Block tester accuracy.

[s.u.p.r.a]

I have symptoms of a BHG but got no detection with a block tester. I tested for about 15 mins from start-up until @ regular idle temp.

Are there any other accurate ways to test for a BHG?

 

[plaaya69]

Do a compression test.

 

[james_9876]

:word8kn:

 

[s.u.p.r.a]

I'm gonna compression test tomorrow.

What I'm hoping is that all the rusty crap that was in this engine has blocked the radiator or something similar.

If it's a bhg I may have to blow up the car. :nono:

 

[supra90mkiii]

cylinder leak down test

 

[MmmBoost]

i am assuming that you are using a block tester that goes in the radiator filler neck with blue liquid that turns yellow if a leak is detected, right?

make sure that the car has been at operating temperature, and that the level of radiator fluid is a little lower than normal. you cant suck any liquid into the tester. you should leave the car running with the rad cap off for several minutes after it is 100% warmed up, then install the tester, making sure that it is sealed in the opening, and leave it for 1 minute. insert the suction ball and suck it about 5 times. make sure that bubbles come up thru the blue fluid every time you let the suction ball release, if not, its backwards.

if it comes up negative, you can do 1 more thing... remove the thermostat, and install the housing again. then let the car sit overnight so its 100% cold. start up the motor, and perform the same block test within 5 minutes. if it comes up positive then its most likely a cracked block that leaks when cold, and expands enough to seal when hot.

sorry for the lengthy posts, but i know that a lot of people misuse these testers and get false results. i use one at work several times a day and these procedures have always given me good results.

 

[Frank Rizzo]

Block testing is far more accurate at detecting a BHG than a compression test.

Did you remove the overflow tank hose from the radiator and plug the nipple when you block tested? If not, you sucked fresh, ambient air from your empty overflow bottle providing you with a false negative reading.

Do it again with the nipple blocked off.

 

[jetjock]

If you have a compressor handy you can also inject air into each cylinder and listen/watch at the rad. Still not as good as carbonic acid/ph testing though. Course, that test is only good if the HG failed into the coolant system. There are other failure modes that render the chemical test useless.

If you want increased accuracy get a dual chamber model. You'll pay the same as the one NAPA sells, which is a relic from the past. Hell, you can get a single chamber model like Napa's for half their price. Many of the newer models use engine vacuum. No bulb squeezing required. The one I have from Germany doesn't even need to have gases drawn through it and the fluid can be used over again.

 

[s.u.p.r.a]

I didn't test it at higher operating temperatures (which could be when the leak shows itself). (my thermostat is temporarily out so I couldn't get much hotter @ idle)

I see what compression test results I get today and post 'em.

 

[bfr1992t]

Do you have "no t-stat" symptoms instead of BHG symptoms?

 

[Frank Rizzo]

The normal stock 7M head gasket failure is almost 100% combustion chamber-to-coolant passage. That is why I said more accurate than a comp test. As far as aftermarket head gasket failure, the same rules apply as with all engines, do a leakdown test. Which involves injecting air into the cylinders as jet described, listening for leakage between cylinder.

 

[s.u.p.r.a]

K, didn't get a chance to pressure test but am I am pretty sure that my ~50,000 mile engine came with a BHG.

If I take the head off what are the chances I can drop a new stock hg on and be fine? Since the leak seems to happen once the car has been driving around for a while would it suggest that the leak isn't too bad?

EDIT: If my thermostat housing was leaking a tiny tiny bit then could it cause the coolant to steam out of the overflow?

Thanks for the info.

 

[Frank Rizzo]

Leaking thermostat housing does not = coolant pissing out the overflow. Over pressurization from 150+psi combustion chamber gases are leaking into the normal 15psi pressurized coolant causing coolant to fill up and come spewing out of the overflow.

(The following assumes you have no cracks in your head or block and no warpage) You have to mill the head and prep the block by hand at LEAST. Best case scenario is having a machine shop deck the block. Hand lapping the block is your best bet for just a stock rebuild. Have fun and good luck, you need that when working on a 20 year old, low production # vehicle. That and a fat ass bankroll.

Didn't you know? 7M's came stock with a blown head gasket. It's right there in the owners manual......

 

[s.u.p.r.a]

I'll pull apart the head today and post some pics of the gasket -- If an engine company shipped me this engine a couple of months ago would they be at all responsible for a BHG? They are in canada so they have to follow the stricter sales rules.

 

[JAB89]

Have you pulled the head off yet? Do you have access to an air compressor as JJ suggested? If not, you can even use a portable air tank and an electric tire pump.

Pressurizing each cylinder (at TDC) is a very definitive way to confirm your suspicions of a BHG. Also, a hell of a lot easier than pulling the head off. In fact you can get to the spark plugs in the early part of the tear down.

As far as any HG warranty on a JDM engine, I seriously doubt it. Those people know the reputation of the 7M. And besides do you want to pay shipping both ways for another questionable engine? What's that, about $400? I think I would just fix the one you have.

Good luck though, you can fix this.

 

[bfr1992t]

Didn't you know? 7M's came stock with a blown head gasket. It's right there in the owners manual......

7M's are bought by stupid owners...

He said "coolant steam out of the overflow", not "stream out of the overflow".

Yes, any leak could let air back in, which could eventually make it's way out of the overflow as the system cycles.

He also has no thermostat. That's a BIG problem right there.

But it seems nobody is listening so the original poster can go pull the head, tear the gasket in the process and the leftover coolant in the head will drain in to two cylinders, thus creating one blown headgasket.

Or he can try a leakdown test, or fix any leaks, put in a functioning OEM thermostat and maybe replace the radiator cap (again w/ OEM), and then see if his "symptoms" are gone. Both are simple and much easier.

 

[s.u.p.r.a]

BHG -> http://www.supramania.com/forums/showthread.php?p=845601#post845601

 

[Frank Rizzo]

Classic oval cylinder part of the gasket with collasped exhaust coolant passages of the gasket.