Question-------------------------
Hi Van,
Thanks for the quick and informed response to my initial question, I appreciate it. Your subject knowledge is evident. This follow-up question will be my last...promise!
I was always under the impression (I am not a mechanic, so it really is just an impression) that for overheating problems in general, that the causes stemmed from one of three general causes: first, that the coolant is low (which was not our case); second, that the circulation has stopped or slowed causing insufficient cooling; or, thirdly that, the heat is not being withdrawn from the radiator or exhaust.
That being said, I ruled out the first cause. The third cause was probably not a problem as the fan was working and the radiator seemed to be in good shape as is the exhaust system. If the second cause was noticed, the thermostat and the water pump (or possibly a blocked rad) should be verified to ensure proper flow.
I was also always under the impression that changing the coolant was more of a preventive measure. I understand that the coolant would lose its inherent properties after time and needs to be replaced under the proper maintenance guidelines, but as long as their was circulation the coolant would still withdraw heat from the engine. However, the coolant in itself should not be a sufficient cause to blow a head gasket. Another element would probably need to also be in disorder, such as a thermostat or a water pump. If the coolant is dirty and a technician suspects that this is the cause to an overheating problem, he would probably also have to suspect that the radiator is also clogged (which a simple drain and re-fill would not correct).
This is my final question: Would replacing coolant be, in itself, an effective measure for repairing an existing overheating problem and if this measure is taken, and the system is not bled causing air pockets, would this also cause overheating?
Followup To
Question -
Hi!
My wife immediately (within two minutes) brought her van into a garage after the temperature gauge indicator light went off, (the temperature gauge was slightly below the red-line). At the garage, the initial check took about 15 minutes, and they flushed the cooling system, and replaced coolant. They released the van to her saying that the problem was fixed.
She left the garage with her van and within 10 minutes the van started shaking violently. She returned the van to the garage and was informed that their was "air in the cooling system". They bled the air and returned the van to her. She returned home with the van (about 16 miles). The next morning going to work, the same shaking recurred. Again, she returned to the garage to get the van re-inspected. Again, they bled the air out of the system. Again, they assured her that the problem was settled.
She leaves for work the next day and on her way the temperature gauge starts going "haywire". The needle went up and down. Turning on the heater had no effect on the gauge, and no heat came out of the vents. She returns to the garage and they replace the thermostat, and again send her on her way.
The next morning the same problem recurs. She then calls her regular mechanic. She describes the past history and the present symptoms to him. He states that not only was replacing the coolant initially a bad move, but the air in the system probably stopped the circulation of coolant causing the engine to overheat, and cracking the head gasket, and possibly damaging the head.
We return to the initial garage to see if they could repair the van under their initial warranty (that the van was repaired). They refused to take responsibility, but would re-inspect the van. Three days later they called to say that the shaft on the water pump was loose and was the cause of the head gasket cracking. They still would not take responsibility stating that they had followed "normal" procedure. They indicated in writing that the first thing to do when a vehicle overheats is to replace the coolant. If their are subsequent problems, then, they usually replace the thermostat, and make further checks if these two things do not solve the problem.
My question is this: The water pump shaft may or may not be defective causing the head gasket to have cracked, but if this is the case, should the problem have been detected during the initial examination of the van? Could the air left in the system during the flush also be the cause of the head gasket cracking?
Answer -
Hello Shawn,
If the bearings in the water pump are bad now, they may well have been the reason for the first overheating.
That being a van, it is hard to even see the fan, much less get in there to check for free play.
The belt should be loosened to check it, so whether it should have been found then or not, is hard to say.
Initially, I would have checked the coolant level. Flushing the system would depend on the condition of the coolant, and the condition of the radiator tubes, if you can see into the rad.
If the coolant was real low, I would have filled it, pressurized it, and tried to find where it was going.
If there are no external leaks, and no coolant in the oil, yet the coolant was real low, I would suspect the possibility of a blown head gasket.
So depending on the condition of the orriginal coolant, I don't know that changing it was a bad idea.
They probably should have taken it for a ride to verify that they had corrected the problem. But if coolant wasn't leaking out of the water pump, they apparently didn't see the need to check it.
Another scenario is the possibility that a head gasket started leaking, causing the loss of coolant and the orriginal overheating, and the loose water pump shaft had nothing to do with it.
The leaking head gasket would cause the coolant to be muddy looking, and justify changing it.
Kinda like the chicken and egg question...which came first.
Just a quick item about head gaskets.
On an engine with a cast iron block, and aluminum heads, the metals expand and contract at different rates, so there is some scuffing on the gaskets, which for several years had engineers scrambling, trying to develop a gasket to handle it. They did a pretty good job, but they still cause more problems than older engines with cast iron heads.
Hopefully, in your engine, you will only need gasket replacement, and no damage occurred.
Good luck,
Van
AnswerHi Shawn,
The shop you are having questions about did NOT cause the orriginal overheating problem. It was the reason for the stop in the first place.
They may not have done what was needed to correct the problem, but then again, there is no reason to think they made anything worse.
I believe the head gasket was already blown, leaking compression into the cooling system when the engine was under load. That's what made it hot the first time, and that's what made it hot again.
They very easily could have filled and "properly" bled all the air out of the system, and while sitting there warming up, it operated completely normal.
Later, going down the road under load, the compression leaking into the cooling system displaces coolant again, and it overheats again.
Now, after the second return, they maybe should have suspected there was some other cause than some air possibly left in the system, and looked a little deeper, but that would be a separate job, not somethind covered by warranty.
You referred to it as Cracking the head gasket.
The head gasket doesn't crack, it leaks, or it blows. If it is just the beginning of a leak, compression can slip past the gasket into the cooling system, and blow coolant out by just displacing it with hot gasses.
If the engine is operated with low coolant, and gets very hot, the head itself will crack, or warp.
Since she caught it and stopped so quickly, chances are the head was not cracked.
As for the gasket blowing, it couldn't be prevented, or foreseen, and if just slightly leaking, would not show up while just warming up the engine.
And I disagree with the statement that changing the coolant was a bad idea.
Properly changing the coolant and bleeding the air would not cause any problem, and is a good idea, even though they make those umpteen thousand mile claims on the antifreeze. It still needs to be changed occasionally, and if it looks dirty, by all means change it.
I think your van had the problem before that shop ever saw it. They didn't cause it.
Van
