: How can you tell if your HG's are shot?



Betmerick
01-06-08, 10:42 AM
I posted my overheating issue in this forum earlier and got some excellent help. I don't think my head gaskets are bad but are there tell-tale signs I should notice?

I did go to autozone and asked for the exhaust in coolant tester but the guy didn't know what I was talking about.

Also... if the gaskets are bad, how long can you drive the vehicle? With the cost of replacing them I doubt I will pay the cost and will probably junk the vehicle.

I do get a code (P0300 - misfire). Would that be a result of this or is it just a bad wire or plug and not related to the HG's?

codewize
01-06-08, 11:03 AM
Well the exhaust test is the best way to tell and be positive. that that's what the problem is.

However, coolant loss with no external leaks is a sign but that can also be the result of a leaking water crossover. Depending on how much loss we're talking about.

White smoke from the exhaust. Overheating is a sign also. If the temp continually rises during acceleration and a decreases during idle That's a good sign of head gasket. If the car just gets hot and stays steady it's probably not head gaskets..

Are you loosing coolant? How much how often?

I suppose a mis-fire could be a symptom but again, there are several things that could cause that also. Checking for gasses in the coolant is the sure way.

codewize
01-06-08, 12:20 PM
BTW whats the year make and model here. I guess I was assuming Northstar.

CadillacSTS42005
01-06-08, 01:17 PM
how can you tell?
easy
do a search and read and youll then be able to tell

Betmerick
01-06-08, 03:11 PM
It's a 1997 Deville with 87k.

Ranger
01-06-08, 09:25 PM
A cylinder pressure test will give you a positive answer. What are your symptoms?

codewize
01-06-08, 11:20 PM
Ohhh yes. I forgot that one. The old leak-down test. That will tell you also :)


A cylinder pressure test will give you a positive answer. What are your symptoms?

Zorb750
01-07-08, 12:20 AM
Uncap pressure tank while system isn't pressurized, start car, fill to proper level, make sure purge line flows correctly, slowly raise RPM to about 2000 for a couple of seconds and then slowly back down to idle (makes sure no air is trapped), put car in gear, hold brake HARD, run engine against brake slowly increasing until about 1500-1700 RPM (should be a bit over half throttle). You will have coolant bubbling out of the tank if the gasket is going, and if it's really shot, it will be EVERYWHERE if you aren't careful (hence the "slowly" part).

Easiest way of all, accurate every time I've seen it.

This test works by increasing cylinder pressure well beyond normal driving levels. Don't worry about your transmission. You aren't shearing the fluid in the TC long enough to do any damage. Powerbraking (AKA brake-torquing) causes trans problems by boiling the trans fluid through shear, overheating it. Since you are only doing this for about 15 seconds, it won't even circulate all the fluid though to heat it up. This is compounded by the fact that you are starting from a car cool enough to have the cooling system pressure drop to nothing, so the trans fluid is cool too.

Betmerick
01-07-08, 09:38 AM
I'll give that a try.

One thing I am doing is monitoring the temps on a constant basis. By doing this, I maybe setting myself up to think things I normally wouldn't think of as normal procedure wouldn't be watching the temps all drive long.

With a 20 mile trip with half on a by-pass (65mph) and half in city driving, it sits around 202-206 degrees. Now if I am stopped and let it idle for a while (5 min while at a convenience store), it will raise up to 217-222 degrees. It will drop once I'm moving again. The outside temps are in the 60-70 range (Tampa, Fl.)

Hope this info might help.

Ranger
01-07-08, 11:32 AM
Those temps sound absolutely normal.

Zorb750
01-07-08, 12:56 PM
Those temps sound absolutely normal.

What he said.

Either way, CONSISTENT high temperatures aren't indicative of a head gasket problem, they are generally indicative of a bad thermostat. Don't confuse a $25 problem with a $2500 one. If your head gasket is bad, your temps will be all over thhe map. They will skyrocket after high throttle operation, continuing to climb for a while after you let off the gas totally, they will fall like a rock if you drop it it second gear at 60 MPH with no throttle (lower cylinder pressure then under power) and fly right back up there if you get on it again before it really cools a lot, like 210 or so.

codewize
01-07-08, 04:43 PM
I agree with ranger. Those temps sound perfectly normal.

Destroyer
01-08-08, 04:31 PM
I'll give that a try.

One thing I am doing is monitoring the temps on a constant basis. By doing this, I maybe setting myself up to think things I normally wouldn't think of as normal procedure wouldn't be watching the temps all drive long.

With a 20 mile trip with half on a by-pass (65mph) and half in city driving, it sits around 202-206 degrees. Now if I am stopped and let it idle for a while (5 min while at a convenience store), it will raise up to 217-222 degrees. It will drop once I'm moving again. The outside temps are in the 60-70 range (Tampa, Fl.)

Hope this info might help.Seems normal to me as well. Thats what mine was running before the H/G's blew.

Zorb750
01-09-08, 03:00 AM
Seems normal to me as well. Thats what mine was running before the H/G's blew.

Bear in mind that operating within these ranges is not indicative that you are in danger of imminent head gasket failure. This is how they always run.

Destroyer
01-09-08, 06:58 AM
Bear in mind that operating within these ranges is not indicative that you are in danger of imminent head gasket failure. This is how they always run.
Right. I wasn't inferring that these are the temperatures the cars run right before the H/G blows. When the car was running right it ran up to 217-222 degrees.