Think I have my 1st bhg

[zman6127]

So I started having cool air when the heat was on and temp gage would rise and then blow hot air again. Also started hearing air bubbles behind the dash. I bled the coolant system and put new rad cap and tstat in since the car had been in storage for 6 months. Everything seemed fine after doing that an test drive went well and had her the whole time and gage stayed normal temp. Then when I got home I realized the coolant overflow tank had boiled over and was full to the top. I work at a body shop as an estimator and the one mechanic that works there with me is an old school Toyota guy ( land cruisers in particular). He worked for a shop here in town in the 80's that specialized in land cruiser and mk3's. I left the car at the shop that night and he put dye in the system. I came in the next morning hoping that he had successfully bled the system and everything would be ok. He told me that the coolant is only flowing out or on way in the engine and he suspected the beginning of a bhg. No milking dipstick, non on the oil cap and the plugs are clean. Some how air is getting in my system and I now do think bhg and I caught it before it got bad. Now my car is a 90 7mgte 5spd with 120k miles. I am the second owner and it is super clean and well cared for. What do you guys think? Mileage wise just time that it finally bhg or any other ideas. The coolant resivor has boiled over three times now but the car has never overheated yet. Also is there a head gasket kit out there that comes with a metal hg so all else I have to buy is arp head bolts.


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[emericaskater285]

Mine went at 78,xxx miles or so. Did the same thing, put air into the cooling system. Mine did overheat tho. I would imagine you are starting to have a BHG, and would do a compression test on the engine to see.

 

[zman6127]

Yeah it sucks for sure! At least it's still cold here and I don't depend on it for a dd! I also just read in the discussion area that I shouldn't use a mhg if I'm not going to machine the block. And I'm not I'm jut gonna take the head I machine shop. I plan on keeping this one prettying stock except for intake, exhaust and wheels and tires. Composite hg should be just fine then and ill buy arp head bolts


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[emericaskater285]

I would recommend flushing the oil and coolant after you get it back together, and drive it as little as possible, because if you get coolant into the oil it will cause rod knock, which will mean you will have to have the whole block redone and everything.

When I say drive it as little as possible, I mean either drive it home or trailer it home and park it until you can get the BHG fixed and all. When the coolant is pressurized by the engine when it is running it will be fine as long as its not overheating, but when you shut the engine off it will cause the coolant to be the pressurized system, thus causing the coolant to flow into your combustion chambers and sit on top of your pistons. The coolant will leak past your piston rings, and into your oil, this will eventually lead to rod knock. Once your car knocks it is all over.

This is a common problem on 7m's and I know this has happened on many other vehicles. I have seen this on diesel engines and others as well.

 

[zman6127]

It's staying at the shop and will be worked on after hours. I'm fortunate my boss likes me and is ok with us working after on it and keeping it there where all the techs tools are. I told him anywhere from a couple weeks to a month since we are just working a little at a time. I'm hoping to get it done with parts an paying the mechanic for his time to come in between $800-$900.


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[jonahs_supra]

Yuh tale tale signs of bhg
Once you pull the headgasket youll find that 1 cylinder and pushing exhaust gasses into the cooling system

 

[emericaskater285]

It's staying at the shop and will be worked on after hours. I'm fortunate my boss likes me and is ok with us working after on it and keeping it there where all the techs tools are. I told him anywhere from a couple weeks to a month since we are just working a little at a time. I'm hoping to get it done with parts an paying the mechanic for his time to come in between $800-$900.


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Good choice man. I am glad to hear you wont be taking it on the road until it is done. There have been too many people that drive it after seeing the obvious signs of BHG.

 

[zman6127]

Does anyone know if the cometic head gasket set is a metal hg in the kit! Every site I see that sells it shows a generic pic of a 4cyl head set and doesn't say that it's a metal hg in the kit. I don't wanna buy a head gasket set then spend another $120 or so on a mhg


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[Doat]

I used a Felpro head gasket kit they assured me that their composite head gasket is the same or better than OEM but I would get better gaskets for everything else that you will replace as you remove the head. I used the Felpro kit with ARP head studs on my 7M and did the entire job myself, I have a thread about it on here if you are interested, it's really not difficult it just takes time and be careful with marking your parts and bolts I tagged and bagged everything. I still do not have any head gasket issues about 4 months into it now from when I finished the job maybe more and never had a problem with oil pressure, coolant temp, no rod knock except for on cold starts for a sec or two but apparently that is normal because there is no oil in the cylinders on cold starts.

