My XJ likes it hot, real HOT

Like this hot:firedevil:flame:, well almost.

I have a 1990 XJ, Renix 4.0, AX15, 192,000 miles. Starting last week, it pretty much decided it likes to boil the coolant out of the "pressure" bottle.

Less than 500 miles ago, I replaced the water pump because the bearing in it was defenitly shot. This past weekend I replaced the thermostat (195*), and the thermostat housing with a new '95 housing so I could burp the air out of the system a little. At the same time we flushed the radiator.

It still boils the coolant. Does anyone else's do/ done this? I am going to wire my e-fan to a switch so I can turn it on as a bandaid until I find out what the real issue it.

If I buy a new radiator, would it be worth it to get a new one for the Renix cooling system, or go ahead and convert over to the HO version? (I know one is open and the other closed, I just forget which right now)

Thanks.

First, go and get yourself a Stant 10244 pressure cap. It is off the Volvo 740 series with the 2.3 L engine. If will seal on the pressure bottle better than Aftermarket/OEM caps, has a lower profile so it won't impact the underside of hood when the bottle expands, and it has a higher pressure rating so it will raise the boiling point of the coolant.

Don't forget--when COLD the pressure bottle should be no more than 1/3 full--all that HOT and expanded coolant has to have somewhere to go.

Renix is closed--pressure bottle instead of recovery bottle, no cap on radiator.

Ok, all that said--you might have a headgasket issue.

The fact that it changed "suddenly" is concerning. I would have thought air in the system, but you say it was fine after the water pump replacement and before last week.

You can rent the system pressure tester from vatozone or anyplace that loans tools. Holding 16psi forever is a prerequisite to decent cooling performance. It's like a pressure cooker; the pressure raises the boiling point. No pressure == boilover. Even a pinhole in the pump or tstat housing gasket is bad. I wouldn't bother to do anything else before this test.

Joe; how much higher is the relief on that cap? Considering the pressure bottles, radiators, and cooling hoses are all known to blow, and the closed system is generally fragile, I'm not sure if I like the idea of a higher pressure cap. The system should work at the pressure that it was (poorly) designed for.

Converting to the open system is a good move IMO but again if it's not holding pressure, and the leak is in your engine somewhere, the conversion will not help it.

Hmm. Concerning. The other day, mine went up to around 260°. When I got home, I was a tard and forgot to let the engine cool down, so when I twisted the reservoir cap a little, coolant ran into the reservoir bottle and was boiling.

However, I have a cracked radiator and a tranny coolant line needing replaced, so I hope that's all it was. Plus, it was a little low on coolant (it took a whole jug of Peak).

Ok, all that said--you might have a headgasket issue

Click to expand...

Thats what my uncle who helped me with it said. As far as I can tell, there is no coolant in the oil. But he said there doesnt have to be, it could just be blowing the compression from the cylinders into the coolant system.

Right after I posted this, I went and did what I call a "rev test" haha. I just reved the engine a little to see if any pressure did build up.When I let off the throttle, the coolant started "boiling", but only for about 10 seconds, then stopped. It would boil out, and I dont think the engine even got hot enough to boil the coolant. This would mean a bad head gasket right? Also, the coolant bottle was less than 1/3rd full, then when I let off the throttle it would bubble out, then drain back into the system.



The current pressure bottle will not hold much pressure, and it is an aftermarket one because I cracked my old one about two years ago. The factory cap would not thread onto the new bottle, so I dont think the cap you mentioned would either.


Right now I am also considering buying a car to DD and not worry about having to finish a project on my jeep before work the next day....