2002 Chevy Malibu 3.1L Automatic Unusual Cooling Problem

I have a 2002 Chevy Malibu 3.1L Automatic that I’ve replaced the head gasket, intake manifold gasket, and exhaust manifold gaskets on three times in 6 years. The most recent time I think was caused by an overheating problem originally. A few weeks ago it overheated one time and boiled the coolant, but I did not let it redline on the temp-gauge. Still, the next day I found distinct evidence of coolant in the oil. After replacing the full gasket set and thermostat for good measure, I’m still getting an overheating problem. My assumption was that the coolant leaked into the oil and then when the car overheated I put only water in it temporarily which boiled somehow and probably caused more damage. This happened the first time I had a gasket problem years ago. I’m not actually losing antifreeze that I can tell, so I know it’s not the common intake manifold problem. I’ve checked all the hoses to make sure they’re all properly secure as well and I can identify no dampness or evidence of pooling. I generally run the heat to identify if my cooling system is working correctly or is at least somewhat functioning. It never does upon start-up, but I’ve found that if I rev the engine to above 4,000rpms for a sustained period of time (5-10 seconds) I can achieve what seems to be flow and the heater will kick on. The temp gauge will also level out and seem to run properly. This works about 95% of the time, but I’ve only tested it on short drives to work and back (maybe 15 - 20 miles). I’ve primed the hoses and also flushed any air from the system on multiple occasions, so I’ve tried to cover all my basis. One thing that I have noticed is that after reving it and getting it to function so I can at least get to my destination, the heater will run VERY hot. Like it will burn your hand if you hold it in front of the vent for more than a minute or two. Unfortunately, when it overheated the first time I just immediately replaced the gaskets because this was the solution the past two times, which held for about 2 years each, so I don’t know if this new, weird, problem is my doing or is something that caused the original problem. Please help, I’m stumped. I’m free to offer more details but I don’t want to be considered a “rambler.”

Sounds to me like your Temp gauge in the vehicle is telling you LIES…lol. I mean perhaps the temp gauge is not reading correctly. The heat from your heater should be Hot…but not burning hot…if it is…then so is your engine. It would be nice to have a proper temp gauge…ONe that actually tells you the TEMP and not its interpretation of Hot and or Cold… This is a common issue with temp gauges…DOes your gauge have numbers on it instead of just Hot and Cold?

YOu can go to Harbor Freight and buy yourself a cheap handheld Infra-Red Thermometer… I have one and it is invaluable in diagnosing many different issues with cooling systems and it will tell you the ACTUAL temp of your rad/hoses/ ANYTHING really…great diagnostic tool. Might be about $20 bucks?

ALSO when you stated that you replaced your head gaskets, what else did you do? Did you have the cylinder heads Straight Edged with a machinist ruler? If not you may or most likely DO have slightly WARPED cylinder heads…This would cause your Oil/coolant mixing. The new gaskets cannot make up for deviations in the cylinder head if the head is not PERFECTLY square. Are you aware of this?

So you need to find out EXACTLY how hot your engine is running either by getting an Infra red thermometer or a new separate temp gauge in the vehicle…You need to know the ACTUAL temp of your coolant. Then you can tell if you need a new thermostat or whatever… As for the oil and coolant mixing…That will NEVER go away until you have the heads checked and subsequently Machined or “cut” back to square…You new Head Gaskets dont stand a chance if you have warped heads.

This is about the most helpful response I’ve found on any site. I have a top of the line infrared laser gun here at work I’ll use on it after I get off today and maybe I can have some specifics for you. I was worried about the false reading of the temp gauge, but I wasn’t sure because it does seem move up and down fairly consistent as the engine heats up. I don’t really understand why reving the engine up for a sustained period of time would change the way the temp gauge works. Do you have any specific locations I should check, for example, the hose running from the radiator to the manifold or so on?

