I noticed that my high speed radiator fan is coming on much more often, typically at idle at a stoplight. The temperatures here in Virginia are chilly, so it is not an outside temp issue. (I had an earlier post about the voltage dipping to 12 when it comes on at idle RPM, but that was resolved.)

I realize that the temp gauge is more like an idiot light, but it does not budge off middle but I know (or think I know) that engine temp plays a role in the high speed fan.

Given that this is a new phenomena, I would like to get your view on probable causes (thermostat, radiator, water pump blades not circulating enough coolant at idle, or bad fan switch?)

The just turned 68k and it the fan has been coming on more frequently for the last month or so. I am getting ready to have some overdue (60k)maintenance performed (fuel filter, u-joint grease, brake fluid and coolant replace).

Given that the coolant must be drained anyway, I was thinking about the plastic thermostat tower, the thermostat, upper and lower hoses, and crossover pipe, and maybe even the water pump (+idler pulley and belt tensioner), even though it has low mileage.

Thoughts?

 

I recently went through that exact same problem. I had already replaced my idlers and belt previously. I ended up replacing both radiator hoses, water pump (was original plastic), T-stat and housing (both also original), ECU temp sensor, flushed and new coolant. The old coolant was an odd color like it had been mixed with something different along the way.
The water pump was actually the easiest thing to replace. The T-stat housing there is a bolt under the intake that with a crowfoot 8mm wrench took about 20 mins to get out. Then 20 mins to get back in. Then let it idle for 30 mins with reservoir cap off and added more coolant after the T-stat opened. Then took it for a drive and it needed about another pint and now its stable and no more high speed fans ever,


Dave

 

Thanks Dave! Hope you are doing well.


What/where is the ECU temp sensor? Did you replace your water pump with one that has metal impellers, or stay with the plastic? I have heard arguments both ways.

 

The temp sensor is on the crossover pipe that the short hose from the t-stat tower goes to. It was only $5 and a common part. You will see it as soon as you get the plastic engine covers off. I also replaced that short hose of course. I saw arguments both ways on the impeller also and ended up using a metal one that was highly rated. It was actually the easiest water pump I ever replaced. Guess the engineer that designs the built in pain-in-the-*** factors was out sick that day. But that easy part was more than cancelled out by the one bolt for the t-stat housing under the intake. At best you get a 1/4 turn at a time. But still better than removing the intake unless you plan on doing the octopus also.
I am doing ok and hope all is well with you too.



Dave

 

Dave,


Thanks again.


With your water pump, I take it that you only have to replace the gasket that comes with the unit and not the rubber O-rings as I have been reading? Do you remember the brand name of the pump? Sounds like a good one. And, lastly, do you remember the torque settings for the housing and water pump? I was going to hire this out because of the nut on the housing, but it sounds like it can be removed with the crows foot, which I already have.

 

It was the KM Premium Quality one. I forget the torque but I will see if I still have my cheat sheet I made with all the torque values.
No O rings just a metal gasket. Be careful as mine slipped as I was maneuvering the pump into the hole and I bent it slightly and had to straighten it out. I ended up putting 2 bolts through the water pump holes and hanging the gasket off them while lining the pump up and that worked fine.


Dave

 

It's possible that you thermostat is not opening all the way. I would proceed with all the parts you mentioned.
It would also be wise to do the Realgauge mod that Steve offers on his jagwrangler site, or at least the Ultragauge or elm327/torque combination for real time monitoring.
The potential cost of an overheat is too high to ignore.

 

Thermostat Housing bolts: 8-10 Nm.

A crow's foot will reach the awkward bolts on the Housing. Several members have used hex bolts instead of the standard ones when replacing the housing.

Water Pump:


(click on the image to enlarge it)

Graham

 

Those bolts are 8mm and no crows foot set short of a very high end one is going to include that size. I caught a Matco truck and he couldn't even find one in his catalogs.

If you find one reasonably priced or even in a reasonably priced set please post the info.

The common solution is to bend a cheap 8mm box end wrench to get it loose. I also ground down a cheap 8mm socket to fit. Think I have given both away over the years to other members needing this solution. On one car I replaced the original bolts with socket head bolts and washers and on the other cut a slot with a Dremel tool for a blade screwdriver. If you are buying bolts get the rear ones an eighth inch shorter than the originals in order to clear the intake manifold. If reusing the bolts swap the two rear bolts with the slightly shorter thermostat housing cover bolts.

Oh, be sure to paint the aluminum tower and thermostat cover black to match the engine. The bright aluminum looks really out of place on the otherwise all black engine and will then proceeds to corrode to an even uglier finish.

 

The 8mm I used I borrowed from a local shop (That won't work on Jags or my SAAB for that matter). It had a hinged socket at the bend and that made it a little easier but not much.



Dave

 

This is how I did my thermostat housing and water pump

Link http://jagrepair.com/ThermostatHousing4XK8.htm

Link http://jagrepair.com/WaterPumpCrossoverPipexk8.htm

 

Error

 

Thank all of you for your replies. Parts are on order! I hope I have the same result as Dave. Even of not, this work has been overdue.

 

I'm sure it will fix it. The actual problem is likely the t-stat but replacing all the stuff at once makes sense just in case it isn't and gives the piece of mind that the cooling system should be good to go for a long while. Unless the octopus starts leaking. If the problem was something more nasty like a head gasket you'd probably have more severe symptoms. And remember you can use the Dayco idlers that are metal and not expensive.
About the temp gauge: Mine of course stayed near the middle also when the fans went into hyper drive. Assuming the ECU temp sensor is working correctly the fans don't go into high speed until about 217ish. Thats how useless the gauge is.


Dave

 

Just ordered an 8mm crows foot from an industrial supplier ($35 including shipping). They are hard to find!

Is there any gasket sealant or anything you used on the housing, pump, etc.?

Thanks!

Steve

 

The water pump, thermostat cover and thermostat housing all have rubberized seals that should come with the parts. At least mine did. No additional sealant is necessary.

 

Just unbolt the inlet manifold and pull it up at the front. It will pivot on the two bolts by the throttle housing. You can then get straight on the bolt with a normal 1/4 drive socket. Thats how we used to do them.

 

I used no sealants, just made sure everything was as clean as I could get it. Unless you are going to also replace the crossover pipe be very careful with the short hose and clamps etc as its really thin brittle plastic and some people have had them crack and leak,


Dave

 

Just be sure that all the surface is clean and you should replace the short hose between the tower and the crossover pipe.

 

Thanks Dave. I have ordered the crossover pipe as well and plan to replace it with everything else.