Help with a thermostat part #

Alright this n00b really needs some help. I tried searching everywhere and can't find an answer. I am wondering if the Mr Gasket 4365 thermostat will fit a 97 4.0?

I am trying to upgrade the puking coolant system on my XJ and am having a hell of time finding what I need. BTW is the Hesco high flow water pump worth the coin? It costs about twice that of a GMB high flow one does.

Dark Knight said:

Alright this n00b really needs some help. I tried searching everywhere and can't find an answer. I am wondering if the Mr Gasket 4365 thermostat will fit a 97 4.0?

I am trying to upgrade the puking coolant system on my XJ and am having a hell of time finding what I need. BTW is the Hesco high flow water pump worth the coin? It costs about twice that of a GMB high flow one does.

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Measure the flange of the thing - it should fit in the recess. Make sure that the flow area through the valve is roughly the same as well.

The HESCO pump (and most high-flow pumps) uses a "baffled impeller". Water pumps used in engines aren't positive displacement pumps, they're inertia pumps, meaning that there's plenty of room around the impeller. This allows the pump to spin freely when there isn't much circulation - like when the thermostat is shut.

A "baffled" impeller is pretty much an impeller that has a baffle plate on one side, turning the impeller vanes into scoops. This allows the pump to impart more inertia to the circulating fluid - which can increase flow rate (when there is potential for flow - i.e. the thermostat is open.) However, it still won't be "positive displacement" - you actually don't want something like that when the flow can be shut off, or you'll blow out something important.

However, it's easier to try to fix a problem when one knows what the problem is. What are the symptoms, and what have you done to try to fix it so far?

This thing has a whole lot of issues but right now I am just dealing with the cooling and the leaking.

It's biggest issue is that it, at random, dumps a crap load of coolant out from around the pump housing. I am not sure why but some days it is just a trickle and other days it empties the reservoir bottle. In addition to that it also likes to overheat (with plenty of coolant in the system). Although that is based off how hot my feet are getting not off the temp gauge, which only seems to work when it wants too. I am thinking that some of the overheating is the result of a sticking thermostat because some days its temp will skyrocket faster then I can crank the heater to max.

So since the ol' girl is closing in on 200k, I decided that I would try upgrading the water pump, thermostat housing, and thermostat and replace all of the hoses and the temp sensor. Hesco has a fancy water pump with a CNC'd impeller but I am cheap bastard so maybe I will go with the GMB or Flow Kooler. However, when it comes to a thermostat, for some reason it is damn hard to find a good one.

Dark Knight said:

This thing has a whole lot of issues but right now I am just dealing with the cooling and the leaking.

It's biggest issue is that it, at random, dumps a crap load of coolant out from around the pump housing. I am not sure why but some days it is just a trickle and other days it empties the reservoir bottle. In addition to that it also likes to overheat (with plenty of coolant in the system). Although that is based off how hot my feet are getting not off the temp gauge, which only seems to work when it wants too. I am thinking that some of the overheating is the result of a sticking thermostat because some days its temp will skyrocket faster then I can crank the heater to max.

So since the ol' girl is closing in on 200k, I decided that I would try upgrading the water pump, thermostat housing, and thermostat and replace all of the hoses and the temp sensor. Hesco has a fancy water pump with a CNC'd impeller but I am cheap bastard so maybe I will go with the GMB or Flow Kooler. However, when it comes to a thermostat, for some reason it is damn hard to find a good one.

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Not so on the last - Stant and RobertShaw are both quite good - I've used both brands extensively.

I've not tried the HESCO pump, so I can't speak as to its quality. However, with "open-style" pumps (like we have - you can see the impeller with the pump removed,) I've had good luck boosting pump performance slightly by making my own impeller - use heavy-gage sheet CRES or aluminum, cut it to (or slightly larger than) the OD of the impeller wheel, centre accurately, and rivet in place (use three or four rivets.) Flush to remove drillings and install. But, I've only done this on a few engines - while it did make a difference, I was fighting other overheating troubles anyhow.

