Inline thermostat issues

arengant · **Posted:** Mon Jun 13, 2011 12:13 pm

My stock thermostat was stuck open/partial open. Ambient temps never fell too far below freezing this last winter here in the PNW so my temp. gauge hovered around the ¼ mark. MPG dropped (also winter fuel) so I decided to get the Meziere housing and give it a go. Before I installed the thermostat, my gauge was about half way between ¼ and ½ ticks on gauge, with ambient air temp around 60 degrees.

Install went easy, used a 195 stat from napa.

So this morning on the way to work, reached operating temp with needle pointing straight up and down. Got on interstate, but when going at appx 5% incline grade the temp started to climb, it actually passed ¾ before I slowed (was going 60 mph, hit traffic went to 40) and it dropped to 1/2 . Fluctuated from ½ - appx ¾ a few times. This I assume is the state opening/closing.

Because I was worried that there might be a problem, I did a few more tries up the same part of the interstate (and steeper) trying to replicate the situation and got better results. By the 4th time, the needle didn’t get passed the 5/8 mark before it opened.

So, it seems the inline thermostat works perfect when the new stat opens, but it doesn’t seem to open fast enough. I’m thinking I should get a better stat? I would say though that once it opened it cooled really fast, so I doubt the inline causes too much restriction for towing/hills.

I am doing a cross county trip next month so I need to make sure it’s good to go. Next is to check the mech. Fan to see if it will engage (by blocking the radiator).

Wobbly · **Posted:** Mon Jun 13, 2011 2:38 pm

Was the radiator vent opened to bled air from the system?

arengant · **Posted:** Mon Jun 13, 2011 6:25 pm

Not since the initial run today, I'll do it once it cools off tonight.

Wobbly · **Posted:** Mon Jun 13, 2011 6:35 pm

You'll get better venting with a warmed up and running engine and with heat or defrost selected and some engine revs. Don't open the reservoir cap with a warm engine .

arengant · **Posted:** Mon Jun 13, 2011 10:57 pm

the small black cap ON the radiator is what you are saying to vent with it warm and running??

It's been running better and I do appreciate the cost savings over the OEM thermostat

Wobbly · **Posted:** Mon Jun 13, 2011 11:00 pm

arengant wrote:

the small black cap ON the radiator is what you are saying to vent with it warm and running??

It's been running better and I do appreciate the cost savings over the OEM thermostat

Yes.

arengant · **Posted:** Tue Jun 14, 2011 12:54 pm

Engine was just barely warm, I opened the vent valve and just coolant came out. I closed it back and kept driving. My thermostat still stuck a little, almost to 3/4 mark before it opened. I will try a new "premium" thermostat and see if that helps.

Again, good concept, the inline thermostat, I just might have picked up a bad one. I will boil test the new one before install.

JL Rockies · **Posted:** Tue Jun 14, 2011 1:10 pm

or you could have one of those CRD's that run hot

papaindigo · **Posted:** Tue Jun 14, 2011 2:18 pm

I may be totally off base but in case I am not. If I understand it correctly the inline tstat is placed in the "big" water line leading from the OEM tstat housing to the radiator leaving that housing and its internal OEM tstat in place. The sending unit for the temperature gauge is on the back (firewall side) of the OEM tstat housing and hence measures the temperature inside the upper part of that housing. If the OEM tstat is performing properly it would reach full open at ca. 176 degrees and pretty much fully divert coolant flow from what I'd call the warm-up circuit to the operation circuit thru the radiator. BUT with the inline tstat blocking the flow to the radiator it seems to me that the inline tstat is going to open "late" due to lack of water flow compaired to the heat rise in the OEM tstat housing hence the in dash temperature gauge is going to peak higher than 176 degrees before the inline tstat opens but once the inline tstat is open things should settle down although there may be some fluctation in temperature reading as the inline tstat pulses open/closed early in the cycle (NOTE both my 1993 and 1996 Dodge Cummins OEM tstats pulsed that way during the initial run to full operating temperature).

If this chain of logic (???) is on point then maybe folks using the inline tstat need to try an old timers trick whose original purpose was to prevent dangerous engine overheating due to a failed closed tstat. The trick is to drill a 1/8" hole in the tstat skirt. In the CRD this would allow passage of some heated coolant to the radiator during warm up and IMHO might serve to transfer heat to the inline tstat more quickly and avoid the apparent heat rise caused by the inline tstat initially blocking circulation.

Thoughts or I am I completely :5SHOTS:

to the wind? Obviously this assumes one can get inside the inline tstat to drill the hole.

arengant · **Posted:** Tue Jun 14, 2011 9:49 pm

papaindigo:

yes the inline goes in upper radiator hose. I did NOT drill a bypass hole, mainly because I forgot

But I thought I read the chevy tstat has some bypass.

I blame the tstat because it ONLY climbs to the 3/4 mark when the engine is cool before I start driving. (IE: in the morning) However, after the tstat has opened and close a few times (seen by the needle moving) all seems normal.

Example: On the way to work up the interstate it will hit the 3/4 mark once, then back to middle within 2 seconds of tstat opening.

A few hours later after letting the engine cool (1/4 mark at start up) I have seen the needle move slightly past center, then the tstat opens.

After parking for one hour, I then drive same hill on interstate the needle doesn't move past center at all. I tried everything I can think of, turning OD off, getting TQ locked at 50 mph then heavy acceralting... nothing moves the needle once the engine has been at normal operating temp. Granted I don't do the grades daily that some of you see in the Rockies, but I do not think mine is overheated.

