BHG symptoms?

[DonS1mpson]

I know that BHG threads have been done to death on here, I have searched but I'd still like a bit of input for you guys please if possible .

Long story short I bought a 91 NA that someone had been using as a drift car. The car has been used pretty hard, but was sold as being a good runner. When checking the car out I did notice a small bit of mayo on the oil cap, but then the car noticeably hadn't been driven for a long time. On the test drive the car behaved wonderfully, temp gauge read bang on the middle, I was happy enough to hand my money over and drive it home.

It was brilliant on the 2 and a half freeway journey home but as soon as I hit traffic in the city the temp gauge began to act weird. It'd build upto about 3/4 way up the scale and then drop again as soon as I got moving a bit. I pulled the the side of the road thinking the worse, attempted to open the rad cap and had coolant explode out where I just couldn't release the pressure as smoothly as I would have liked.

Now, either I lost a CRAP load of coolant on the freeway or most of the coolant had escaped the system when I took off the rad cap because I had to put in about a gallon and a half of water before the system was filled. The previous owner had mentioned that he suspected there may be an air lock in the cooling system (in hindsight that should have been a warning :3d_frown I bled the system as best I could at the side of the road.

Since then the car has been great. I drove it really, really hard the night I had the overheating drama and it didn't overheat whatsoever. A tiny bit of coolant loss, but I'm sure that could be explained by the cooling system balancing itself out via the overflow? I don't have an excessive amount of white smoke from the engine, no misfires, the car pulls well, etc. I ran the engine today with the rad cap off, no bubbles in the coolant at idle. However when I rev the engine the coolant level drops and then bubbles over the filler neck. I also noticed after a while that although there were no bubbles coolant was slowly but surely over flowing out of the filler neck - Is this a sign of the compression of the engine slowly forcing the coolant out of the radiator?

Thoughts?

 

[MPR]

Did you ask the previous owner if they had replaced the head gasket before?

Does it have an electric fan, or stock mechanical fan?

When in slow traffic, the rad isn't getting any airflow and thus the temp climbs. The fan should kick in at a certain point to keep the temp steady. If it isn't then there might be something wrong with the fan.

Doesn't sound like a BHG to me...

And removing the rad-cap on a very hot engine is not a very wise thing to do...

 

[DonS1mpson]

The previous owner had the car for the last 30,000 miles of the 100,000 miles and even with the hard usage he has put it through he hasn't touched the HG.

The cooling system is the standard clutch fan setup, however the A/C equipment has been removed, including the A/C fan.

Haven't had any issues with overheating even in stationary traffic since it over heated the first time. If I could figure out why it would have overheated the first time then I'd be more willing to put this behind me, the only thing I can think of is that the car had an airlock like the previous owner said? Then the only outstanding issue is a small bit of coolant loss that can be explained by the overflow balancing itself out.

I'd just like to confirm either way if I have a BHG or not. I can't think of any other way of confirming aside from a compression test?

 

[SRZMK3]

not a bhg you should check the wiring to the temp gauge cuz my gauge moves up and down all within seconds and nothing is wrong with the engine


yes if you took the radiator cap off the pressure would be insane in the cooling system and it would rid of the radiator storage within seconds.

if the car has been sitting for a long time there will be milk under the cap,

look for coolant smelling white exhaust,

if you are psycho paranoid rent a block tester from autozone.

 

[tyang82]

those starting happening to me last year in fall. then more and more coolant was disappearing and then the next thing. i got a warped head, BHG

 

[DonS1mpson]

You see this is precisely why I am in a dilemma. I am doubting the Head gasket, but I don't have enough proof to condemn it considering I've drove the car about 4 times. Likewise I don't want to put the car on the road and then find out 2 weeks down the line that I definitely have a blown head gasket, because then I'm losing money on insurance on a car that I'm not going to drive until I've fixed it.

Right now I think that I'm just going to risk it and put the car back on the road. If the HG has gone and it reveils itself then hopefully I'll have enough time to sort out a large enough garage so I can go JZ :naughty:

How long could a mildly blow HG last if I kept on top of temps and didn't let it overheat?

 

[MPR]

Mine ran fine with a BHG when I bought it, was just down on power a bit. Only drove it a few times, but it was BLOWN. Engine temp was always steady, it just continued to empty the coolant out the reserve while driving. No white smoke and no coolant in the oil. I got lucky and it was only blowing combustion/exhaust into the coolant jackets/system (on all 6 cylinders...lol). Compression revealed nothing as it showed 180 across all 6 cylinders!

The best way to know absolutely is to do the exhaust gasses-in-coolant test. I had a shop do it for me for $20 on the spot.

You may think the car runs fine, as I did initially. But after changing the BHG, it was a totally different car! I was like "Whoa! It does have some balls!" :biglaugh:

 

[IJ.]

Way back I had an L20b Nissan that suffered from the factory "too long bolts used in blind holes" BHG issue..

It was so bad that it would fill a cylinder hydrolocking the engine so the starter wouldn't turn it, only way to get it to run was to pull the plug crank it spraying the water out then bang the plug back in and fire it up, it ran fine...

 

[SRZMK3]

rent a block tester they are cheap and easy turn the liquid from blue to yellow and youll know but if it stays blue then your good to go.

 

[tomsupra8683]

bhg im sure.Fix it before you get water in the oil and destroy your main and rod bearings.ive had this issue twice in the last 6 months.There will be white goo on the oil cap,unusal amount of crankcase blow by and your coolant system will be over pressurized.My compression test were perfect both times but when i pulled the head you could see where the hg blew right around cylinder six.Somthing went wrong when i had the block decked.I could fix the engine but f it 2jz here i come.

 

[SRZMK3]

7mge is very easy to take apart i can do a headgasket job in 4 hours max

 

[MPR]

^lol. I guess when you've done a few it becomes 2nd nature. Took me a full weekend worth of time to do mine. But now that I've done it once, could easily do it again in less than a day.

 

[DonS1mpson]

Trying to decide between a 2JZGE swap (keeping it NA and then collecting parts to go turbo) right or just to slap a new head gasket on the 7M, abuse it for a few more months and then go 2JZ NA-T right off of the bat when the old 7M finally does give up.

I think I'm going to buy a block tester and make sure that it is actually a BHG. I'm sort of reluctant to do it though, I could buy a gasket kit for not much more $$$ .

 

[SRZMK3]

right now im abusing my 7mge and saving up for a 2jzge for swap because after that swap im pretty sure ill have enough hp to make me happy XD. rent the block tester from autozone or shucks they usually do a deposit thing where when you return it they give your money back.

 

[jenny89]

yea i would definitely check out all these suggestions. i had coolant in my oil 2 engines ago and drove it about a month ( i didnt have a choice) just dont let it overheat. mine finally did bc my temp gauge stuck a little under the middle and i thought i was good

 

[gtsfirefighter]

Mine ran fine with a BHG when I bought it, was just down on power a bit. Only drove it a few times, but it was BLOWN. Engine temp was always steady, it just continued to empty the coolant out the reserve while driving. No white smoke and no coolant in the oil. I got lucky and it was only blowing combustion/exhaust into the coolant jackets/system

My old 91 GTE was doing the exact same thing. The way I confirmed a blown HG was by doing a leak down test. I pressured up the coolant system and watched the needle very slowly go down. I then went to crank it up and low and behold if it didn't spit/sputter and white smoke bellowed out, which it had never done.

I bought a leak down tester because I knew I'd find other uses for it. It works great to help find other coolant leaks. Invest in it. I can't remember how much it was but it wasn't to bad on the pocket book.

Oh, and everybody. Please don't ruin your engines on purpose.:nono: