95 overheating experience
Gigantor-LS
10-24-2005, 10:48 PM
Hello folks. I've been reading the forums for a while. Thought I would register and share a few experiences that I've had with my 95 MC. It's an LS 3.1 with about 105k miles. Bought it when it had 50k. It's been paid off for about a year now.
Back in January, I had issues with it overheating. I would loose heat from the dash and the car would start overheating. My first thought was thermostat, but if it was stuck closed, I would still get heat from dash. I then thought maybe the water pump was bad.
I was fairly new to Lansing Michigan, so I wasn't sure where I could find a reliable mechanic. I took it to a place and they told me it was the water pump was rotted inside so they replaced it. A few days later, I had the same problem. Took it back and they decided that the thermostat should be replaced. To get to it, they needed to pull the intake manifold off. They found that the gasket for the manifold was shot. I thought that the bad gasket might explain why I was getting air buildup. They replaced the gasket and put a thermostat in. A few days later, same problem.
After hundreds of dollars, I decided to find a "mechanic", not a "parts changer". I spoke with a co-worker and he recommended a shop to me. I took the car in and they took a look at it. They found that recently installed gasket already blew out and there was some pitting on the intake. Instead of having to buy a new intake, they applied an epoxy and sanded it smooth. They said I should get about 25k miles out of it, but the gasket would probably go again. They also found that the computer was so corroded, it has split open. It wouldn't be accepted as a core because of the damage. They replaced it and had to run a few new wires.
Well, no overheat problems for 9 months or so, until yesterday. I popped the hood and found that there was a buildup of air in the radiator again. I also saw oil in the coolant and sludge in the reservoir. Crap...head problems. I checked oil...no gunk or signs of water beaded up.
Took it back to the shop. They said the oil was fine but I had "gunk buildup" in radiator. Because I gave them a ton of business less than a year ago, they flushed the coolant system and replaced the thermostat for free. They were afraid the stat was fouled up from the sludge. I picked up the car and had a gander the stat. Nothing wrong...I figured it was OK. I asked if they ran a compression test. They explained that they usually don't do that with an intake manifold replacement. I told him I thought it might be a head gasket problem. He explained that if it was the head, there would be coolant in the oil.
Got to work and thought I would do some investigating of my own. I found an article. Litt's Overheating Hypothesis (http://www.troubleshooters.com/tlitthypothesis.htm). Here is a quote that I found interesting.
I've spoken to several mechanics and found that few believe this hypothesis. For one thing, many of these cyclical overheats occurred without evidence of coolant in the oil (yellow gunk around the oil cap) or coolant in the cylinders (profuse white exhaust, especially on startup). As one mechanic put it, "a broken head gasket is a two way street". The idea is that once the engine is shut off, the coolant pressure will exceed the cylinder pressure and force coolant into the cylinders and oil.
I'm not so sure. Envision a head gasket defect so small that it acts like a valve, opening only above, let's say, 50psi. The cooling system bleeds at much lower pressures, so the transfer would be only from cylinder to coolant, but not the reverse, even when the engine is shut down.
Most of the readers submitting these symptoms have been to one or more mechanics, and typically had spent several hundred dollars replacing components. Most overheats are caused by clogged radiators, low coolant levels, bad water pumps, inaccurate thermostats and the like, so a mechanic can successfully diagnose and fix over 90% of overheats without ever considering a broken head gasket. And most broken head gaskets leave obvious clues such as yellow gunk on the oil cap or billowing white exhaust. I believe this is why most mechanics reject this hypothesis.
Now, I take everything with a grain of salt, but this article hits my car issues right on the head. I can tell that there was oil in my coolant. I had it flushed 8 months ago, and now there is a visible film in the reservoir and under the cap. Clumps that almost look like tar were under the cap. The mechanic I talked to does not think it's a head gasket...but I'm not so sure.
The article mentions a combustion gas tester. I don't want to drop $45 on one, but I would guess that the gas buildup in the coolant system is coming from the head. The guy at the shop told me to bring it back in if there was still a problem. If there is, I am paying him to do a compression test. I got to know if the head is the problem.
