[VillageIdiot]

I am having some cooling system trouble with my 1994 Dodge Spirit 4 cylinder. I changed the thermostat and gasket recently and I was told to bleed any trapped air out of the system by pointing the nose of the car slightly uphill and running the engine with the radiator cap off until the cooling fan kicks in. If I run the car with the rad cap off, the coolant in the radiator will start boiling before the radiator fan turns on. That's not right, is it? If I put the radiator cap on then let the engine run until the cooling fan turns on, I can feel water boiling in the upper radiator hose and at the radiator cap. Any idea what is causing that? The car doesn't overheat while driving normally and the coolant doesn't look dirty.

Second problem. It seems that my cooling system doesn't make or hold any pressure. I can drive the car for a length of time, shut if off and right away open the radiator cap (which at this point is only lukewarm to the touch) and there's no obvious pressure release. I have tried 2 different used radiator caps and 1 new one all with the same lack of pressurization. I don't notice any oil in the coolant, or coolant in the oil or any crusty white buildup on the spark plugs, so I don't think the headgasket is bad, is it? Any ideas what's causing this to happen?

 

[valiant67]

You need to buy, borrow or rent a cooling system pressure tester. Air is getting into the system somewhere, that's why you hear the bubbling/boiling noise, why there is no pressure and likely why the car seems to get hot before the fan kicks on. The air could be from a head gasket leak, a weak hose clamp, a hairline crack in a radiator tank, any number of places. Sometimes you won't notice coolant leaking from the place air is entering because it evaporates before it hits the ground. The tester will even let you verify the new radiator cap is really good.

 

[chuzz]

I had that happen with the 94 Spirit I had and finally discovered one of my hose clamps was a little bit loose. When I pressure tested the system, a couple of drops of coolant showed up on the lower radiator hose. I tightened all clamps, including the heater hoses and it worked like a charm. Perhaps this will work for you.

 

[VillageIdiot]

So, I made a video of my cooling system problem. The only time the bubbles pop is right before the cooling fan comes on. Any other time and there are no bubbles. I drilled a hole in the thermostat already. Check the video (bubble action at the 1:05 mark)

http://www.youtube.com/watch?v=4eF-yR5NugI&list=UU6vubBTju44HYDDTTrWfrjg&index=1&feature=plcp

 

[John Wood]

It is possibly a tiny leak in the headgasket, but call your local AutoZone store to see if they have a coolant system pressure tester you can borrow on their loan-a-tool program. That would be the best way to test the cooling system integrity. The other option is to add a product to your coolant reservoir that detects unburned hydrocarbons or exhaust byproducts. There are test kits available at most auto parts stores but they are a bit pricey in my opinion.

I have seen headgasket leaks act just like that. You get no bubbles when it is cool, but just before the fan kicks on, you get a constant stream of tiny bubbles that never seems to end. It is the metal expansion between the steel block and aluminum head combined with a tiny crack in the headgasket fire ring that ultimately causes the leak. With no cross contamination between oil & coolant, you will probably be OK for a little while, but the problem will only get worse.

 

[Bob Lincoln]

Any chance you put the thermostat in backwards? The spring side faces the cylinder head.

I agree, bubbles like that can mean the head gasket is about to go.

Why was the thermostat replaced? Were there any issues that prompted it? Has it ever overheated before?

My thermostat stuck shut, and I shut it down quickly, but two days later the temperature started drifting up to the halfway mark while driving, idle was rough, and bubbles in the coolant at the radiator neck. Then steam started coming out the tailpipe. The head gasket ruptured between cyl 1 and a coolant passage.

 

[VillageIdiot]

When I bought it and was bringing it home it was running a bit on the hot side but I was still getting heat through the heater. The old thermostat wasnt quite sticking, but was opening very slowly so I replaced it. The guy I bought it from said it would run hot on the highway, I assume because of the bad thermostat. The radiator was replaced (before I bought it) with a used one.

 

[Bob Lincoln]

A thermostat that's slow to open will run the system cool, not hot.

Running hot can be a number of things, including a thermostat that's sticking shut, cooling fan not coming on when it should, radiator clogged, improper mix of antifreeze and water, bad pressure cap, low coolant level, failing water pump, slipping drive belt...

Could be that the head gasket was already failing when you bought it. It's not a hard job. I did it for the first time last spring, and changed the timing belt, which has to come off, anyway.

 

[VillageIdiot]

Well, whichever way the old thermostat was sticking, it was making the car run hot. I put a new one in and it runs normal temperature while driving. The radiator cap is new, from Carquest .I assume the cooling fan comes on when it should..but is there a reason why it be late turning on?

How long did it take you to do your headgasket? I've just got basic tools, semi competent skills and a Haynes manual.

 

[Bob Lincoln]

I work outside with no garage, and it was winter, so I didn't tackle it for weeks. However, I estimate that because I also replaced the timing belt, water pump and drive belts, and poured combustion chamber cleaner in the cylinders and let it set, it was 16 hours on the clock. But normally just changing the head gasket and timing belt with no special cleaning (I scrubbed the head and manifolds), it was probably about an 8 hr job without the frills. I also had trouble with the bolts from exhaust manifold to down pipe, and accidentally left the old gasket in and added a new one, so I lost several hours struggling there, before I figured out why the bolts wouldn't reach and seal it. It's actually a very easy job. You MUST use a torque wrench on the head bolts and tighten in the proper sequence. And use new bolts, no matter what anyone says. They are torque-to-yield, so they are not to be re-used.

 

[John Wood]

You'll need a torque wrench for sure. I often see Harbor Freight coupons for a $9.99 1/2" drive, click over style. That would probably be good enough for what your doing. Mail order a Mopar Performance HG and use any of the name brand replacement head bolts. You'll also need valve cover gaskets. If you are taking off the timing belt (instead of suspending it), just replace it. Some of these items can be ordered cheaply on-line (Rock Auto, E-Bay,etc.). Replace the Camshaft seal since it is a piece of cake to do with the head off. You will also need replacement exhaust manifold to converter pipe bolts.

Contrary to most recommendations, you can do a slip and slide method. The instructions are still around somewhere. I did it twice on 2 old cars that would have been junked and never had a leak. The owners would not pay the quoted price of about $500 for a full R&R and couldn't do it themselves. I followed the status of these cars for about 3 years and they never had a problem. The method seems to work good for tiny leaks like you have (i.e. head not likely deformed). There is never a guarantee with that shortcut, but it really cuts out a lot of labor.

 

[B10alia]

It helps to have a friend around when you do a head gasket ; the cylinder head is heavy and awkward to handle if you're alone. Also, a hint for reassembly if you have to do the head gasket: The sheet metal valve curtain needs to be squeezed slightly when you reinsert it. It has some spring to it and will catch on the head unless you squeeze it. The valve cover will not go back on properly if the curtain is not positioned properly. Seems simple, but it took me about an hour and half of frustration to figure this out.