2001 Malibu Overheating and Hard Start

[kitkat6936]

I have a 2001 Malibu with 119K miles that is both overheating quickly and is hard to start once it gets hot. Replaced thermostat. Replaced water pump. Replaced coolant temp sensor. Took thermostat back out - still overheating but it is taking a little longer to happen. Fans are coming on and work. Radiator is not plugged. There is no oil in the coolant nor is there any coolant in the oil. There is no white smoke coming out of the tailpipe. There is no moisture coming out of the tailpipe. Was pulling a 420 code (catalytic converter) but just recently replaced the cat and there are no more codes (problem probably hasn't ruined new cat yet). Once the car starts it seems to run great -- until it overheats. There are no visible antifreeze leaks from either the intake manifold gasket or the head gasket. I am not losing antifreeze until the car gets hot and it pours out of the overflow. Whew.. I think I've covered everything. It has been suggested by several backyard mechanics that my head gasket is blown or that my heads are warped. I get a little nauseous when I think about the expense of this repair so any suggestions of what else could be wrong or could it be a combo of problems??

[ChevMali99]

I'm having the same problem with my 99. The car overheats really quick and it spews dex-cool out through the overflow. Now, I noticed that as soon as the I shut the engine off the remaining coolant in the reservoir shoots back into the radiator. I tend to believe there's a blockage of coolant somewhere that's not allowing the flow of it through out the engine. Also, I get no heat into the driver's cabin. I've read that it could be the thermostat stuck in a closed position, or that ultimately this could all be a dexcool symptom. The radiator is also making a clonking sound similar to that of home heating radiators.

At any rate, I'm prepared to replace the coolant reservoir, maybe replace the radiator (if needed), the water pump and the thermostat... But what should I tackle first? What is more than likely the cause for this?

[brcidd]

In both cases, when engine is hot- does radiator feel hot from top all the way to the bottom? I've seen radiators that are cold except for top two rows, you have got to be able to feel each row (tube) to determine if coolant is passing through all of them. In my case, two rows was not enough to keep up with the cooling demand- too much of a restriction...and the engine would overheat- replaced the radiator and all was well....mine was always throwing coolant out the overflow- basically boiling over after it warmed up.

[ChevMali99]

Originally Posted by brcidd

In both cases, when engine is hot- does radiator feel hot from top all the way to the bottom? I've seen radiators that are cold except for top two rows, you have got to be able to feel each row (tube) to determine if coolant is passing through all of them. In my case, two rows was not enough to keep up with the cooling demand- too much of a restriction...and the engine would overheat- replaced the radiator and all was well....mine was always throwing coolant out the overflow- basically boiling over after it warmed up.

Hey thanks for the reply... The hoses are piping hot. The one on the right (facing the car) that goes from the radiator to the engine, the one that goes from the reservoir to the radiator... It seems though that the coolant flows right back to the reservoir... Your experience lead me to believe the radiator might be clogged on its bottom half, is that even plausible?

[kitkat6936]

I have had my radiator checked (no blockages), replaced thermostat (twice), replaced coolant temp sensor, replaced water pump -- and still same problem. Car also doesn't want to start when the least bit hot. When cold it may start right away or give me a problem. Taking car in this week for detailed diagnostic but it looks like it might be a head gasket problem. I have not used dex-cool in the vehicle for over a year once I heard about all the problems associated with it. Good luck to you in remedying your problem - mine has been a great big headache!!

[ChevMali99]

Originally Posted by kitkat6936

I have had my radiator checked (no blockages), replaced thermostat (twice), replaced coolant temp sensor, replaced water pump -- and still same problem. Car also doesn't want to start when the least bit hot. When cold it may start right away or give me a problem. Taking car in this week for detailed diagnostic but it looks like it might be a head gasket problem. I have not used dex-cool in the vehicle for over a year once I heard about all the problems associated with it. Good luck to you in remedying your problem - mine has been a great big headache!!

Thanks for the reply. You still have the same problems?! Please post your findings.

[zappytiger]

Regarding your hard start problem when engine is hot, replace the fuel presure regulator. It worked for my 98 Malibu.

[manicmechanix]

Originally Posted by ChevMali99

Hey thanks for the reply... The hoses are piping hot. The one on the right (facing the car) that goes from the radiator to the engine, the one that goes from the reservoir to the radiator... It seems though that the coolant flows right back to the reservoir... Your experience lead me to believe the radiator might be clogged on its bottom half, is that even plausible?

Yes that's where the radiator clogs up first at the bottom. You might want to check your reservoir pressure cap on the outside chance that it isn't holding pressure. Then you want to completely fill the system with coolant and bleed the air out of it. If the upper radiator hose opens and it still overheats, you most likely have a clogged up radiator. Dex-cool will clogging up if air is in the cooling system. You might be able to get it flushed out without replacing the radiator. Maybe not, but the system would need flushed out anyway if you do need to replace the radiator.

The leaky intake manifolds on the 95-03 V6 probably can leak enough to lose pressure and suck air in as the engine cools.