found it.

 

I have a Mishimoto 180 in mine.  So far so good  The Mishimoto's in my Duramax lasted many years and are still in there.

 

Scanner shows 177-181 operating temp.  I bought another one for a spare.

 

 

 

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Well my hunch was right and Motorad thermostat must have been stuck. I found the replacement in Amazon in a "Like New" warehouse deal. I figured if it looked hinky, I could always return it. Besides part number 12674634, it also goes by 15-11113. It cost me just over $36 shipped. It came in the proper GM AC-Delco box taped up and truly looked like new. Part number was embossed on side of plastic base and matched.

 

Swap out didn't take long and after buttoning everything up, started motor and let it warm up. It slowly climbed to 194⁰ at which time the upper hose between thermostat and radiator got very warm quickly. Coolant temp on the torque app then dropped down to 186.8⁰ and settled back at 188⁰. 

 

So looks like I'm back in business again. I did save the Motorad thermostat housing this time in case I ever decide to swap out thermostats again. I didn't go for a drive yet but I fully expect to see much cooler temps than I was getting.

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  • mikeyk101 changed the title to My motor is running hot. Thoughts??? Update, I was right...

I still need to look further in the motor seemingly being under load while driving though. The parking brake does seem to fully release by putting truck in drive and releasing the parking brake. It pulls away normally. I don't hear any unusual rubbing or feel anything. We shall see and I will update after next time out and about.

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37 minutes ago, Grumpy Bear said:

Caliper pins stuck dragging a puck? 

I did check all the rotors by feel after running down highway for about 20 miles and none of them were hot to the touch. I would suspect if one of the calipers were stuck or pad dragging, the rotor would have been hot. I would suspect the one of the rear rotors would have also been hot if the parking brake shoe was dragging. 

 

I will see how it goes on my next trip out and report back. I don't drive nearly as much as I used to. Most of the driving is over the weekend and I left it parked this past one because of running hot and used my trike instead. Maybe now that the thermostat has been swapped, it will be back to normal and maybe the truck performance was just my imagination???

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I got a chance to run out for dinner and grocery shopping. 80 degrees outside. I did a 15 mile run down some back roads with an occasional stop sign. Steady speeds of around 60mph. This time it did go up to first to 198⁰ before dropping down to 192 while cruising. It only rose again after stopping for stop signs and then accelerating again. Only once did it go up to 202 when accelerating but dropped back down. Engine oil temp never came close to breaking 200⁰. Once close to destination in some stop and go traffic, coolant temp did rise to 204 but not long and dropped south of 200 quickly. Trans temps stayed pretty steady in the low 150's once heated up. 

 

And the truck seems to be back to normal again as far as handling. I find it hard to believe that a stuck thermostat would cause the engine to feel like it was straining and under constant load but I guess anything's possible. I have a much longer trip traveling mostly on highway on Thursday and curious to see how it handles that but so far, this lower temp thermostat seems to be doing its job. I'm really interested to see if it makes any difference the next time I tow my toy hauler as well. I'm guessing it will be an improvement there as well.

 

And I was able to find out that it's actually rated as a 90⁰C thermostat which is also 194⁰F. It's listed for the 6.2L motors in several years of Corvettes, Cadillac CTS, and Camaros just in case anyone was curious. 

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