I really hope its not the heads, considering I took a chance on not having them machined because of financial issues. I’m always paranoid of this problem because it’s the third time so I catch it pretty quickly. I will shut off the car and leave it on the side of the road before I let it get above 3/4 on the temp gauge. That’s my personal red line. Like I said, it’s been an average 2 year life expectancy on the gasket, which seems almost common on online forums, which is sickening, but I suppose I just really don’t want it to be the heads.

How long would it take to begin leaking coolant into the oil, or at least show, after replacing the gasket? I monitor this on a daily basis by peering into my oil cap with a flash light and checking the dipstick. The oil looks clean for the most part, other than that it looks like it’s been run through an engine for a week. I actually work in the lubricants field and am quite educated on the details, looks and characteristics of oil and antifreeze. I literally sit about 15 yards from a state of the art lab, so I suppose I could draw a sample and run a crackle test.

Thanks again for your help by the way.

I read that sometimes the fins will strip of the inside of the water pump. This seems like it could cause some similar results as to what I’m experiencing. Does anyone know if there is a way I can test for this without just replacing the water pump in a wym?

Have you had the heads checked by a machine shop? This costs money, but it’s worth it to save having to do this over and over and never fixing the problem. It’s a must any time you have to pull the heads due to an overheating issue. One or both may (and probably are) warped or cracked, which will cause these problems.

I might have to address this. I suppose I’ll start crossing off the cheapest things on the list that I can check and then move to water pump and heads. I really don’t particularly want to spend another 15 hours stripping the engine down and putting it back together after I just did it a couple weeks ago, but I guess that’ll be the price I pay for trying to take shortcuts.

One other thing I thought of just after I left last time: you’re not reusing the head bolts, are you? If you are, that could explain why you have done this job three times in six years. This engine uses torque to yield bolts, which absolutely have to be replaced any time they are removed for any reason. If you have been reusing the bolts, it will never be right until you have the heads checked by a machine shop, verified good, and reinstalled with all new gaskets and head bolts. The only reason to skip the machine shop is if you find one or more obvious cracks in the heads. Valve seats are the most common places for cracks, perimeter of the combustion chamber is second, particularly between cylinders.

OK, so you are saying that after you warm up the engine normally you do not get the expected result from your heating system? If you rev the engine from a cold start to 4000rpms for what Jeez a minute…you will quickly heat up your engine and coolant to temp…Not a great idea BTW but…

It sounds to me as though…You have warped cylinder heads and or weak cyl head bolts… This is the coolant in the Oil issue. DO you also show coolant in the oil on the dipstick? Does it look like Chocolate milk? If so that’s a sure sign of oil contamination as well.

Now that you have an Infra Red thermometer…here is how we can put it to good use. I am suspecting that your Radiator may be on its way out. If your water pump impeller fell or broke off it would or SHOULD make some noise for you. Many X it is HARD water that causes Rad failure…it clogs the small passageways with minerals…thus not allowing the rad to shed heat as it should.

Start the car and allow to idle for ten minutes or so…while it is heating up and after about 3-4 minutes…feel or shoot the top and bottom Rad hoses with the thermometer… What do you get? Top hose hot and bottom hose COLD? If that is the case …it is usually due to a faulty thermostat. Now more importantly…after more idle time…say almost ten minutes. Shoot the block and then the heads and intake manifold… what are your temps? Uniform? Shouldn’t be too much deviation… Next check your hoses again…and last but certainly not least… SHoot the “tanks” of your radiator… They can be left and right or top and bottom of your radiator…depends how the mfg’d that Rad. Compare the tank temps to the thin little passage ways that run up and down on your radiator… I want you to note the temp of these little skinny water passageways within the rad itself…my temp gun has a laser dot that I can use to aim it very specifically. IF your tanks are hot and the passageways are much cooler…then you have an obstructed/blocked Rad…and need to replace the Rad… They dont cost much at all these days and is relatively easy to do…and the DO GO BAD…rather often, so it is a possibility.

