Ive got a 87 Bronc 5.0 that was running really rough, and blowin white smoke. So, I changed plugs,wires,cap & rotor and not much changed. I Was advised to do a compression check, and when I did found that cylinder #2 had about 5 psi while the other 7 had about 170. Now, I know this isnt going to be an easy job, but its something I'll have to do myself, due to lack of funds. With limited experiance. So, I guess what I would like to know is, can or should I just fix whats wrong with cylinder #2? Instead of a complete rebuild So I can get "Blue" back on the road. I have another 5.0 in a 90 bronc,(parts truck) it's a Jasper with about 70k on it. But, it's been sitting for about 3yrs. I hope to rebuild that one in time. Something I don't have alot of right now. THANX for any info !!!

 

Low compression on 1 cylinder could be stuck or broken rings, a broken piston, a burnt or broken valve, or a blown heat gasket.. but there's no way to know until you look. If you're getting white smoke out the exhaust you have coolant in the combustion chamber, so that points to a head gasket. If you can swing a wrench and follow proceedures in a service manual you can change a head gasket.. it's not that bad. However... it's a bit of a gamble to take the motor apart because you may find more than just this 1 problem, and if you do, swapping in the spare motor you have quickly becomes a lot less work. Might be a good idea to squirt some oil into the cylinders on the other motor and do a compression check on it before you tear into this motor.

 

THANX! Conanski, I can turn a wrench, But don"t read well. Yesterday I took off intake, headers,wires hoses ect. Working my way in. But I don"t have a garage and it"s gonna rain today.So maybe tomorrow, And besides it's my BIRTHDAY! Anyway, you said something about #1 and the pressure is down in #2. So does everything you said still apply

 

Sounds like good advise, But not sure how.(maybe explain?)And I've taken alot off the 90 in the past, including (trans, starter, exhaust,(headers) alt. distributor,radiator & plumming, ect). And I'm wondering, If it would be MORE work to get the 90 ready to test, or just dive into the 87 ("BLUE") And rebuild the 90 when I've got the money & time to upgrade (heads intake cam ect.) during the process. And after lookin closer I saw where you said "1" cylinder not #1. Sorry.

 

These motors are pretty durable in general, you will probably have to do nothing but change the head gasket and it'll be good as new. When you get it apart check the cylinder wall for obvious damage, inspect the head for obvious problems like broken springs, valve stem seals, etc. You can also do a quick and dirty test to see how well the valves are sealing by flipping them upside down and filling the combustion chamber with water or light oil. If any gets by the valves and drains out the ports the valve seats are shot. If you only get a tiny amount of sepage from a valve you can clean up the seats with some lapping compound...search valve lapping on the web. It's a simple proceedure that just requires you remove the valve, apply some compound to the seat and work it against the valve to restore an even mating surface.

 

THANX again! This all sounds very doable. I'm really not much of a mechanic and don't know how to diagnose. But I'm learning how to work on my own truck, And I'm diggin it! It's worth the work, Real nice looker. Also new to PC,s but hope to learn how to put pics on soon. However it's got push button transfer case & autohubs, Planning to switch to manual (both off 90) this summer. With the help of FTE,s of course. This site is GREAT!!!

 

I just found a rebulit cylinder head #D80E new guild liners,seal & keepers, for a good price. Will this fit my truck? And would it save me any time over fixing the things you said above? Or do I only need that if the head itself is cracked? Sorry so many questions. Just tring to learn something. Again, any info appreciated.

 

Also, when I take off the head to see whats wrong. Will I have to have it machined to reinstall?

 

Learn how to use a leak down tester and you will save yourself hours and days of time, it is by far the best tool to have at you disposal.

Here's how it works, you said #2 cylinder is the one with low compression.
The leak down tester looks sort of like a compression tester but you need an air compressor to use it.

First you bring the number 2 cylinder to top dead centre(that's how we spell center in Canada LOL) then you screw in the leak down tester all the directions are on the package it comes in.

But once you've screwed it into the number 2 cylinder and that cylinder is at top dead centre and you have the compressor hose hooked up to the leak down tester you open the valve on the leak down tester.

The next part is really easy you listen for air.

If you hear air coming out the tail pipe it's the exhaust valve that's your problem, if you hear air coming out the intake plenum it's the intake valve that's your problem, if you see bubbles coming out of your Rad it's a head gasket or head cracked problem, and if you hear air coming out of the dip stick it's the piston rings or damaged piston problem ie a hole burned through the piston.

Didn't I tell you it was the best tool money can buy?
And they are only $30 to $60 dollars to buy and it saves you from having to pull heads to see what the problem is.


Cheers,Rick.

 

Sounds like a real time saver to diagnose the problem. Can I still do this after removing the upper intake, headers,& radiator hose at termostat? (I've already done these things) And I still have to take the head off to fix any of those problems anyway. Right? Any info on if it's necessary to resurface the connecting areas (where gasket goes)before reinstaling, "IF" it turns out to be valve or gasket or piston & or ring and not a cracked head?

 

You just have to listen for the air at a closer spot, and yes it is the biggest time saver, I never remove anything until I've leak down tested always heads you in the right direction in the shortest time.

Cheers,Rick and good luck.

 

Yes, I "WILL" remember that next time. I'm still learning. But what about resurfacing?

 

And also,where did you find this "leak down tester"? When I call places they don't seem to know of anything by that name. Even after I discribe what it does. They just have the compression tester that I've already used in the sparkplug hole. Does it maybe have a more technical name?

 

Here's a nice link.. How to do Cylinder Leak Down Testing- Car Craft Magazine

All you really need is a fitting to attach an air compresor hose to the spark plug hole, and then you listen or feel for excapeing air from the valves and other places Rick mentioned.
Unless you severly overheated this motor I doubt you damaged the head, it may be an idea to have it magnafluxed for cracks if you have access to a machine shop, but the risk isn't high IMO.
The D8OE head doesn't match the other head you have in terms of combustion chamber size so it's not a good substitute

 

I see you're in Ottawa are you a member of the Ontario Board?

I don't remember seeing any of your posts on that board.

Cheers, Rick.