 

[zman6127]

Felpro kit with arps is probly the route I'm going. I'm waiting to get the head off and over to the machine shop this week before ordering parts


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[zman6127]

Just to make sure I don't need anything else.


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[Doat]

I would take this time to also replace your valve stem seals while you are at it and just clean everything the block, EGR valve, throttle body, etc. just take the time to spray some stuff down with carb or brake cleaner and scrub it down well it will be worth it in the end and less of a chance for something to get blocked up or anything like that. When you put the ARP studs on if you put the studs into the block first then drop the head in be very careful when you drop the head down onto the block through the studs to not scratch the head or what you can do is put the head on first then put the ARP studs in and tighten them down hand tight but I put the studs in first because it was easier for me to hand tighten them and I found it to help get the head lined up perfectly with the gasket and block for a good seal. Just take your time to clean everything especially the threads in the block before you put the studs in so you get an accurate torque reading and no chance of something going wrong. Take your time and clean as much as possible and you will be fine. I used engine assembly lube for the cams when I cleaned them up and put them in and if your block is going to be exposed for awhile I would coat it and the pistons in oil or what I did was coat them generously in Mystery Oil then put saran wrap on it but that was because my block was exposed for a good few weeks and here in Houston it gets hot and humid but I would do it anyway to be on the safe side.

Also replace your vacuum lines while you are at it and BE VERY CAREFUL FOR THE EXHAUST STUDS I cannot stress this enough but either way it's probably good to helicoil your exhaust manifold threads in the head anyway to make them stronger because odds are they will get stripped when you take it off 7Ms are notorious for stripping the exhaust manifold threads. It's really not that difficult just be slow and careful when you re-thread it and you will need to buy a short drill bit to drill out the exhaust stud right by the firewall and short 90 degree drill as well. I also went ahead and bought new exhaust manifold studs and nuts from the dealer along with a few other bolts and nuts.

I suggest going through my head gasket thread for some tips, tricks, and advice I tried to post as many pictures as I could.
http://www.supramania.com/forums/sh...sket-me-asking-for-your-help-while-doing-this

 

[zman6127]

Ok I will check it out thanks buddy


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[Doat]

No problem man that thread is filled with good info and I am visual person so I like seeing what I am talking about. Also check out Numba1stunna's youtube channel his videos helped me out a lot with lapping the valve seats, installing valve stem seals, etc.

 

[Grandavi]

Yeah, Felpro will do you and definitely is all the symptoms of a headgasket. My 90 just did the exact same thing about 3 weeks ago. Pulled the head, checked everything out and if I was keeping the car, there's no way I wouldn't have decked the block, rebuilt the head and done metal with ARP studs. This was a "flipper" though, so I did the Felpro route, cleaned the block surface, checked it for straightness, looked over the head closely, fixed the EGR (they always seem to leak), replaced a LOT of hoses and just reused the stock headbolts.
Car ran like a champ afterwards (caught it early enough, there was no damage to bearings, etc... The headgasket went, the car drove for about 10 minutes before I realised it, so all was good, never overheated.
Sold the car 3 days after I got the headgasket redone. It should be solid providing they retorque at specified maintenance level (I think thats 50,000 km, not sure).

If I was keeping the car, the only reason I would go metal headgasket is because if its done correctly, the headgasket is pretty well bullet proof. No more worries.

Oh.. and I would recommend looking very closely at all the wiring in the harness. Perfect time to recondition it (which I also did). If you ignore it, you may end up with little troubles later that are hard to trace down because your harness will be old, dry and cracking in certain areas simply due to age and heat. Also a perfect time to replace and/or upgrade the coolant lines near the rear of the engine. Its a pain to do later on, but with the head off, its not nearly as much work. Definitely worth the investment.

 

[Doat]

Very good point, yes replace the coolant hoses and such that run toward the back of the motor MUCH easier to do with the head off.