So you have several things to look into…Have fun and let us know. ALso tell us about the dipstick oil check…is the oil contaminated enough to look like chocolate milk? If so that will not go away until you machine the heads and re-replace the gaskets.

***Also look into Blue Devil…IF you dont feel like tearing it down again…it is highly likely that it will save your Ass with the coolant in the oil…the stuff works very well and is a permanent fix… It goes in the Rad (your old one) very fluid “thin”…and looks like Windex…but when it encounters heat it sort of crystallizes…almost into what Hard Water looks like on a faucet…hardens like a rock and can stop coolant in the oil or coolant loss in the combustion chambers… Cost is $60 and its guaranteed… thats the only stuff in a bottle that will fix it… other than fixing it properly via mechanical means.

Have fun…Sorry for the long response. All my responses are long winded…my apologies, I am just trying to be thorough and lend a hand…

I had similar issues with my 1999 Chevy Malibu. Had to have the intake manifold gasket replaced twice! Had oil in my coolant reservoir and had to get another gasket in that car changed. I had the 3.1L V-6 engine as well.

Alright, yesterday after work, I checked a number of different suggestions. This weekend I plan to replace the fuses/relays for the cooling fan, just for good measure. I don’t really know a way to check if they are good or not other than simply replacing them, but I’ve read that this could possibly be a factor and I might as well considering my A/C hasn’t worked since I bought the thing in '06.

The oil physically looks fine. Luckily I work in an automotive lubricants plant and have a lab at my disposal. I plan to do crackle (water contaminant) testing today, tomorrow, and several days into next week to see if there is an increase in water. There may be some, on a lab scale, but I’m confident its residual from when the gasket blew two weeks ago. I cleaned it as well as I could, but I did not do any kind of liquid flush to try and eliminate absolute 100% of any remnants of water. I didn’t think I would run into additional problems at the time, but I should have known better. Isn’t there a liquid-fire thing or something that you can add that will burn off the water or is that for something else? I can say that there is no sign of any oil in the coolant reservoir, nor in any of the hoses when I checked them.

As far as the infrared testing, yes, I do have an accurate one with a laser dot as well. It looks fine from what I can tell. I checked the block, valve cover, coolant in, coolant out, and location of thermostat and they all look even for the most part and match the dash temp gauge. I will check the radiator when I crank it up to draw my oil samples at lunch today.

Another item I checked for good measure, was to see if there was any evidence of leaking from the intake manifold. This is an extremely common problem so I figured I would check into it. It looks fine from what I can tell. Everything looks sealed and there is no residual moisture. I also tried to listen to the water pump. I never particularly payed attention to it before, but it doesn’t seem to make any unusual sound, or any sound at all for that matter. Any specifics on how it would sound if the fins were stripped would help in my confidence in the pump though.

The last time I worked on it, I did not replace the cyl head bolts, nor did I machine the heads. It was a quick (15 hours) in and out job. I really just need the car to last me until next October when I plan to get a new vehicle, with minimal expenses until then.

As far as the hard water issue, I can look into it, but I highly doubt this is a factor. Our city water is rated pretty well where I live and I’ve really only dumped tap water into it once in the entire time I’ve had the vehicle. I’m an adamant user of 50/50 antifreeze which requires the water portion to pass through double reverse osmosis that purifies it to something like 99.9993% by state requirements, so I think I’m in the clear on this.

By the way, long-winded answers are welcome. The more things we can cover in detail here the more it helps me and the more it’ll help anyone else who stumbles across this discussion with the same engine. So far we’ve covered just about every common problem with this vehicle’s engine that I’ve come across in various other discussions. Maybe Car-Talk will feature this as a one-stop shop, to cure your V6 3.1L Malibu engine, haha.

Oh, yeah. A buddy of mine mentioned that it could be the heater system itself. He said that there could be a malfunction in how the engine is diverting heat to the interior from the engine and maybe something is keeping it from releasing it from the engine properly. I am not well versed in the heating system nor this process so I don’t know if this is a ridiculous suggestion or not. Any thoughts?