Another 88 4.0 XJ heating up too much

First of all let me say that the advice given by you all has been dead on every for every single question I have asked. Bravo gusy, you really know your XJs!!!! I'm getting there but have many strides yet to make.

Anyway, I was forced to take the wifew out to dinner over the weekend. We made our way to downtown Annapolis, MD in my '88 XJ, 4.0, auto w/ 209K on the odometer. As we are sitting in the midst of the BMWs, Mercedes, Acuras and other what-nots waiting to get into the parking garage, the XJ really starts getting hot. By the time we get to out space, the gauge is reading just about 240 and she (the XJ) was blowing coolant from around the overflow tank. I couldn't tell exactly where it was coming from since it was dark, the underhood light ain't worth nothin' and I didn't have a flashlight.

I spent all of dinner worry about it. We made our way home w/ normal temperatures and increases on when sitting at stop lights. As soon as we got moving again, the temp returned to normal. I am planning a full coolant system flush and refill w/ a new OEM thermostat. The radiator was replaced at roughly 175K. I also noticed that the hoses were somewhat soft so I will be replacing those as well.

My questions:

1. Since the temp goes up only at idle and when not moving, my first thought was to look at the fans (both electric and mechanical) so see if they are operating properly. What exactly should I be looking for?

2. The heater hoses going from the pump oulet (I think) are also fairly soft and old so I would like to replace them as well. I'm guessing this is a dealer only item and I should expect to pay w/ my arms and legs. Correct?

3. Since the radiator is still fairy new, I don't really want to pull it out to perform the swap to an open system yet. Can this be done using a stock radiator?

UPDATE: Just checked out the cooling bottle and sure enough, it's cracked. Can this be the cause of my problem?

Thanks again for any tips you can provide.

Brian

I would say yes.....that could be a major problem. Since you have a closed system, it relys on pressure, with a crack, you are not getting the pressure you need, therefore not proper circulation. Buy one off ebay, replace it(if not already done). While your at it, go ahead with the system flush wit hall new fluid. Run her around see it that worked.

Or give eagle a shout for the aluminum replacement coolant bottle that takes a normal rad pressure cap. He has the part numbers memorized by now.

gw204:

I just recently resolved an overheating problem with my '88 XJ that has been a headache for the last 2 years. Here's some advice that comes from trial and error, both on my part as well many other owners.
* Regarding the thermostat: get the dealer one because it has a hole in it that needs to be installed in the 12o'clock position to allow trapped air to escape – the aftermarket ones don’t have this hole.
* When you flush your radiator, flush it both forward and backwards - from the bottom to the top.
* A filter: Before you put back in the antifreeze fill the system with water. Get some pantyhose and install it where the upper radiator hose attaches to the radiator. Run the Jeep for 10 minutes. You’ll be amazed at the crap that it catches. Repeat several times.
* Regarding the bottle – I found a low-cost replacement at quadratec.com. However, just like the dealer bottle, whenever the bottle is subjected to extreme temperature, the plastic warps and the cap does not make a tight seal any more.
* Eagle here at found a great replacement bottle. It’s made by MOROSO (see moroso.com) I found it for $99.95 at www.summitracing.com part number MOR-63651.
I bought a 16lb closed system radiator cap locally and I also had to buy fittings for it.
It has an 1/8 opening for an overflow tank, but I just capped that off because the standard plastic tank doesn’t use one.
I’ve run the a/c and ran hard for several hours, and it’s stayed cool.
* I also found that when you fill the system with antifreeze, that you should point the front of the Jeep downhill (to get the engine block level). There’s a temperature sensor plug (use a 13mm long socket to remove it) at the back of the engine block by the last fuel injector. Remove the sensor and then fill the system using a funnel at the smaller opening on the thermostat housing until you see fluid coming out of the sensor hole. Put the sensor back in quickly.
* The system will automatically bleed off excess fluid for the first several times that you run it until the right balance is achieved.
* If you decide to just run with the plastic bottle again, fill it until the fluid reaches the post on the inside of the bottle.
* At toolking, you can purchase a STANT radiator pressure tool for about $80 that can check for pressure problems with the system. It can detect possible leaks in the head gasket or a possible cracked head or block. It can also tell you if there’s a combustion compression leak into the system.
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* I considered converting to an open system as some have recommended. However, I had just purchased a new radiator and found the MOROSO bottle to be a great alternative.
Good luck…

ps: Yes, if the bottle is cracked, you will overheat. At sea level water boils at 212degrees. For each lb of pressure that the cap puts on the system, the boiling point increases by about 3 degrees. Therefore, with a 15lb cap would increase the boiling point by 45degrees - at sea level, pure water would then boil at 257degrees. The antifreeze increases the boiling point even further. Cracked bottle = No pressure = lower boiling point.

gw204,

I also have a 88 XJ I recommend at minimum you repleace:

1) Mechanical fan clutch - get one that looks just like the AC Delco OEM cluch
2) Plastic pressure bottle - you can get it at the dealer - $50, quadratec.com - $20, or go with the Moroso tank for $80-$100.
3) Thermostat - go to the dealer and buy a 195F thermostat. My radiator shop told me one time at 225F can mess up a thermostat.

If you are into replacing the heater hoses you might as well do a complete cooling system service.

If you plan on replacing the heater hoses go buy them at the dealer, the goodyeard hoses just did not fit right and they did not have all 6 pieces listed.

