Thermostat #3 rant

bugnout · **Posted:** Fri Dec 21, 2012 11:28 am

First real winter storm yesterday, Thermostat having a hard time keeping the engine temperatures up. Heater alternately blowing hot and cold, seems independent of the temperature gauge.

Not sure If I'm going to order a stock one or try an inline thermostat. Hate to spend money on a part I know will fail in 30k miles. I'm on the list for Mark K's thermostat, but don't think I'm going to make it thru the winter on this one.

This tstat design just pisses me off.

4x4kingx889 · **Joined:** Sun Jul 17, 2011 6:42 pm **Posts:** 235

Im on the same page as you I had the inline one but I just bought a new one from mopar it at idle or going down hills the temp drops I don't know what else to do :?:

arengant · **Posted:** Sat Dec 22, 2012 2:16 am

You could always move somewhere warmer

striperman36 · **Posted:** Sat Dec 22, 2012 6:25 am

Get a dia winter blanket to block the grille, I have mine on and it really helps keep it at operating temps

racertracer · **Posted:** Sat Dec 22, 2012 6:26 am

bugnout wrote:

Heater alternately blowing hot and cold, seems independent of the temperature gauge.

I experienced the same thing just before my 1st head gasket failure and the temp gage was reading correctly, it didn't fluctuate, same as yours is doing now.

I believe that the issue you are having may be trapped air in the cylinder head.

1st. make sure that the small 3/8" dia. hose leading from the top of the radiator isn't clogged. This hose is the one that leads to the left side of the expansion tank, it is the hose that lets the air escape.

Not sure why it happens but you got to get the air out and opening the vent on top of the radiator doesn't help, it doesn't get the air out of the head, it may be because the opening may be at the same level as the head or lower, I don't know. I just know from experience that it doesn't work.

2nd. If you have time, try replacing the new thermostat with the old one and see if the heater begins to work again. It may be that the new thermostats are malfunctioning right out of the box, Who knows?

It is imperative that you find a solution before your head overheats. I'd stop using the vehicle.

This is what started my head gasket problems and the reason why I dread replacing the thermostat.

Be very careful with it, is not something I would take lightly and I would solve this problem before bringing the engine up to high operating temps.

Also, my diesel mechanic at the Jeep dealer, told me that there is only one way to properly replenish coolant on this engine without getting air in it, open the petcock at the bottom of the radiator and remove the cap on the top of the expansion tank allowing the coolant to fully drain out of the system, then close the petcock and refill it from the top, never opening the vent on the radiator. Opening that vent allows for the radiator to fully drain but minimizes the natural downward flow of coolant from the rest of the motor.

The coolant has to flow from the top down and the air has to escape through that 3/8" hose leading from the top of the radiator to the left side of the expansion tank while it is being filled. This is the only way to properly change the coolant.

There have been other members who have experienced this same scenario after replacing their thermostat and just one other member that I heard from who experienced head gasket problems and believes it was due to the thermostat replacement.

I will be watching this thread intently, hoping that you find a solution, keep us posted.

naturist · **Posted:** Sat Dec 22, 2012 10:27 am

Back in the late 60s I owned a BMW (car) that used a thermostat of this design; that is, it was a T shape and mixed outgoing heated coolant from the head with cold coolant from the radiator to supply constant temperature intake coolant to the water pump. BMW said they used that more expensive design because it warmed the entire engine up more quickly and evenly and prevented cracked blocks from working the engine hard in freezing weather.

In BMW's design and execution, it worked well and was essentially bullet proof. Which it may not be in Jeep's implementation. To be sure, the OP's thermostat needs to be replaced. No, it won't last the winter.

The common thermostat works by simply blocking the flow of heated water from the top of the head. We've plenty of evidence of what happens when these engines overheat: a blown head gasket and likely cracked head are the common result. This happens because the head is aluminum and the block is iron, and the two metals expand from heat at different rates. It appears to me that the standard water-block type thermostat would make that very damage more likely, by trapping hot water in the head while the block is still cold. Thus I am not excited by the prospects of saving about $100 on the cheaper inline thermostat at the increased risk of a cracked head. The head is too expensive to replace if I'm right about the increased risk.

