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Discussion Starter #1
Hey everyone. I've been a Camino-er for several years now, but it's been my first vehicle to really work on and trouble shoot. For that reason, I find myself learning about things as they happen (or after they happen). That's been a good educational method for the most part, but now I'm hoping that it didn't cost me a bunch of money. Could y'all give me your advice?

I was driving on I-10 East to Houston yesterday evening and noticed that the engine started running warm. It wasn't shooting up to the top of the gauge, but it was hotter than normal. Suddenly, I started to get a fuel knock, so I pulled over immediately. The engine was hot, but the radiator was cool to the touch. Thinking it was the thermostat, I pulled it out, let the engine cool, topped off the water, and hit the road. As expected, it ran a little cooler than normal, but I was running good for the next 30 miles.

Then it started to creep up again. It would get up to 200 and then drop down to 180. Then it got up to 210 and dropped again. Then it got up to 220, and I started looking for an exit (I was east of Luling, and there are only exits every 7 miles or so). When the engine started knocking again, I was freaking out, but I really wanted to get to the approaching rest stop as opposed to sitting on a narrow shoulder for an hour. I coasted into the rest stop (trying to avoid putting load on the engine), but by the time I got there, the gauge was damn near topped out at 250. Shut the engine off immediately, let my electric fans run, and opened the hood. Again, the radiator was cool to the touch, and the reservoir was full. At this point, I can only assume that the water pump is going out or I've got a clog in the system somewhere. Not wanting to push my luck, I called AAA and had it towed the rest of the way home. I'll hopefully get to work on it this evening if this rain stops.

What I'm worried about now is that I may have done major damage to my engine. It's a GM 350 Fast Burn motor with approximately 50K miles on it, and I haven't had any issues with it up to this point. As I mentioned earlier, all my knowledge up to now has been gained on a purely trial and error basis, so I'm kinda shooting in the dark.

The water pump looks easy enough to install, so I plan on replacing the pump and thermostat and flushing the system this week. While I'm doing that, what else should I look for to make sure I didn't do more damage?

I know I need to check my oil for water (currently running Royal Purple with 700 miles since the last change). But what other things would y'all recommend that I look at?

Many thanks for your help with this. I really appreciate you guys guiding a newbie along.


Much obliged,

-Steffen
 

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It sounds like the thermostat is bad. That could explain why it suddenly started running hot. Also, the radiator being cool, but the engine hot, indicates the coolant is not circulating. That seems to back up the possibility of a stuck closed thermostat.

Temperature fluctuating up and down could point to a sticky thermostat.

Running w/o a thermostat will cause the water to circulate too fast and not get cooled in the radiator. The engine then runs too hot. This is worsened by using plain water with no antifreeze, too. However, since the radiator was always cool, as you say, that complicates the diagnosis.

But, if the water pump stopped pumping (why would it do that?) the water would stop circulating through the radiator and the radiator would be cool.

I'd still suspect the thermostat. It's the easiest to change. If that doesn't fix it, change the pump.

Check for water or a milky substance in the oil. With the engine running and the radiator full, look for the water bubbling in the radiator (watch out for hot water burping out!). Either of these two can indicate a blown head gasket, but that's pretty rare on a SBC.

Jack
 

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Discussion Starter #3
Thanks Jack. Good info.

The temperature fluctuating up and down was actually after I pulled the thermostat. This was running at a constant speed and RPM, which is what made me think it was the pump. I've read before that, while not common, the impeller on the pump can start slipping off the shaft and only pump water intermittently. My thought was that the pump was circulating water part of the time and then sticking or stopping when the engine got hot. Then, since the water wasn't circulating, the radiator cooled down by the time I pulled over. That's just my inexperienced hypothesis, though, which is why I'm here.

I'll definitely try the new stat first and then look at a pump. As far as other repercussions, is there anything else I have to worry about other than a blown head gasket?


Thanks!

-Steffen
 

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Whenever I replace a thermostat I do 2 things. First I drop the T'stat in a bowl or cup of boiling water to insure that it opens. I also drill a small hole in the flange that will allow coolant to flow past the T'stat & prevent an air bubble from being trapped in the coolant passages.

Very strange that your engine temp climbed that high & yet the radiator stayed cool. I would check the main hoses for any type of debris caught inside.

When you purchase a new pump. See if you can find one that has a disc attached to the impellor like Flo-Kooler does. NAPA used to carry these types of pumps.

Good luck
~JM~
 

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Make sure that your lower radiator hose has the wire spring insert inside. If it doesn't, the hose can collapse due to the suction of the pump and cause water not to circulate. If you shut it down for a while the hose "pops" back out but will collapse again under pressure.
 

