98 Malibu Over-Heating

Some overheat problems I've had with mid-sized GMs of that era:

1) External, dirty radiator, passages between the fins entirely clogged up. Removed radiator, used heavy duty grease remover to and hose to clean out fins. Worked fine after that.

2) failed thermostat

3) The 3800 engine intake manifold gasket will leak cooling fluid directly into the cylinders. This should be obvious from lack of coolant in the radiator the the absence of spilled coolant on the engine or ground, because it's going out the tail pipe.

DON'T check the coolant level (radiator) if the engine is hot !!

Failed water pump?

Before it started overheating what happend ie was it running ok then siddenly it started overheating, did it loose power then overheating etc

possible causes water pump impellor has come loose

drive belt to water pump broken

water pump seized

radiator blocked by plastic bags stuck to front.

thermostat stuck shut.

loss of water

head gasket

over weak mixture.

when the car overheats carefully check the top and bottom hose are they both hot ?

is the top of the radiator as hot as the bottom

please report back

thnx

http://cr4.globalspec.com/search/sitesearch?do=show&sort=textmatchrank&srch=malibu&order=asc

i seem to remember hearing about impellers coming loose on water pump shafts during this era...

If you are losing anti freeze and cannot locate the cause as previously stated, they have had some problems with the EGR passage burning a hole in the intake plenum which is not metal and allowing the antifreeze to leak into the engine. If this is the case, don't drive it since if it gets really bad you can develope a hydraulic lock in a cylinder.

h

Are the passages within the radiator clear?

Had this problem with mine. After flushing out the radiator (reverse flow direction), the problem was solved.

Quite a bit of sludge came out that was not visible through the radiator cap opening.

Let us know what you find - Good luck!

Mallllliii BBBOOOOO! Thermostat maybe? Or you could be losing coolant somewhere?

As is typical with all gm's. The following are area's to review.

1. When engine running, are the hoses hard to squeeze.

if not, replace.

2. If you think that the head gaskets are Kaput, pull a couple of the spark plugs. If they are fouled or there is a heavy coolant odor, there is your answer.

3. You did not mention current mileage on the Booo. if above 120k, very possible the wawa pump is gone as most people don't change coolant at the rate of a 36 month interval with new.

Final recomendations: Complete a full backflushing of entire system. Please remove existing thermostat and chuck before the backflush re-install thermo housing, use a good internal cleaner after flush. run car for 15 to 20 mi around the block. Flush again, add fresh collant(full strength) Replace water pump, hoses. and drive the car.

I HEARD YOU CAN LOOSEN SOMETHING ,LIKE THE OIL CAP? AND IT TAKES SOME OF THE PRESSURE OFF OF IT.UNTIL YOU CAN GET IT HOME. ANYONE KNOW WHICH CAP OR HOSE IS BEST FOR THAT?

Radiator cap will release pressure if you have minor head gasket-type leak; this has gotten me home a few times during several decades of driving. If the pressurization is at the reservoir (that is, pressure cap on it) then that's the one to loosen. Normally, the cap you want goes directly onto the radiator, and usually has a pressure printed right on it, like, say, 8 psi, or may be in Bar or other suitable metric values.

These cars have a bad problem with leaking intake manifold gaskets. If the other ideas don't work. This is probably the problem plastic gaskets and an anti-freeze problem.

In certain gm cars as it states on the overflow tank "DEXCOOL" only, for coolant. This is a silica based application, if you use regular coolant it will east away the headgaskets(s) causing leakage and head damage.

pressure cap may be leaking preventing proper pressurization of coolant.

Thermostat may be stuck.

water pump may have failed.

1) Check the thermostatic by-pass valve: If this item is bad, it will keep open the by-pass passage so that the cooling water returns to the engine without getting to the radiator for cooling. this is required at cold start to quickly heat the engine to normal working temperature. On the water reaching ~ 60-70 deg C, it will expand to close the by-pass and clear the passage to the radiator. A Fast temperature increase (short time), usually indicates this failure. (except if the pump is completely out of commission. Normally there would be a leak on the pump and also there will be some circulation)

The simplest thing to check is the thermostat. If the engine is overheated and the radiator is cool, the thermostat is probably stuck closed keeping coolant from circulating.