1000rrstunna

Soo I just bought a 91 to do a trail build on. My 99 is way to nice to cut up and this one is in great shape minus a few small issues it has 110k miles and was a one owner truck! I bought it from a local repair shop that got it from the original owner once they told him it needed a head gasket... I honestly think they don't know what they are talking about... The truck will idle for over 1/2 hour and never go over 210 they never performed a leak down test either according to the guy who worked on it... So knowing this I drove it 5 miles home never broke 210 parked it and let it run for a 1/2 hour with no indication of an overheat I did however notice the electric fan does not come on at 210 on the dash... The radiator water pump and fan clutch are original... There is no coolant in the oil it doesn't smoke and it runs strong... I'm not a believer that there is a head gasket issue what so ever... Was thinking about buying a radiator water pump and thermostat and fan clutch at autozone flushing heater core and everything and seeing what happens... I'm also going to go take it for some hot laps around the subdivision to see if I can get it to overheat.. If it gets hot ill park it walk home and come back later... I feel like I need to experience what happens I order to see the issues instead of taking somebody's word for it

Any suggestions helpful.

The trucks really nice for a 91. Ac even works! And it's got power seats!!

1000rrstunna

Pretty nice for a 91...

1000rrstunna

Well I just took it for a hot lap. After she reaches 210 it keeps climbing and the electric fan was on..... Went to pep boys got the rad, water pump, 195deg therm and fan clutch plus gaskets..... Have some coolant here let the adventure begin... I think the radiator is full of crap or blocked personally

djb383

Take the old rad out 1st, put the new rad in last. With the old rad out of the way, u can instal the other stuff blindfolded. LOL

1000rrstunna

Pretty much got everything off/un done.... Except that push connect trans fitting grrrrrr. Any tips lol hittin you tube now

1000rrstunna

Well a good friend and master level mechanic came by with his snap on pressure tester we did each cylinder removing plugs one at a time and ensuring the piston was at tdc and holding it locked with a 1/2" breaker bar so the air pressure didn't turn her over... Readings were as follows

Cy1 13% loss
Cy2 21 % loss
Cy3 24 % loss
Cy4 12% loss
Cy5 12% loss
Cy6 13% loss

He said to put the new cooling system on and see what happens Since two cyl's side by side are at a higher % he says it may indicate a head issue... But he said my radiator looks horrible and that could definitely be the issue. Going to the store to grab the line disconnect tool and I'll put her all back together and see where we are at... What are your opinions guys what is considered a average % loss with these motors at 110k miles?
I 100% trust his opinion since he was a top fuel crew chief for a Nhra team for 10 years and has built some of the fastest local race cars.
Opinions appreciated if they have factual reasoning or logic...

Thanks again

djb383

A cylinder "leak down" test will tell u where the leak, if any, is.

1000rrstunna

I'm assuming that the correct name is a leak down test... We pressurized each cylinder and the device measures how much air blows by..

djb383

Did pressurizing the cylinders tell u what is leaking?.......rings, valves, gasket? Google "cylinder leak down test". The test will tell u where the leak is....as in rings, valves, gasket.

Radi

Don't really like to see loss number over 20%, but this is a 23 year old motor and it's going to have some wear.
I also agree that two adjacent cylinders with high loss numbers are worth keeping an eye on, that does point towards a gasket issue.
For now I'd fix up the cooling system, see how it runs and keep a close eye on your coolant levels.
If you find you are losing coolant you have a pretty good clue where to look.

That is a nice, clean '91!

1000rrstunna

This is how the rad looked on both sides over 20% gone and original lol this can't be helping...

I'm gonna have it running tomorrow I'll keep hall posted thanks so far!!

Turbo X_J

"Cy1 13% loss
Cy2 21 % loss
Cy3 24 % loss
Cy4 12% loss
Cy5 12% loss
Cy6 13% loss"

So where did it go?

1000rrstunna

Didn't listen to the exit path of the air... And the motor was cold since I couldn't start it due to the cooling system being off... Good news though I buttoned up the complete cooling system swap today and it's running great so far let it warm up burped it topped off coolant checked for flow let it warm up topped off reservoir and viola no overheat :-) it runs 200-210 all day without the heat on and my raytek probe is giving me accurate readings of 195 on the Tstat and head opposite of exhaust manifold... There was 1-2 inches if sludge in the overflow tank!!! I'm gonna flush the system out next week again to clear any leftover particulate that was in the motor or heater core. Looking good though guessing that was the overheat issue... So far I have 1097$ into the truck and it's strong!