Bronco Forum - Full Size Ford Bronco Forum banner

1 - 20 of 30 Posts

·
Registered
Joined
·
971 Posts
Discussion Starter #1
I just ran a compression test on my 91 bronco with the 5.0 and every cylinder was over 100 but at start up and as it warming up it puffs out a little bit of smoke. Then if you rev it up when you let off of the gas it will puff a little smoke. Im also getting lots of blow by and it wrecked my air filter and covered the frame and everything near the air box with oil. I already replaced the pcv valve. The one thing that i did find was a broken spark plug but every plug seems to be burning good. So what can it be? i thought at first a bad valve guide but its getting blow by and smokes even after the initial start up. It also seems to be lacking power on the high way and hard to keep it at like 70. I swear it use to do it fine even with the 37s and factory gearing but i havnt been driving the truck as much as i use too.

Thanks
 

·
I scrape on both sides
Joined
·
3,035 Posts
If the smoke is Blue you may need to get your valve guides machined and get larger stemed valves. Also you may need to take the pistons out and check all the rings.
 

·
Registered
Joined
·
250 Posts
Puff of smoke at start up is a sign of needing a valve job. Does it smoke at high rpm's too?
 

·
Registered
Joined
·
971 Posts
Discussion Starter #4
Yea if you rev it up and let out of it it will puff out smoke. I thought it needed new valve guides until i noticed that but it also has blow by which doesnt seem like valves. And if i had a bad ring wouldnt i have low compression on that cylinder.
 

·
I scrape on both sides
Joined
·
3,035 Posts
Well with leakdown do you hear it at your exhaust or intake or dipstick tube
 

·
Registered
Joined
·
971 Posts
Discussion Starter #6
I never did a leak down test yet or do you mean when i shut the truck off?
 

·
Roller rockers are gay
Joined
·
19,191 Posts
leak down test means having the piston at TDC on the compression stroke so both valves are closed, and then injecting air (with an air compressor) with a special tool into the cylinder. you then listen for air escaping. if you hear it in the exhaust, you have a bad exhaust valve (or valve seat). same with if it's coming out of the intake manifold.

if you hear it out of the dipstick tube or oil cap, you have bad rings, or a piston with a hole in it.

what were your compression numbers?

is the smoke mostly at idle or at high rpm?

don't you also have that mustang for a DD now, or am i thinking of someone else? if it is you, the mustang is making the bronco feel slower, and you're mind ****ing yourself. the truck IS going to struggle with 37's and stock gears, and i don't believe you when you say "it did fine before." no it didn't.
 

·
Registered
Joined
·
971 Posts
Discussion Starter #8
1-125
2-140
3-133
4-135
5-125
6-100
7-125
8-140

It smokes at start up and sometimes when its warming up and then at higher rpms when you let out of it and let the rpms come back down. Then it is also getting A LOT of blow by.


And yea thats me with the fox body mustang as a DD too. And i know the truck has always been slow since i got the big tires on it but i didnt remember it being that hard to keep it at high way speeds. The fox body actually gets a little blow by to but i think thats just the set up it has. It runs no pcv valve and only one valve cover has a breather with no splash guard i guess you call it.
 

·
I scrape on both sides
Joined
·
3,035 Posts
1-125
2-140
3-133
4-135
5-125
6-100
7-125
8-140

It smokes at start up and sometimes when its warming up and then at higher rpms when you let out of it and let the rpms come back down. Then it is also getting A LOT of blow by.


And yea thats me with the fox body mustang as a DD too. And i know the truck has always been slow since i got the big tires on it but i didnt remember it being that hard to keep it at high way speeds. The fox body actually gets a little blow by to but i think thats just the set up it has. It runs no pcv valve and only one valve cover has a breather with no splash guard i guess you call it.
i'll look to see what your stock compression numbers should be unless someone beats me too it, but you should really get a leakdown test done, ecause most of those compression numbers look good except for 6 being lower than every other cylinder
 

·
Roller rockers are gay
Joined
·
19,191 Posts
eh, i'm not liking the 100psi. i also do not like that the compression is all over the place, as opposed to them all being within 5psi of each other.

like jason said, get a leakdown test done.

how many miles on the engine? you're probably looking at a rebuild bro.
 

·
Registered
Joined
·
971 Posts
Discussion Starter #11
Its pushing close to 180000 i believe and that last at-least 10,000 or 15,000 have been hard miles on 37s off road. And id like to recheck number 6 and make sure it got a good reading. Guess it might be time for a diesel swap.
 

·
Registered
Joined
·
2,785 Posts
I did a ompression check on mine in 2008, and all but #4 were 140-145 psi. This spring I re-checked #4 and got 140psi out of it. Make sure you have a good guage. Also, I have seen a motor spew oil into the air filter housing and the problem was some of the gaskets were trashed. Front, and rear main seal, timing cover gasket, valve cover gaskets, etc... Sound familiar?
 

·
Registered
Joined
·
84 Posts
is your oil level way high??? check that before you go pullin motors... your oil rings could be wiped out but your compression rings not so bad... unlikely but possible... if thats the case rebuild that sumbeach...
 

·
Registered
Joined
·
971 Posts
Discussion Starter #15
I know i got a bad rear main seal but thats been like that since the day i bought it. How would that affect the blow by? Last i checked the oil was fine. And my plan was driving it till it died then attempt a diesel swap or just have the motor rebuilt and mabe build it up a little with a cam, heads and headers. Of course gears too or sas but i have 2 unfinished projects i have to finish before i start tearing apart the bronco. I could live with the exhaust smoking at start up by the blow by is gettin old covering every thing with a nice film of oil and clogging my filter.
 

·
Roller rockers are gay
Joined
·
19,191 Posts
i don't see how leaky seals/gaskets will make a difference in the amount of blowby the engine produces. the amount has everything to do with the rings, how well they seal, and if the PCV system can handle it. even if you replaced the leaky seals/gaskets, all the engine would do is blow them out again.

you need a rebuild.
 

·
Registered
Joined
·
971 Posts
Discussion Starter #17
Thats what i was afraid of. It runs pretty good so i was hoping for a simple fix. I guess i got me a summer project
 

·
I scrape on both sides
Joined
·
3,035 Posts
Well.... If you want to go super simple just get in cross hatch honed and replace all the rigs and leave it at that so you have more money to spend on the diesel+SAS
 

·
Registered
Joined
·
98 Posts
I have the same blowby problem in my 89 351, my filter gets soaked and the housing leaks oil all over my inner fender. No money for a new motor yet, and the old one runs great. I read in here somewhere you get an oil seperater. looks like a small jar, that goes between the motor and the filter area and collects all of the oil. Thats one of my next projects. Might save you from getting a new motor, if your not ready yet. :beer
 

·
Registered
Joined
·
971 Posts
Discussion Starter #20
Well the bronco is the weekend toy any way right now so i wont even bother getting it honed out or anything. My plan is to find a power stroke f350 4x4 and swap every thing onto the bronco and throw a new paint job on it again and get the front to seats reupholstered. The body is really straight and there isnt a spot of rust any where on it including the frame. I want to make it just a cruiser/ tow rig. But that is exactly what my truck is doing the frame rail and every thing above it gets covered in oil. I was hoping there was a clog in the line to cause it to blow out instead of sucking in.
 
1 - 20 of 30 Posts
Top