Anyway, just thought I would write this out just in case someone else runs in to a similar issue.
Back in January, I had issues with it overheating. I would loose heat from the dash and the car would start overheating. My first thought was thermostat, but if it was stuck closed, I would still get heat from dash. I then thought maybe the water pump was bad.
I was fairly new to Lansing Michigan, so I wasn't sure where I could find a reliable mechanic. I took it to a place and they told me it was the water pump was rotted inside so they replaced it. A few days later, I had the same problem. Took it back and they decided that the thermostat should be replaced. To get to it, they needed to pull the intake manifold off. They found that the gasket for the manifold was shot. I thought that the bad gasket might explain why I was getting air buildup. They replaced the gasket and put a thermostat in. A few days later, same problem.
After hundreds of dollars, I decided to find a "mechanic", not a "parts changer". I spoke with a co-worker and he recommended a shop to me. I took the car in and they took a look at it. They found that recently installed gasket already blew out and there was some pitting on the intake. Instead of having to buy a new intake, they applied an epoxy and sanded it smooth. They said I should get about 25k miles out of it, but the gasket would probably go again. They also found that the computer was so corroded, it has split open. It wouldn't be accepted as a core because of the damage. They replaced it and had to run a few new wires.
Well, no overheat problems for 9 months or so, until yesterday. I popped the hood and found that there was a buildup of air in the radiator again. I also saw oil in the coolant and sludge in the reservoir. Crap...head problems. I checked oil...no gunk or signs of water beaded up.
Took it back to the shop. They said the oil was fine but I had "gunk buildup" in radiator. Because I gave them a ton of business less than a year ago, they flushed the coolant system and replaced the thermostat for free. They were afraid the stat was fouled up from the sludge. I picked up the car and had a gander the stat. Nothing wrong...I figured it was OK. I asked if they ran a compression test. They explained that they usually don't do that with an intake manifold replacement. I told him I thought it might be a head gasket problem. He explained that if it was the head, there would be coolant in the oil.
Got to work and thought I would do some investigating of my own. I found an article. Litt's Overheating Hypothesis (http://www.troubleshooters.com/tlitthypothesis.htm). Here is a quote that I found interesting.
I've spoken to several mechanics and found that few believe this hypothesis. For one thing, many of these cyclical overheats occurred without evidence of coolant in the oil (yellow gunk around the oil cap) or coolant in the cylinders (profuse white exhaust, especially on startup). As one mechanic put it, "a broken head gasket is a two way street". The idea is that once the engine is shut off, the coolant pressure will exceed the cylinder pressure and force coolant into the cylinders and oil.
I'm not so sure. Envision a head gasket defect so small that it acts like a valve, opening only above, let's say, 50psi. The cooling system bleeds at much lower pressures, so the transfer would be only from cylinder to coolant, but not the reverse, even when the engine is shut down.
Most of the readers submitting these symptoms have been to one or more mechanics, and typically had spent several hundred dollars replacing components. Most overheats are caused by clogged radiators, low coolant levels, bad water pumps, inaccurate thermostats and the like, so a mechanic can successfully diagnose and fix over 90% of overheats without ever considering a broken head gasket. And most broken head gaskets leave obvious clues such as yellow gunk on the oil cap or billowing white exhaust. I believe this is why most mechanics reject this hypothesis.
Now, I take everything with a grain of salt, but this article hits my car issues right on the head. I can tell that there was oil in my coolant. I had it flushed 8 months ago, and now there is a visible film in the reservoir and under the cap. Clumps that almost look like tar were under the cap. The mechanic I talked to does not think it's a head gasket...but I'm not so sure.
The article mentions a combustion gas tester. I don't want to drop $45 on one, but I would guess that the gas buildup in the coolant system is coming from the head. The guy at the shop told me to bring it back in if there was still a problem. If there is, I am paying him to do a compression test. I got to know if the head is the problem.
Anyway, just thought I would write this out just in case someone else runs in to a similar issue.
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