Overheating and blown radiator tanks.

So, over a year ago I blew the stock side tank off my radiator. It had been overheating but not seriously so. I guess I should say I didn't blow the tank but it started leaking.

So I bought a new champion all aluminum radiator which helped the cooling but after almost a year it started leaking from both tanks. A few weeks ago I put a stocker back in and today it got a little warm and when I pulled in my driveway it completely blew the side tank out. I'm talking a split, not at the seams but it looks like you over inflated the thing and it had a blow out.

My Jeep is an 01 with an 0331 head but...I have seen no visual signs of cracking. No water in the oil, no condensate on the oil cap.

I'm wondering possible head gasket? At idle I am not seeing any bubbles in the coolant nor am I seeing any discoloration or smoke out the tailpipe.

Ideas? Is there a way to REALLY check for head or head gasket issues without physically removing the head?

You can buy an adapter to fit in the spark plug hole with an air nipple, I made my own from and old tire valve, an old spark plug and some silver solder. Run each cylinder up to TDC (firing order) and pump some air in there with the radiator cap off. The air pressure will usually try to turn the engine over, you can try to lock it down with a socket T bar and the harmonic balance bolt. Or do what I do and take the inspection cover off of the bell housing and jam a couple of wedges of wood into the starter ring gears.

A bad head gasket and the air will eventually bubble out the filler neck or up into the surge tank on the Renix models. A tiny leak may be hard to spot, tiny bubbles, be even they become evident eventually.

Regulate the air down to around 15 PSI (or even a little lower) or you can even use a bicycle tire foot pump.

I tried a litmus type tester, for exhaust gas in the coolant, with mixed results. They say the test kits have gotten better.

Something to think about and I haven't heard it talked about much. but much of the weight is in the ends of the radiator. The under side support kind of leaves all that weight hanging in the air. The whole radiator is basically supported by two one inch rubber doughnuts maybe a quarter or possibly a third of the way from the end tanks. Pounding the XJ on rocks or potholes has got to stress the end tanks, simple leverage. Dodges used to pop the top radiator mounts for much the same reason. Some extra support on the bottom of the radiator, near the end tanks may help or like you said it may be a totally different issue and the pressure is what is causing the elaks and cracks. I've seen multiple XJ radiators pop leaks in the same spot, different manufactures and different styles, all metal, metal with plastic tanks, aluminum and copper, all spring leaks in the same spot upper right side of the radiator (usually the inside behind the shroud) where the cross passages meet the tank base. Even the same spot in different XJ's, so it seems likely it may be a design flaw and that particular spot gets stressed (or both hotter and stressed) than the rest of the radiator.

I've actually seen the bottom flat sheet metal piece the bottom mounting rods are welded to, bow significantly. If the bottom support cross brace bows, it almost has to stress the ends.

The Dodge solution was a piece of hard foam (all weather) that supported the whole underside of the radiator instead of relying on a few fixed mounting points as support.

Just thinking out loud.

I'd sure enough look at my radiator or surge tank cap, I've seen guys test a radiator for leaks using compressed air and blow a hole in the radiator with 25-30 PSI. Mine seems perfectly happy with a 14 PSI cap, instead of the 16 PSI cap.

Those drops of condensation that come out of your exhaust pipe in the early morning may show up as a tint on a white paper towel if you have a compression/exhaust leak into the cooling system. Some coolant is going to find it's way into the cylinders, it isn't a one way thing. It may turn to steam when the cylinder fires, but when it condenses again at the exhaust tip it may show a very light tint the same color as your coolant, red, green blue whatever it is.

I'm 99% sure this is a pressure problem. Today it was hot. There is about a five mile 5-6% grade to pull to get to my house. I had my trailer on and I noticed the temp get a little warmer and warmer as we got home. Pulled into the driveway and shut it off (giving it a min or two to cool down) about 15 sec after I shut it off the tank blew out. I'm not talking started leaking around the tubes. I'm talking a 2 inch by ten inch gash in the outward wall of the tank.

Got me, never seen it before. I have seen a tranny get so hot the heat exchanger in the left side of the radiator actually melted a plastic end cap. My guess was the heat exchanger was actually touching the inside of the plastic end cap, likely a manufacturing flaw.

My thinking is the only thing that could build that much pressure that fast is steam. And the steam should vent out the radiator cap into the recovery tank. Unless it builds so fast the small rubber tube to the recovery tank couldn't handle the surge. In all likelihood it would blow the line right off the nipple at the filler cap. Seems odd the seams of the end tanks didn't separate or something else split, before the end tank itself blew.

If I remember correctly the boiling point of a 50/50 coolant mix, at 16 PSI is around 265 F.