The dealer wanted 150 to relash me for the TSB! oh well, I have yet to hear my clutch fan engage with normal driving. I am still going to block the radiator.

papaindigo · **Posted:** Wed Jun 15, 2011 9:20 am

arengant - Sounds like the inline tstat works fine once it opens and flow is established which is good. I still am of the opinion that the hole in the skirt trick will help the slightly slow opening assuming there is no bypass already built into the inline tstat.

If you try blocking your radiator to boost coolant temp to see when the fan engages I'd strongly recommend you also have a mechanism to measure actual temperature at the site of the OEM temp sending unit on the OEM tstat housing. Ideally a infrared remote unit; I see some reasonably reliable ones on Amazon for not too much but I bet you can rent one from like Autozone or if you are in good with a local autoshop that has a unit you could do the test on-site. I suggest this so you can also check the calibration on your temp gauge to determine if you have one correctly calibrated for the CRD engine.

As to the STEALERSHIP $150 charge that's outright highway robbery. Mine was done by a dealer for free under the TSB although the service writer did mutter about charging me at which point I stuffed a copy of the TSB in front of him and said the only way I'm paying anything is if the scan gauge indicates no calibration is needed and then I'm not paying $0.05 more than 15 minutes shop time. The TSB is posted at http://www.jeepkj.com/forum/showthread.php?t=27666 as you can see the time allowance is 0.2 hrs or 12 minutes hence $150 is simple outrageous. I'd go on about service writers but it's not worth the bytes or key strokes.

arengant · **Posted:** Thu Jun 16, 2011 8:19 pm

Well I couldn't open the inline housing due to the gasket on the threads. I’ll need two spanner wrenches when it’s time to replace. I did however drill a bypass hole. I reinstalled and drove the same route again.

Without the bypass, the coolant between the block and the inline tstat (about 9 cubic inches!) doesn’t get circulated so it doesn’t reach the temperature required to open the second thermostat. Now, the coolant can flow fast enough to heat up the inline tstat.

The needle no longer passes the halfway mark! BUT the downside, it *edit* takes longer to warm up, to reach operating temps

:oops:

Wobbly · **Posted:** Fri Jun 17, 2011 9:09 am

arengant wrote:

...
The needle no longer passes the halfway mark! BUT the downside, it

You weren't texting while driving when the engine seized on I-5 during rush hour were you?

arengant · **Posted:** Fri Jun 17, 2011 4:10 pm

So to conclude:

Another successful inline thermostat customer. I purchased the Meziere WN0072 Inline Thermostat Housing from Amazon.com 1.5” diameter for 55 bucks.

http://www.amazon.com/Meziere-WN0072-Inline-Thermostat-Housing/dp/B003NDHHAW/ref=sr_1_2?s=automotive&ie=UTF8&qid=1308341131&sr=1-2

Then I purchased a generic 195 degree Chevy thermostat from Napa (used a 1990 Chevy K1500). Before drilling the bypass hole, it took a few extra moments to open fully, causing the temp to spike. I disassembled, drilled a 3/32 hole in the outside edge of thermostat and reinstalled. Now everything works great! I cut about 2” total off of the upper radiator hose, and bought two hose clamps. The whole project can be done in about 30 minutes easy.

*edited for accuracy*

papaindigo · **Posted:** Fri Jun 17, 2011 5:04 pm

Sounds great but isn't that Meziere WN0072 housing 1.5" inlet/outlet which should be fine since the upper radiator hose is about 2"OD. I appreciate the write-up and have saved for future reference just in case.

arengant · **Posted:** Fri Jun 17, 2011 10:11 pm

Yes, thanks again for the correction.

The meziere is for a radiator hose with 1.5 inch inside diameter. I'll edit so not to keep confusing people.

arengant · **Posted:** Wed Jul 13, 2011 10:55 am

Well, did a 2k mile road trip, up over the mountains, avg about 70 mph, NO overheating problems, never passed the halfway mark. Total weight in jeep was 1200 + lbs over empty. No towing though. Looks like the inline is holding in there for me!

dieseldoesit · **Posted:** Wed Jul 13, 2011 11:43 am

Did you notice any changes in MPG compared to before you did the inline thermostat?

Thanks for all the info.

arengant · **Posted:** Wed Jul 13, 2011 4:51 pm

for MPG, I thought I would notice a larger difference, but I only did about two tanks before the trip. It did go up only about 1 mpg, to about 26 mpg over the two tanks of fuel ( combined driving ) I was getting better last summer, dropped through winter which I contributed to a combination of winter fuel and lower operating temperatures. And this summer I have the lift and some armor, so I might not ever get back to my 28 MPG I had last year, unless I get the TCM tune...

My MPG on the trip from WA to MO was about 25 mpg still, I hit 26 mpg never going over 70 mph through OR and ID, but the pass and higher freeway speeds through UT, WY, NE I was getting about 24 mpg.

William Waddy · **Joined:** Mon May 09, 2011 4:16 pm **Posts:** 56

Did you remove the oem tstat? I am currently on a trip in utah and noticed that engine temp is spiking when pulling steep grades. Did not notice problem before other mods including 33" km2's and 4.56 gears, but have also not been on the freeway for a few months. I can only think of the tstat not fully opening that would be causing this problem, and this inline mod is appealing. Just seems like i would also need to remove oem tstat.

Inline thermostat issues

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