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I'm certainly no expert but my wife's buick had a similar problem. First time I pulled the water pump and there were no fins left, they had rusted away. Second time- which is more like you described - the radiator hose had a seperation on the inside and at driving speed the water would force the separation to close off the hose returning water from the engine to the radiator. The hose looked normal on the outside and at idle it was okay.
 

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To be on the safe side,replace your radiator cap.I like the basic cap over the locking cap .
 

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Make sure that your lower radiator hose has the wire spring insert inside. If it doesn't, the hose can collapse due to the suction of the pump and cause water not to circulate. If you shut it down for a while the hose "pops" back out but will collapse again under pressure.
Very, very strong possibility, and can be checked by letting it idle for a while. Also, if this isn't the cure, the impellar on the pump will be the next likely culprit. If you ever suspect air in the block, take off the radiator cap, with the cruck on an upward incline and run the engine long enough to get the air bubbles past the t-stat. Now, for antifreeze mixture vs water. Water boils at 212*, and 50-50 antifreeze boils at 227*. Now, with a pressure cap (14-15lb), that takes it up to about 230+*. That's why you use antifreeze in the summer.
 

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Discussion Starter #9
Thanks for the advice, everyone! :You_Rock:

The lower hose does have the spring insert, but I haven't watched while running to make sure it doesn't collapse. There may be a weak point on the hose somewhere.

After that, I think I'll go ahead and pull the pump and replace it. During the ordeal, I noticed a small amount of water leaking around one of the top bolt holes, so I think it's time to replace the pump anyway. I'll get a new stat as well to be safe.

After that, I plan on flushing the whole system, checking for debris, and checking all the hoses. Hopefully that will fix the cooling problem.

Other than a cracked head gasket, is there anything else I need to check for after fixing the cooling issue? I'm just worried that I might have done damage to the engine with the overheating, and I want to make sure before I start driving it around again.

Thanks again!

-Steffen
 

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for every lb of pressure you cap holds in the boiling point raises 3 degrees, if your original tstat was bad it would have spit out enough water for your sender to not read hot as it needs to have water on it to read and if your sender is in the intake instead of the head it will run out of water much sooner. to see an impeller loose is extremely rare.in 40 years of fixing cars i have seen 2 with impeller issues.start the car and let it idle with the cap off you should see a lot of motion in the water with no t stat,if you see no movement,take loose the top hose and start it to see if the radiator is clogged.it should shoot a stream of water the size of the hose at 1000 rpm. as stated above check your bottom hose,start it and rev it to about 2500/3000 rpm and watch the lower hose and watch the upper as well to see if either one colapses.
 

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Discussion Starter #11
Just wanted to give you guys an update. After tinkering around with the cruck over the last few nights, I'm pretty sure I have a blown head gasket. In fact, I'm nearly positive that the faulty gasket is what was causing the overheating.

When I checked the oil the other night, it was still clean and normal. However, when I ran the engine with the radiator cap off, I noticed what I thought was steam coming out of the top. Since I've never run a vehicle without the radiator cap, it didn't seem all that odd that some steam would come out of it.

Anyway, I went ahead an put the cap back on and kept inspecting every nook & cranny of the engine. There's a small exhaust leak where the headers bolt to the block that I've known about but wasn't too worried about. When I looked at that, there was some liquid sputtering out of the leak. Hoping I was just running VERY rich, I released the pressure on the radiator cap, and the sputtering immediately stopped. It was then that I realized that the exhaust and cooling systems were being mixed.

My new hypothesis is that the faulty head gasket is letting exhaust into the coolant loop. The exhaust is then over-pressurizing the system and blowing all the coolant out of the cap (witnessed with the old and new radiator cap). The part that's still mysterious is that the radiator was cool both times it overheated on Sunday, but I guess if all the water was getting blown out of the cap, there wouldn't be anything to actually carry heat to the radiator and it would cool off due to the fans. At least, that's the only thing I can think of.

As much as I'd like to replace the gasket myself, I think I'm in over my head at this point, and I'm probably going to take it to a shop. What are yall's thoughts?

I apologize if all of this is obvious stuff, but as I mentioned before, I'm still pretty much a rookie. I appreciate you all looking at and pondering my situation, and I can't thank you enough for your advice.


Much obliged!

-Steffen
 

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Well that pretty much about sucks.

Doing a head gasket isn't that difficult but it is a big job. I'd shop it around & see what kind of repair quotes you receive. You may decide to try the job yourself due to cost.

Good luck
~JM~
 

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Unfortunately with today's thin castings, it is as likely to be a cracked head as it is a head gasket, be sure to have the heads magnefluxed by a machine shop before you reuse them....just for the extra "warm fuzzy" of knowing for sure .....Dan
 

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Discussion Starter #15
So the first quote was $1,300 (minimum). That included 9 hours to pull the head, a machine shop testing and resurfacing it, the valve job, the new gasket, and flushing the coolant and oil systems.

