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Old 09-25-2013, 07:53 AM   #1
Jkid1
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Leak down test after overheat results?

My expansion tank split while my son was driving and dumped the coolant. He continued to drive it for approximately 3 miles (30-40 mph), with the temp gauge pinned so he says. Eventually he said he couldn't accelerate past about 1200 rpm, I assume the car went to some sort of limp mode? He said it wasn't making any bad noises and I started it and rev'ed for a few seconds the next day, it ran fine. No check engine lights either, which seemed surprising. Water pours out the top of the engine when I try to fill it too.

I planned on just changing the head but decided to do a leak down test before it got that far. Not surprising, the results are between 40 and 80 percent leak for the cylinders. What I found surprising was the amount of air I hear in the oil fill cap and the dip stick. It seems like there would normally be some ( especially since it's a cold engine that has been sitting for a couple months) but it's pretty loud. Is there any way for air to be leaking in the crankcase other than the rings given the fact that my head is most likely warped and cracked? I'm starting to get the feeling that replacing just the head is a bad idea. Does it sound like my cylinders and rings are shot? Can I verify the rings at all when I get the head off?

Last edited by Jkid1; 09-25-2013 at 08:05 AM.
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Old 09-25-2013, 08:52 AM   #2
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to verify that rings are the problem I would do a compression check, get the numbers. Then add a tiny amount of oil (teaspoon or so) in the cylinders and check it again. If the rings are shot, the numbers will raise drastically.

Also, make sure that you were at TDC for that cylinder when doing the leakdown test and not BDC as that will make huge difference on where the air will go.
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Old 09-25-2013, 09:29 AM   #3
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replacing the head is often times a bad idea. I would get a used engine and follow my cooling guide next time. that's why i wrote it--so stuff like this doesn't happen. but it looks like you just signed up so never had the chance. =(
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Old 09-25-2013, 10:16 AM   #4
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That's what really makes mad. I knew these cars had weak coolant parts so I replaced everything except the radiator no more than 20k miles ago. I don't know if I got a bad reservoir tank, they're all bad or something else happened. On top of that my son very rarely drives it, so of course he had to be driving it when it blew and didn't pull over. I'll try the oil in the cylinder thing, does a compression test tell any more than a leak down test would?
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Old 09-25-2013, 10:26 AM   #5
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You would have to change the engine. Both the head and the block are made from aluminum. So both would be warped, probably beyond repair. It would just be cheaper and faster to buy a decent used engine.
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Old 09-25-2013, 10:29 AM   #6
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Quote:
Originally Posted by Jkid1 View Post
That's what really makes mad. I knew these cars had weak coolant parts so I replaced everything except the radiator no more than 20k miles ago. I don't know if I got a bad reservoir tank, they're all bad or something else happened. On top of that my son very rarely drives it, so of course he had to be driving it when it blew and didn't pull over. I'll try the oil in the cylinder thing, does a compression test tell any more than a leak down test would?
We'll never know now. Safest bet is to replace everything and bleed properly.
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Old 09-25-2013, 09:13 PM   #7
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What brand ET tank did you use?
It's worthwhile to pull the head, once you made sure the block is good,
the cylinder head job would cost less, than a replacement engine.
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Old 09-25-2013, 10:36 PM   #8
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Quote:
Originally Posted by Jkid1 View Post
That's what really makes mad. I knew these cars had weak coolant parts so I replaced everything except the radiator no more than 20k miles ago. I don't know if I got a bad reservoir tank, they're all bad or something else happened. On top of that my son very rarely drives it, so of course he had to be driving it when it blew and didn't pull over. I'll try the oil in the cylinder thing, does a compression test tell any more than a leak down test would?
I went through similar incidence 20 months and 15,000 miles ago because of popped off fan switch on the lower radiator hose.
It was overheated to the point that engine was shut off by DME.
After fixing it, engine is running good so far (knock on wood!).
You may want to replace a water pump also in addition to the heater pipes I mentioned in the following post.
Brand new water pump just before the overheat started leaking after 3,500 miles.
I think seal was damaged when engine lost coolant and water pump seal lost lubrication.

Here is what wrote after.

http://forum.e46fanatics.com/showpos...24&postcount=8

As I wrote in there, check the engine block first by torquing the cylinder head bolts. If block can not take the torque, you have a decision to make: a used engine or time-sert and head job

Last edited by dslboomer; 09-26-2013 at 12:40 AM.
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Old 09-27-2013, 03:10 PM   #9
Jkid1
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That's all good stuff to think about. I guess I might as well pull the head off and check the block for level and the cylinders for scoring and maybe cracked rings. I don't have much to lose there. Just swapping the engine out for a used one is pretty tempting though. I haven't found my receipt for the ET tank yet, I'll keep looking though. I bought the parts from a fairly large online bmw parts supplier, I just can't say which one for sure. The plastic in the tank looks different than the one I just bought to replace it with and it has very few if any stampings on it.

My leak test results seem to be sort of helpful. They are a bit inconsistent probably because of my cheap harbor freight tester, but the numbers seemed to be within 5-10% after a few readings on each cylinder. The first number is a dry cylinder, the second is after adding oil.
1: 80-40%
2: 40-40
3: 50-25
4: 55-50
5: 60-60
6: 30-40

The numbers are high but at least somewhat consistent. I'm not sure I did the first cylinder right for the first number, it was my first time with the tester and it is finicky. I could definitely hear air bubbling thought the oil after adding it to the cylinders too, much quieter. The cylinders are on a pretty good angle too so it probably makes a difference with how much oil you add and where and how much it coats the rings. At least I know I need to take a good look at cylinders 1 and 3
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