Upgraded cooling system still overheating?

I have an '87 XJ Wagoneer with the 4.0, NP242, AW4, 30" tires and 3.55 gears for starters. I have updated the cooling system to the newer open cooling system. During that update I installed a newer style heater control valve, radiator filler neck, all-aluminum radiator, 16lb radiator cap, overflow tank with window, and new hoses. I have also installed a FFDyanmics 3-fan cooling system, new water pump, 195* t-stat, and installed some vents in my hood. I installed a new fel-pro severe duty headgasket a few months back, but the problem has been prior to that. I had the cylinder head magnafluxed and machined, and it came out good.

The problem that I'm having is that when I drive in stop and go traffic, or slow offroad conditions, the system seems to build up enough pressure that it will fill up my overflow tank and spew all of my coolant out the breather hole at the top of my overflow tank. Then it ends up leaking all of my coolant out to where it overheats. The system will run steady at the line below the center line on the gauge until it leaks enough coolant out to overheat. So it seems its not overheating then building up pressure.

I can drive on the hwy all day long and it never has a problem. I can even drive over the Cascade Mtn range and have no problems. My first thought was that the fans aren't working, or cooling enough. Well they are definitely turning on and cool the engine down as soon as they turn on. It seems that the cooling system building up internal pressure is the problem.

Do you guys have any suggestions? I mean thats the main reason I installed the new head gasket but it didn't really change anything.

I have the tripple threat system and this summer I drove around in 105 degree weather with only two of my fans hooked up. It never got over 210. I don't think it is the fans. I would bet money on the head. I just helped my friend do a head gasket on his honda and it still overheated so we swapped on a junkyard head and its fine now. He got both heads magnafluxed and decked. I don't think magnafluxing works all that well.

Did you ever check for exhaust gasses in your coolant?

No, is there a tool/gadget that can check that?

check with your garage there is a dye they put in cooling sys to check for cyl head leak

I would also second the head issue. When you blew your head gasket did you overheat your motor?

Radiator cap?

I was told that the head gasket was probably blown so I changed it out, when I inspected the old one, it seemed perfect. The hottest the motor ever got was the line after the middle line on the gauge. The radiator cap? Its a brand new Stant iirc.

Have you gotten all the air out?

souske said:

Have you gotten all the air out?

Click to expand...

x2 on that

Yeah, I burp the system every time I add coolant. I added a newer t-stat housing with the sensor, which I use as a burping method. And I also have the coolant back flush tee in there that I burp from as well, so I know that it gets burped good. I even squeeze the lower radiator hose to pump all the air bubble out when everything is open. I've got it down to a science now. lol

I'm with the others--go to the parts store and rent the coolant tester, you have to purchase the chemical, and test the system for combustion gases.

When you replaced the headgasket did you clean out the holes/threads in the block? Did you use new headbolts? How much has been surfaced off the head? Did you use thread sealer on bolt # 11 and torque it to the lower spec?

Try a different radiator cap. Its unlikely that this is the fix. But if it where, it would be the simplest and cheapest. Just because you have a new radiator cap doesn't mean you didn't get a bad one. I am king of getting faulty parts. I blew two napa cv axles within 50 miles. Manufacturing defect.

nrpalmer32 said:

Yeah, I burp the system every time I add coolant. I added a newer t-stat housing with the sensor, which I use as a burping method. And I also have the coolant back flush tee in there that I burp from as well, so I know that it gets burped good. I even squeeze the lower radiator hose to pump all the air bubble out when everything is open. I've got it down to a science now. lol

Click to expand...

Could you P.M me with your "burping" method. I'm having issues with my coolig system as well. I have a thermo. housing w/ sensor. I'm guessing you loosen that up to bleed air out. What are you talking about a back-flush tee?
Thanks for your post. I'm keeping up w/ it to see what finally resolves your issue.
Thanks,
AL

try parking nosed downhill, then bleed from the coolant sensor on the back of the head

Thanks for the replies guys! This is my second new radiator cap so I'm guessing this isn't it.

When I did the head gasket, I had to take 14 thousands machined off the head to make it flat.

I didn't use new head bolts because these all looked brand new, plus none of them had any paint on the bolt heads.

I did use loctite thread sealer on bolt number 11, and torqued them down to specs.

I cleaned the head bolt holes with compressed air, as well as changed all the coolant out and oil after reinstalling the head.

My thought now is that maybe the t-stat is sticking? Recently the temp is even overheating during hwy speeds, and it seemed to get hotter/colder randomly.

Oh and before you asked, I did retorque the bolts. lol Also I have a Stant SuperStat t-stat. If this is the prob, I'm going to get a Robert Shaw but what do you guys think?

Is the t stat stock of high flow? I was running a high flow and it was causing to much flow and would saturate the radiator with heat. Replaced it with a stock one and that helped a lot. I discovered the high flow ones where hitting the head when open and caused it to never fully close.

Also try a bottle of watter wetter, it dropped my temps by almost 20F.

But it sounds like a issue with the radiator neck or cap of it is leaking like that.

The radiator is the original renix style but I added the newer upper radiator hose and inserted a radiator filler tee into the upper hose.

The t-stat is a stock style t-stat, but I was thinking of getting a Robert Shaw or Stewart/Shaw (a modified Robert Shaw t-stat). So you're saying that the modified one might be a bad idea for the XJ?
Here is a pic BUT I don't use that radiator cap anymore, I use the Super-Stant cap that has a vent lever on it.

Here you go, here's a pic with it:

I found that the supplied fan controller with the triple threat fan kit is not adequate for the 3 fans and will get hot and not provide enough current to the fans. I used the controller to trigger a 75 amp relay to power the fans and it made a noticable difference.

They actually hooked me up with two fan controllers for the triple fan kit, and it seems to blow a heck of a lot of air through. It enough that it'll suck a peice of paper to the grill of the XJ. lol

Get ahold of a infarared thermometer and inspect temps around the block. Maybe a coolant jacket is partially clogged..... Pull that thermomstat and boiling water test it. Make sure you get one with a bleeder screw.