My 2002 Grand Caravan Sport 3.3L is acting very weird and I can't figure out why. First problem is a radiator leak. One week ago my wife complained that the heat wasn't working so I went out to check into it and found almost no coolant in the system. It took almost 2 gallons to fill it back up and as soon as I filled it up, I could see it dribbling out the bottom of the radiator. So I definitely have a radiator leak and new one comes in Monday. HOWEVER, when I filled up the fluid with the engine bone cold and started the motor, it ran very poorly. I figured it was no big deal so I proceeded to drive about 10 miles but during the trip the motor had NO power and the rpms were erratic. During this time there was NO check engine light. I returned home and shut the van off and went out the next day to look into it but when I started it up the following day, it ran perfectly. It ran strong for a whole week until today when the heat wasn't working again. So again I added another 2 gallons of coolant into the system, started the van, and the problem that happened last week reappeared. Engine running erratically with no power. So I shut it back off, let it sit for a few hours, turned it back on and the problem is gone. When the motor was off about a pint of coolant leaked out the radiator.

So.... How can filling up the coolant cause the motor to act like this? It seems like nonsense but so far the problem has happened twice. It seems like when the coolant dribbles out the radiator a little bit it is allowing the motor to run normally again which is scary because when the new radiator arrives Monday, I'm going to fill it up with coolant just as before but the coolant won't leak out.

I know this is all a bit odd. Unless I have a head gasket leak or frozen water pump there should be NO correlation between the coolant level and engine performance right??????? Any ideas?

 

Here's one possibility I can think of which could explain what you're seeing. With almost no coolant in the system, there is a good chance the engine overheated and blew the HG. If that did happen, at the point the coolant system is filled, lots of fluid is available to be pulled into the cylinders and cause misfire. Then when the fluid exits the system, there's much less available to affect combustion, and the engine runs better. Try filling the system; keep the cap off; start and run until the t-stat opens (topping off as necessary); and watch for bubbles in the radiator neck.

 

Now this makes sense! However, the temp gage on the cluster never rose above half so if it overheated then either the temp sensor is broke or the heat never reached the sensor. Is this possible? Also, If coolant was leaking into a cylinder wouldn't I see white smoke out the tail pipe?

 

The gauge is controlled by measuring the coolant temp, so if coolant is exiting quickly, and there is also air in the system, it would certainly seem possible that the gauge isn't measuring the actual engine temp. And the white would show up if coolant is being burned, but if it is snuffing out the combustion then there would be nothing but unburned fluid coming out the pipe. This is all just speculation on my part, trying to match what you're seeing to an actual physical problem. It will take some testing in order to find out if this theory is correct, or if it's something else that's causing this odd behavior.

 

Makes perfect sense to me! Question is do I want to dump the money into the van or buy another vehicle??? Thanks for all your help!

 

Once again, don't assume what I wrote above is correct - I wouldn't if it were mine. At least do the bubble test I described earlier. If the HG is really blown that badly, you should see bubbles in the coolant. AFA the decision to keep it, for me the main factor would be rust. If the van has lived in the rust belt, it's highly likely the underside is badly rusted, which often results in expensive structural problems and makes normally routine repairs much more difficult. But if there's little or no rust on your van, I would consider making the repairs. But I say that from the perspective of being able to DIY. If you're paying shop rates for repairs it's a more difficult decision to keep it.