B99 · **Posted:** Sat Dec 22, 2012 10:50 am

I had some blockage in the heater core. engine temp was good but min heat out of heater. The hose coming from the viscous heater would get hot but the return line from the core would cool off fast if the fan was above 1. Drained about a 1 1/2 gal from radiator, disconnected both 5/8 hoses, stuck a nipple and garden hose into the return hose from heater core and slowly ran some water through backwards. There were some deposits that came out. reversed nipples and ran some through forward and then backwards again. It now has heat which is good considering its been in the mid teens at night in n. utah. I dont thing its as hot as it used to be but it at least gets the cabin warm now. I will do another flush and reverse flush when I do the tbelt & water pump this spring.

papaindigo · **Posted:** Sat Dec 22, 2012 11:11 am

That clogging has been reported before and seems to often be associated with mixing in non-spec coolant. Use only HOAT coolant and if anything else has been used in the system do a good flush and install 50/50 HOAT. Note a simple drain won't get all the coolant out of the system due at least in part to the location of the lower radiator hose. I "think" but have not tried it yet that the Prestone flush and fill kit will allow flushing all the old coolant out. Otherwise do repeat drain, refill with demineralized water, do a short drive, drain until the drained fluid is essentially clear which is good enough.

LIBERTYinLIBERTY · **Posted:** Sat Dec 22, 2012 2:37 pm

I just replaced the Murry in line I put in last year, went bad, just put in the Stant 13519 195f Thermostat, works like it should now.

bugnout · **Posted:** Sun Dec 23, 2012 12:01 pm

arengant wrote:

You could always move somewhere warmer

Someplace like Hawaii would probably do

bugnout · **Posted:** Sun Dec 23, 2012 12:12 pm

Thanks guys,

This thermostat has about 30k on it. I did a complete coolant change this summer, drained and filled with distilled water, drove it for a week then drained and filled with the proper mix of Zerex. I pretty sure I got all the air out, took a couple of weeks. I've never seen a temperature spike, and I'm the only driver. Have seen the temp go over normal when towing but not since I changed out the fan clutch and fan.

I think the thermostat started going bad this spring (before the coolant change) when I started to have an issue with the coolant overflow not getting sucked back into the tank when the engine cooled. Interestingly, I no longer have that problem, but now the needle is half a tick left of where it should be, plus the new symptoms revealed when it got cold.

I think I'm going to try the inline Stant and see how well that works. Will have to wait till after the new year to dig into that.

arengant · **Posted:** Sun Dec 23, 2012 3:04 pm

Even with my Hayden and nylon fans I had a temp spike with an inline t Stat. Be careful

nissanfrontier · **Joined:** Tue Dec 22, 2009 4:09 pm **Posts:** 145

Could be your heater core is plugged. Mine was and had correct HOAT in there It was past it's time though. Get you some extra hose at parts place mine was 2 6 footers. Disconnect 2 go into stock thermo area. There is in and out for heater core great spot to hook up. I hooked 2 long hoses up here. With adapters and such got my garden hose hooked to my hot water heater in basement. With helper have them ram hot water on and off try clear it out. Then gently blow out core. Pour rad cleaner in there let it sit 30 minutes, then get hot water in there clear it out. Mine works great now I got heat. Cleaner out my whole system in summer with rad cleaner filled back up with NAPA clear HOAT in Gold bottle.

Ditto on not being excited about inline, just posted a question about correct position. Everyone installing there's backwards?

arengant · **Posted:** Wed Dec 26, 2012 7:05 pm

nissanfrontier wrote:

Could be your heater core is plugged. Mine was and had correct HOAT in there It was past it's time though. Get you some extra hose at parts place mine was 2 6 footers. Disconnect 2 go into stock thermo area. There is in and out for heater core great spot to hook up. I hooked 2 long hoses up here. With adapters and such got my garden hose hooked to my hot water heater in basement. With helper have them ram hot water on and off try clear it out. Then gently blow out core. Pour rad cleaner in there let it sit 30 minutes, then get hot water in there clear it out. Mine works great now I got heat. Cleaner out my whole system in summer with rad cleaner filled back up with NAPA clear HOAT in Gold bottle.

Ditto on not being excited about inline, just posted a question about correct position. Everyone installing there's backwards?

You found NAPA branded HOAT coolant? Or bought Zerex G-05 from NAPA?

CRD05il · **Posted:** Wed Dec 26, 2012 9:15 pm

My in-line work's great I would just check to make sure it work right on the stove before you put it in. A few people said there's didn't open all the way. I did it to mine from the beginning and it works great in the Chicago weather.

Thermostat #3 rant

Who is online