Now that's just AWESOME.

9 hours of labor seemed excessive to me, but is that pretty normal?

Can anyone recommend another place in the Houston area I should talk to? I've never been one to make a decision based purely on price (since you usually get what you pay for), but I really can't afford a four-digit mechanic bill right now.


-Steffen
 

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So the first quote was $1,300 (minimum). That included 9 hours to pull the head, a machine shop testing and resurfacing it, the valve job, the new gasket, and flushing the coolant and oil systems.

Now that's just AWESOME.

9 hours of labor seemed excessive to me, but is that pretty normal?

Can anyone recommend another place in the Houston area I should talk to? I've never been one to make a decision based purely on price (since you usually get what you pay for), but I really can't afford a four-digit mechanic bill right now.


-Steffen
If that nine hours includes all of the above then its a pretty good deal, if its nine hours to pull the head OMFG! a few things though.

  • Pulling a head is not that involved an affair, if this is your daily driver then I would say find another shop or reduce the scope of the project (why a valve job on just one head?)
  • If the car isnt a daily driver I would suggest tackling this yourself, it is really a bolt on-off affair, especially with iron heads. Just make sure to have a good repair manual like a haynes and follow the instructions. - especially making sure to have thread sealant on the bolts that go into the water jacket.
  • pull the head yourself- make sure to leave the hyd lifters in their bores and make sure pushrods stay on the same valve.
  • take to a machine shop to have it checked for warpage and cracks
  • if no warpage or cracks - buy new head gasket and reinstall. make sure to rent a torque wrench
  • hyd valve adjustment isnt difficult
  • read your haynes/chilton several times and take your time and you should be fine.
You are a self-proclaimed rookie, there is no way to change that without learning something new. I say learn something new.
 

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Discussion Starter #17
You are a self-proclaimed rookie, there is no way to change that without learning something new. I say learn something new.
This thought actually excites me, and it's something I'm definitely considering. While I haven't ever done anything like this before, I'm generally very mechanically inclined, and I've picked up everything pretty quickly so far. I guess I'm just worried that I won't know what I'm looking at and either mess something up or miss seeing a problem that a more experienced eye would see.

Best case is finding someone who knows what they're doing and working with them, but all the people I know are a couple hundred miles away.

Oh well. I'll figure something out...


-Steffen
 

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This thought actually excites me, and it's something I'm definitely considering. While I haven't ever done anything like this before, I'm generally very mechanically inclined, and I've picked up everything pretty quickly so far. I guess I'm just worried that I won't know what I'm looking at and either mess something up or miss seeing a problem that a more experienced eye would see.

Best case is finding someone who knows what they're doing and working with them, but all the people I know are a couple hundred miles away.

Oh well. I'll figure something out...


-Steffen
Seriously, what you are anticipating is not a major production, especially if you are already mechanically inclined, it involves no tiny, precision adjustments, its mostly huge iron bits held together with big bolts. Time consuming yes, it can be, but for the most part its just wrench spinning.

I cant stress enough to find a repair manual - read it cover to cover several times, get yourself a copy of "How to rebuild small block chevys" read it cover to cover several times. While reading peer under your hood to indentify the items being described in the text.

It can be daunting and you are always nervous the first time you do it, but nothing beats the satifaction of firing up your motor after a significant fix like this. Dont let it intimidate you, if you can dedicate the time to it, I have no doubt you can do it. Like I said befiore, if its your primary transportation you would definitly be better served having a mechanic do it, but if you can take your time, IMO do it yourself.
 

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Take pics of how everything looks before you tear it apart. Also take pics of anything that looks odd or that you have questions about. Use plastic bags & a sharpie marker to keep parts & hardware organized. Some empty boxes will be helpful also. Keep track of where everything came from. You will want to return it to the exact same order to insure that wear patterns remain the same.

I know you don't want to hear this... but there is a chance that both heads may need to be done. Try to determine whether or not this is the case. Now is the time to find out & address it instead of finding out when you are done with one side & then need to repeat the tear down for the other side.

Good luck
~JM~
 

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Discussion Starter #20
Thanks for all the advice, fellas.

I've decided to haul the cruck a little ways down the road and work on it with a family friend. He's been a mechanic for around 30 years, and he's going to let me help (read: watch) so I can learn. The fuel and trailer rental is gonna cost a few hundred bucks, but it'll still save me a ton compared to the shop here in Houston.

I'll let you guys know how it goes and post some pics of the process. Thanks again for all the help and support!!


-Steffen
 
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