If your radiator pressure cap isn't stuck shut, I would definitely think about adding a timer so your aux fan stays on after engine shutdown for a minute or so, to help with convection cooling.

Another possible cause is maybe the thermostat is screwing up, stalls the coolant in the head until it cooks off and builds enough pressure to blow past the thermostat. It should show up as a temperature spikes at the cluster gauge.

Or maybe your first guess is right and you have a tiny head gasket leak that eventually builds enough exhaust gas in the head and block to restrict the coolant flow, especially convection cooling after the motor is stopped.

This isn't specifically a Jeep answer.

I have had overheating/pressure problems with my other car, Nissan 1.8L.
I changed the thermostat, no change. I changed the coolant sensor, no change. I changed the water pump, no change. Tested the e-fans, no change. It ran fine, smooth, and cool MOST of the time. Then out of nowhere the gauge needle would start rising into the red.

All this stuff needed maintainence anyway, so I did not consider that I was just throwing parts at it. There was no coolant in the oil, no oil in the coolant.

I swore bitterly.

Took it to the shop. They did a leak down test, they did an exhaust gas test...nothing, nothing measurable at least. OK, here's the meat:>

They did kind of a reverse pressure test on the radiator...pressure in the radiator went to MAX after only 3 minutes of idling. It's getting a new head gasket right now at ~~$1200 (I don't do engine work on ricers). When they took it off they found a tiny failure in the gasket between one of the cylinders and one of the water galleries, pressurizing the system. It avoided the oil galleries altogether... Just sayin'.

If I were you, I'd first get rid of the stock plastic ended radiator and buy an all metal radiator with a 16 lb. (no lever) cap. If you have pressure problems after that, you probably have a similar problem

If you read my first post I said I had an all aluminum champion radiator in there. It failed too.

I've had decent results with the block tester chemical you mix coolant into looking for a reaction. I've heard people mention being able to see the cracks in the 0331 head through the oil fill hole in the valve cover as well but I've never personally witnessed that one. Valve cover gaskets are cheap and easy to replace might be worth it to pop it off and take a look :dunno: from what I have read on here though when the 0331 goes it usually sends oil into the coolant.

Good luck.

The hole

Damn.

I had a customers early Durango with a 5.2 liter that blew out the side tanks like that 2 times...First it was an upper hose, replaced spring clamp with worm clamp.and turned it loose,couple weeks went by..... it was a body shop repair after an accident..... the replacement factory radiator after the accident blew out about month later, then the 2nd factory radiator did the same thing a week later......., it turned out to be a head gasket....... It never turned up in the cooling system combustion test, I pulled all the spark plugs, put my cooling system pressure checker on it and pumped it up to the max and let it sit, would repump a couple times during the day, took a long time, but had coolant in one of the cylinders...... you would think the pressure would overcome the radiator cap........

Correction: Durango has top and bottom tanks or crossflow? either way it split the tanks...... god my memory is bad....

I didn't read all the posts, but how do the plugs look?

Haven't pulled them yet. Waiting for my new radiator to get here.

It's kind of hard to pressure test a coolant system with a fist sized hole on the radiator

Would a build up of gunkish restrictive stuff in the coolant channels cause for a higher pressure? Sort of like plaque in arteries causing a high blood pressure? When I got my '89, a couple of years ago, I was astonished as to all the gunk/trash/scale etc., that I flushed out, thusly relieving fluid flow.

Has your fan clutch ever been replaced? You better get that thing running so you can keep the supply of cool pics coming.

It might but that isn't my problem. My system has been flushed, cleaned, flushed some more and on top of that I've put new radiators in.

Speaking of that. Ordered a new CSF from DPG today. Soon as it gets here I guess I'll get to the bottom of where my pressure problems are coming from.

8Mud said:

If your radiator pressure cap isn't stuck shut.....

Click to expand...

^^this is by far the most likely culprit-- 16ish PSI shouldn't be anywhere close to blowing fist-sized holes in radiators. The failure after shutting it off also points to a pressure relief cap not working (pressure builds with temp. increase and temp. peaks soon after shut-down due to lack of coolant flow)

If nothing else, I'd make sure the new radiator gets a new pressure cap just in case.

All three radiators that failed have had new caps.

What about a clogged overflow line from the radiator to overflow bottle? That would keep the radiator cap from venting pressure.

This last time I noticed when I pulled the radiator put that the overflow bottle was full to the brim. That tells me that the cap was releasing pressure. I think it pushed all the coolant in there right before it blew. Maybe it flash steamed and the little coolant line couldn't keep up. I'm really not sure right now.