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01 4.0 thermostat - check ball?

B

BMWGuy

NAXJA Forum User
Location
Columbus, OH
2001 XJ Sport, 126,000 Miles - cooling system all original.

No issues, just wanted to start doing some preventative maintenance and a coolant flush.

I had already bought Autozone hoses and a thermostat. Pulled the OEM thermostat and it has a check valve/ball at the top. The Duralast doesn't. Can I drill a small hole or just go to the dealer?

I did a forum search and came up with the standard definitive answer - yes and no (on the Jeep OEM replacement). I also put the lower hose in without the spring. I tried to get it in the new hose but could get it in properly.

If I go to the dealer for the stat I might as well get the hose also.
 
I like to use a dealer T-stat, seems to make a difference 'burping' the system, and keeping it burped. There is a major flaw with the XJ's cooling system, in that the radiator cap is not the highest point in the system, the T-stat housing and upper hose are. The check ball lets the air bubbles that collect pass the T-stat, until it's warm enough to open. Some XJs operate fine without it, but my '96, when warming up, would spike rather high, then settle down. Dealer T-stat, and all is well! Just my $2.00-($.02 adjusted for inflation!).
 
I'm not familiar with Duralast but to answer your question, yes you can drill a small 1/8th inch hole on the top (12:00) of the stat. I like stats bought directly from Jeep and also the Stant SuperStat is good.

Best to have that lower hose spring installed. They can collapse.

Hoses are a cheap insurance on an overheat and with a 2001, you do NOT want an overheat as the "infamous" 0331 cracks easily with a single overheat. Be sure that you replace all hoses, including heater hoses.

Also you should replace the radiator cap. Another $5.00 well spent and if it is the original, it is time for it to GO.

And when you get to either water pump and or radiator, do em both while you have things apart. Parts aren't that expensive and if you do the labor yourself, it is again....cheap insurance against an overheat.
 
Re: 01 4.0 thermostat - follow-up

I looked at the Stant on-line and at the auto parts store but I didn't see the bypass. An on-line spec said it didn't have a "water outlet". Not sure if that is the same as the check ball/bypass.

So, I just got an OEM thermostat. The original lasted a long time so I don't mind OEM even though I prefer aftermarket stuff.

Dealer wants $65 for lower hose and they didn't have it in stock. I just reused the original spring in the aftermarket hose and it worked fine. Everything is back together and seems to be OK. Runs a little cooler too. I had a feeling the original stat wasn't working very well.

Next will be the radiator and water pump (in the Spring when I also put the Crown Vic rear discs on the back).

And, a BMW isn't any more difficult to more on than a Jeep. Or, maybe I just suck at being a mechanic. :laugh:
 
heyhar said:
I like to use a dealer T-stat, seems to make a difference 'burping' the system, and keeping it burped. There is a major flaw with the XJ's cooling system, in that the radiator cap is not the highest point in the system, the T-stat housing and upper hose are. The check ball lets the air bubbles that collect pass the T-stat, until it's warm enough to open. Some XJs operate fine without it, but my '96, when warming up, would spike rather high, then settle down. Dealer T-stat, and all is well! Just my $2.00-($.02 adjusted for inflation!).
Click to expand...
Yeah... the I6 didn't fit too well into an engine bay originally designed for an I4 or V6, I guess. Always wished it did.

I am running a DuraLast in the MJ, seems to work fine so far. If it fails I will put in a Stant for sure, I used it because I bought it years ago and lost the receipt, and had it around - and when I needed to install it, the parts stores were closed.
 
I noticed some very minor differences in the aftermarket hoses but nothing to be concerned about. Nice thing about a lot of BMW parts - I can buy OEM manufacturer stuff from aftermarket sources at pretty decent savings so I know the parts are correct. Don't really know about Jeep parts.
 
An alternative to the lower hose spring combo is the UNIVERSAL hose with the spring built in.
 
Not trying to jack your thread, but I have a question dealing with my thermostat and just by reading this answered one question but I still have another. Hope you dont mind.

