Car Won't Start, Very Low Compression

[360glitch]

After finishing up installing a new head gasket last night I departed this morning on a 100+ mile trip to race the car at an autocross event today. 20 miles short of my destination, the I saw the car start to overheat. As soon as I saw it, I turned the car off and pulled off of the road. I had been keeping a close eye on things and know for sure that it had not been running hot for a long time or anything. After opening the hood I quickly saw a coolant line that had blown so I replaced it, no big deal.

But then, the car would not start back up. After doing a good bit of testing I've confirmed spark and fuel. I did a compression check and found very low compression across the board. 80-90 on all four.

The best theory I currently have is that maybe the mechanical timing somehow jumped a tooth? I've read that the timing being off can cause the compression readings to be low. Could it have jumped while I was driving and I not even notice? Any other theories?

 

[delta448]

Bad headgasket. Your compression is going into the coolant passages and that's why your hose popped off.

 

[360glitch]

Bad headgasket. Your compression is going into the coolant passages and that's why your hose popped off.

I just cannot imagine the headgasket failed. I literally finished replaced it yesterday. New headgasket, freshly resurfaced head, ARP's torqued down in the correct order nice and tight. It ran great after I finished and up until this occurrence.

 

[delta448]

Just curious, -did you retorque after a heat cycle?

In the greatest likelyhood, this is your problem, but there are some other possibilities. Two things that would help eliminate the variables would be a proper leakdown test and verifying the cam timing.

 

[360glitch]

Just curious, -did you retorque after a heat cycle?

In the greatest likelyhood, this is your problem, but there are some other possibilities. Two things that would help eliminate the variables would be a proper leakdown test and verifying the cam timing.

I did not retorque the bolts. Is it too late to do so?

 

[MichaelSuch]

With 80-90 on all 4 cylinders it should start, I'm running a car with 60 in one cylinder and about 100-120 in the rest. I read the material that came with my ARP studs that they shouldn't need to be retightened as long as you used the moly lube provided and that it was torqued to spec.

First off I would check the timing and make sure it is properly set, otherwise another headgasket job may be in order for you.

Edit: Did you use copper spray on the previous head gasket or anything?

 

[90rslaser]

yes your car can jump a tooth or 2 aND you wont notice it until you turn it off then try to start it back up. you are probably blowing boost into your hoses do to a bad head gasket. and like said before, not retorqing aftewr heat cycle can make things aa little weary. you probably now have bad valves

 

[360glitch]

No copper spray on either of the gaskets. I'm going to pull the timing covers today and check the mechanical timing, and then go from there.

 

[jrohner]

I saw the car start to overheat. As soon as I saw it, I turned the car off and pulled off of the road. I had been keeping a close eye on things and know for sure that it had not been running hot for a long time or anything. After opening the hood I quickly saw a coolant line that had blown so I replaced it, no big deal.

No big deal? It's rare that overheating is "no big deal".

I just cannot imagine the headgasket failed. I literally finished replaced it yesterday. New headgasket, freshly resurfaced head, ARP's torqued down in the correct order nice and tight. It ran great after I finished and up until this occurrence.

It doesn't matter if the head gasket has been in for 5 hours or 20 years, overheating will wreck it just the same. If a line went, all your coolant dumped. Water temp gauges were not designed to read air temperature (an empty cooling system), so they don't read correctly when there is no coolant left -- so you could've been cooking the engine for who knows how long.

If it got really hot, your rings are probably fried too, and that could actually be what's causing the low compression more than anything. Compression could be leaking out the rings, head gasket, or a combination of the two.

Have fun rebuilding.

 

[delta448]

^Agreed.

There are a few different ways to look at it, whether the HG went first or the coolant hose, or if the t-belt indeed jumped and caused extra heat; but the end result was still overheating and low compression. Either way you're going to be pulling the head to fix it. Make sure the t-belt and tensioner are good, check the head and deck surfaces for warpage, and buy a new headgasket (and or rings, per the results of your leakdown test).

 

[360glitch]

No big deal? It's rare that overheating is "no big deal".



It doesn't matter if the head gasket has been in for 5 hours or 20 years, overheating will wreck it just the same. If a line went, all your coolant dumped. Water temp gauges were not designed to read air temperature (an empty cooling system), so they don't read correctly when there is no coolant left -- so you could've been cooking the engine for who knows how long.

If it got really hot, your rings are probably fried too, and that could actually be what's causing the low compression more than anything. Compression could be leaking out the rings, head gasket, or a combination of the two.

Have fun rebuilding.

Thanks for the encouraging words.




I do appreciate the information, but there are nicer ways to go about saying things.

 

[nuclearr]

Also because of where the temp senors are located if you are running low on coolant the sensors do not pick up water temp they read the air in the coolant system or pick up gradual heat from the thermostat housing. I blew a few head gaskets on several mitsubishi's mostly on 1.5's and 1.8's but the design is the same (untill I fugured out the sensor issue). When I put my new car back together I am going to have to find a way to put in a tepm senor lower in the system so I can have two gauges to go buy ranter than just the stock one.

SO DONT TRUST THE GAUGE!!!

EDIT: I also blew up a 1.8 b/c of this issue a week after I got the dang thing running and the first day on the road.

 

[jrohner]

Thanks for the encouraging words.

I do appreciate the information, but there are nicer ways to go about saying things.

?

I was just stating the facts. Sorry you took it differently, but I was not being mean to you. Your engine got cooked and the only possible positive to look forward to is if your rings are not shot too.

 

[Fiascoxl]

You stated that you couldnt get the car to start so you did a comp check? If so then you did a comp check with the car cold, this may be the reason you have such low numbers. Comp checks should be done with the car at operating temp.

 

[brassc2007]

a compression test can be done when the engine is cold it is just suggested to do it at running temp when the rings have expanded the little bit they do when the car is warm the numbers may be a little lower but you can take a teaspoon of oil and put it into each cylinder and that will give you a more accurate number.