Have you a non-contact thermometer? I'd use that to back-check the temperature sensor when it gives a spurious reading - just aim the thing at the thermostat housing (where the sensor is anyhow) and compare. Since OBD-II drives all engine coolant temperature-related functions off of that one sensor anyhow, a faulty reading there will cause you trouble in other places - so it's nice to know.

If the water pump has not been serviced recently, you could have a blown shaft seal - which will give with a coolant leak after shutdown (a failing gasket usually leaks all the time, while a shaft seal usually lets go once circulation stops but pressure is maintained. It's funny that way - and it's a "beginning failure." Sooner or later, it would just fail entirely and leak coolant all the time.)

Drill the thermostat so it will purge air (I've covered this plenty of times before, specifically for RENIX, but it will help on pretty much anything...) because you can often get an air pocket trapped behind the thermostat that will cause you all sorts of headaches.

Those are my first thoughts.

5-90 said:

Not so on the last - Stant and RobertShaw are both quite good - I've used both brands extensively.

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I know those are good, my problem is that I can't find anyone that actually carries a good balanced thermostat for my Jeep. I must be a raging idiot because I haven't been able to find one after numerous internet searches and numerous calls to local parts stores. The Mr Gasket one I was asking about is suppose to be a re-badged Robert Shaw.

I did a search about the thermostat drilling and dang is that a controversial subject, but I think I will give it a try.

I also don't have an IR temp gauge laying around but my work has one if I need it. So far when the temp gauge starts bouncing I use the ultra precise hand-1"-over-the-thermostat-housing method.

And I doubt this thing has ever had anything on the coolant system serviced besides the coolant itself. What you are saying about the pump shaft seals sounds exactly what is going on though. I just hope that the parts I am getting solve the overheating and that the craptastic rad is still good.

Dark Knight said:

I know those are good, my problem is that I can't find anyone that actually carries a good balanced thermostat for my Jeep. I must be a raging idiot because I haven't been able to find one after numerous internet searches and numerous calls to local parts stores. The Mr Gasket one I was asking about is suppose to be a re-badged Robert Shaw.

I did a search about the thermostat drilling and dang is that a controversial subject, but I think I will give it a try.

I also don't have an IR temp gauge laying around but my work has one if I need it. So far when the temp gauge starts bouncing I use the ultra precise hand-1"-over-the-thermostat-housing method.

And I doubt this thing has ever had anything on the coolant system serviced besides the coolant itself. What you are saying about the pump shaft seals sounds exactly what is going on though. I just hope that the parts I am getting solve the overheating and that the craptastic rad is still good.

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If you haven't flushed in some time (it should be done every other year...) get some of the two-step stuff - the first step is oxalic acid (powder,) and you run that for a while. The second step is a neutraliser for the acid - do not forget to run the stuff!

You can also get some of the "seven-hour" flush - put it in, drive around for a day, then flush it out.

Either way, blow the thing good and clean, then refill using coolant and distilled or R/O water in whatever cut is appropriate for your area (ain't always 50/50.) DO NOT USE TAP WATER! Tap water contains dissolved metals and solids, and will screw up your system with deposits. How fast depends on your local water quality and the age of your plumbing (out here, deposits form rather quickly.)

I've never fully understood the idea of a "balanced" thermostat - it's not like it moves or anything, so what's the trouble? It opens, it closes, liquid flows through it. No point in spending money you don't have to.

Also, what's "controversial" about drilling the flange? I've not noted any trouble, the holes are small (typically 1/16" or thereabouts - .0625",) and it does help purge air pockets in the cooling jacket - especially after an overheat or in the event of a head gasket leaking. I've never found a downside to doing it, so I've seen no reason to stop. It's been 18-20 years since I found out about it...

IR thermometers have come down in price as well - there's no reason you can't find a reasonably accurate unit for under $100, and they're quite useful (you can also use them to find out if you have a clogged section in your radiator, for instance.) I'm familiar with the "Boy Scout Hand Thermometer" method - but accuracy suffers due to individual tolerance for heat...