If you are unsure of the radiator age then time to install a new one. I have a GDI 3 core on my 88 XJ but next time I may go with a Modine. In my mind both brands are good. If you change the radiator I have some tips for you on the transmission lines, just ask and I'll tell you. There a $100 deal on the GDI. It included delivery to your door, the guys on here can tell you where to get it.

radiator hoses - get a brand you trust. Make sure to transfer the antichaffe to the new hoses.

I use distilled water to to flush and fill the block. Buy the coolant brand you like. I found it took me 8 gallons of distilled to get down to less than 2% old coolant. I could get 2 gallons of coolant out through the pet cock each time.

The petcock for the radiator is located on the passenger side tank of the radiator. You will have to remove the grill to gain access. It points toward the passenger side fender. You will need 2 feet of 1/4 hose to drain the coolant into a bucket.

Here an article on filling the engine with coolant: http://www.olypen.com/craigh/cooling.htm

Here is an article on flushing the heater core, you might as well do this while you are changing heater hoses. http://www.olypen.com/craigh/heater.htm

You may fix your problem by doing the first 3 items but if you want to renew the cooling system then do all of it.

Martin

I've heard a lot about replacing the stock thermostat with a 180*-190* one.

The following articles have some interesting thoughts on how to keep our XJ's cool.

Check out this XJ's experience

Is your Jeep 4.0 engine getting hot under the collar?

Here is another good colling system mod!!

Renix Cooling -
DEFINITELY replace the thermostat! If you EVER overheat, replace it! I go so far as to keep a couple extras on hand so I don't have to go looking! I use the 180* version - it flows coolant a little sooner and helps a bit.

If you haven't replaced the fan clutch or suspect it is over 5 years old, replace it as well. A tip on aftermarket units - I've found that they are usually just a TOUCH longer than OEMR, so you will need to unbolt the top crossmember, which will allow you to lean the radiator forward and pick up that extra 1/4"-1/2" clearance you will need.

Check the thermal switch in the driver's side radiator tank. They go out over time, and need to be replaced. They are OEMR only, and I don't remember the cost but it seemed reasonable at the time ($20 or so, please advise when you get yours.) I find that putting som Teflon compound or RTV Copper doesn't go amiss when installing, either (don't use any RTV except Copper - the rest are non-conductive.)

Make sure you don't have any hoses leaking. You can find heater hoses with the right-angle bend at the local, but they are spendy. The hose assemblies don't happen (you know, the tee with the nice crimped joins?) you will have to cut the crimp sleeves off and reuse the tees. I am working on a replacement for that as well - will be Copper lines and vibration stubs for everything...

I also like to wire a toggle switch in parallel with the thermal fan switch and run it to the console somewhere in easy reach (my wife's auto has it right next to the shifter) so I can turn the fan on manually if I think I'll be sitting in traffic. The TFS doesn't kick on until about 215* and off at 198*, but I can turn the fan on manually as soon as I get in line somewhere (parking line, drive-thru, California Freeways, &c.)

Change any hoses over two years old. Check for glazing/wear on fan belt and pullys (glazing can be broken with Scotch-Brite rather handily.) Replace fan belt if over 50Kmiles. While you have the fan belt off, give the water pump and fan idler pullys a grab and check for excessive play or bearing noise. The fan idler is the compleat bracket (the one that supports the aircon compressor!) and goes for about $60-65, OEMR only. Remember there is a bolt at the very bottom when you go to replace it...

If you are changing your hoses (sounds like you should,) make sure to give your system a good flushing before you pull it apart. Contamination will collect in the hoses and come out with them.

Make sure your replacement lower (suction) hose has a "spring" inside - move the one over from the old hose if not. This keeps the hose from collapsing under suction, and killing off your coolant volume.

Make sure you "burp" the air out of the system - it will collect behind the thermostat. This is easily done by drilling two 1/16" holes in the flange of the thermostat itself, and installing it with the holes at 6 o'clock and 12 o'clock. The lower hole will pass water when the upper allows air to escape. I like to fill the system with the upper hose disconnected at the thermostat until I see coolant come thru. NOTE - failure to burp the system will result in an air pocket at the thermostat, and it WILL NOT OPEN. BIG problems!

Please feel free to ask if you have any questions.

5-90

The symptom of heating up when stopped and dropping to normal when moving indicates with 99% certainty that the viscous clutch on the mechanical (primary) fan is shot. Take Martin's advice on a replacement. Clearance is limited in there and many aftermarket units listed for the XJ actually won't fit because they're just a tab deeper than the OEM unit.

I also agree with 5-90 that you should replace the thermostat, however I disagree on the 180 rating. The engine was designed to operate with a 195-degree thermostst. With the overheating you experienced, that 15 degree difference would make no difference whatsoever. Once the thermostat is open, it doesn't matter what it has stamped on it -- if the system won't handle the heat with an open thermostst, you have other problems -- i.e. fan clutch, in your case.

Eagle is correct - there is minimal difference when the engine gets hot between thermostats (once it's open, it's not a thermostat issue anymore...)

However, since I spend so much time in traffic, I find that having the thermostat open that much sooner is a help. It's easier to prevent overheating in traffic when you have coolant flowing quicker - that and the manual fan override switch have saved me several times. It is an alteration to consider based upon the expected traffic in your area. If I lived in Flagstaff Metro (like we plan on doing...) there isn't enough traffic for the 180* to help and I'd go back to the 195*.

5-90

I have a 88XJ as well. and have had the same prob. could never figure it out. I took it to a shop and he said the motor had a air pocket in it . ( this is what he says anyway) kind of wierd. another new therostat and got the air pocket out. worked fine since. good luck...

also hesco has a nice high flow water pump