Today I replaced my stat with the duralast one which I now know isn't the prefered and after I tightened the housing back up I poured some coolant into the radiator house, and it started leaking out of the thermostat housing by the bottom bolt. I thought it wasn't tight enough so I cranked it down and I freakin cracked the housing. I got a new one, did everything over and It still leaked. Whats the deal? What can i do to fix this?
 
hopper720 said:
Not trying to jack your thread, but I have a question dealing with my thermostat and just by reading this answered one question but I still have another. Hope you dont mind.

Today I replaced my stat with the duralast one which I now know isn't the prefered and after I tightened the housing back up I poured some coolant into the radiator house, and it started leaking out of the thermostat housing by the bottom bolt. I thought it wasn't tight enough so I cranked it down and I freakin cracked the housing. I got a new one, did everything over and It still leaked. Whats the deal? What can i do to fix this?
Click to expand...

I would suspect that the mating surface on the head is not clean--it just take a small piece of gasket left there to cause this problem. The other usual culprit in this is the thermostat flange has slipped down and is caught between the housing and the mating surface.

My old school thermostat procedure is to clean both mounting surfaces completely. Then I put a little Permatex non-hardening in on the thermostat housing, including the recess for the thermostat flange. Stick in the thermostat, then press the gasket into place, leaving the engine mounting surface and that side of the gasket dry--next time it will make cleanup easier. Then bolt it up, making sure to use the short and long bolts in their proper holes.

Good luck.
 
I used a gasket from Autozone. It has a bead of sealer on it. I tightened the bolts to 15 ft-lbs per the manual. No leaks. But as joe_peters said, the mating surfaces have to be clean. I spent a lot of time with a razor and gasket scraper to remove the old gasket. Then I used a sanding block on the head and housing to make sure everything was smooth.
 
hopper720 said:
Not trying to jack your thread, but I have a question dealing with my thermostat and just by reading this answered one question but I still have another. Hope you dont mind.

Today I replaced my stat with the duralast one which I now know isn't the prefered and after I tightened the housing back up I poured some coolant into the radiator house, and it started leaking out of the thermostat housing by the bottom bolt. I thought it wasn't tight enough so I cranked it down and I freakin cracked the housing. I got a new one, did everything over and It still leaked. Whats the deal? What can i do to fix this?
Click to expand...

I coat the gasket with a super thin layer of gasket sealer on it. In my experience, if the gasket sealer is any thicker than a sheet of paper then it will not seal reliably. Use a wire brush to get the old gasket off. Make sure to use gasket maker on the entire surface. Don't over coat it. Remove all the excess by wiping across the gasket. The bolts don't need to be super tight.
 
I'd go with the OEM hoses; even if you have wait to buy them on line, if price is a factor. At one time I had bought some aftermarket hoses, and the fit (as far as the molded bends) was marginal at best. Particularly where the upper hose routes around the battery.

The after market hoses were an awkward fit, and soon began chaffing at the corner of the battery. I put some foam in the problem area (which looked like ass) until I was able to replace them with OEM hoses. The fit is so much better and worth the price for peace of mind...
 
The lower hoses I get from CarQuest fit just fine, though they come without the spring.

If you can get a hold of the end of the spring in the old hose, don't just pull on it, try winding the coil a little tighter while pulling gently and the spring should come right out.

You can then insert it into the new hose using the same technic........ Easy.
 
joe_peters said:
Don't drill the thermostat. Return it.

Purchase a Stant SuperStat Premium and install it. It has its own bypass built in and is better than that Duralast stuff.

Stant: http://www.stant.com/brochure.cfm?brochure=205&location_id=168

I don't recommend and I won't install anything but these.
Click to expand...

Joe, these work great but I don't recall them being designed for bleeding air through at the top like the OEM.

Isn't that v-notch (bypass?) more about coolant flow and not necessarily the trapped air in the system?

What about drilling a small (3/32") hole in one of these?? Think it would affect it much???
 
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