serious overheating problem
 

hi iam having a problem with a 69 firebird 350 i just purchased. when i got the car 2 freeze plugs where out of the block. installed new plugs and filled with water. motor overheated within 10 minutes and blew out overflow. removed water pump and found upper port from timing cover to intake was clooged shut with rust. cleared hole installed new divider plate gaskets in sleeves,adjusted divider plate and replaced water pump. flushed motor with water in one sleeve of the timing cover and it came out the other one. took out radiator and flushed with water several times also used a radiator flush. still over heats. temp goes up to 230-250 and water shoots out overflow. ok heres my question what would be my next step. water is definatly flowing to radiator and t-stat is out. where else in the motor could most likely be clogged or should i buy a new radiator ist? anyone ever have this type of problem before ? thanks for any help jeff

if clogged shut with rust, you should assume rest of passages in block also clogged, water into one sleeve and out the other does not mean the block is clean, only means water crossed over from one side to the other, which could be done at the front of the block only. get radiator flush kit that ties in at the heater hoses, connect to water hose and see if water strongly comes out the top radiator hose with the hose off at the radiator end. Let us know what you found then.

How does your oil look?After completing what engineer has suggested,do a compression check and alleviate possible blown head gasket.

ok thanks engineer i will try that. i did send water thru the heater hose into fittting in head but the lower hose was off the timing cover and water came out there when i did it. i will try it again and see if it comes out the top radiator hose. jeff

68 wardog . motor was rebuilt in 99 and doesnt have a lot of time on it. the oil looks clean and the level has not changed. thanks

Why were the freeze plugs out? Did it freeze?

Freeze plugs are NOT intended to protect the block from cracking when it freezes, they're actually core plugs that seal the holes that let sand come out after the block is cast. If the block froze I think it's likely cracked (and/or the heads too).

if the block or heads where cracked wouldnt i have water in oil or be losing water out the exhaust. oil looks good and water does not leak and level does not drop when filled up. and yes i would assume that it had straight water in it and it froze and popped out 2 freeze plugs. thanks jeff

That what happens when u get a cracked block or a cracked head, as engine heats up the crack opens and puts combustion pressure into the cooling system and pushes coolant out of the rad, Not alway do u get coolant in oil as u suspect. If plugs were pushed out I would suspect u have a crack somewhere, combustion gas test should be preformed on cooling system. Won't tell u where crack is but will tell u if u have combustion gas in cooling system, ie crack or blown head gasket. Bad news.:(

how do you perform a combustion gas test??

found a prodedure in a manuel thanks. on the optimistic side could it just be a head gasket??? and would it be noticeable by looking at it if the heads where removed??

Jeff,
The motor was rebuilt in 99' but has it sat for a long period of time? Outdoors?
Did you try turning the crank manually to see if the motor is tight?
Also check the belts to make sure they are not slipping.
Also check the timing, could cause you to overheat.
Basically check the obvious before you crack into the motor.
The obvious is often overlooked and is often the problem.

I'd start with simpler items first. Last year I purchased a 72 Cutlass with a 350 and similar problem. It would go to 250-260 degrees and overflow if driven more than 10 or 15 minutes.

Found bad vacuum advance, sticking mechanical advance, leaking radiator cap and a partially plugged radiator. In addition, it had a cheap fan clutch. After replacing those items, and properly adjusting the timing, it runs 180-190 in South Florida.

ant
motor was rebuilt in 99 and i think car was on the road until 2001.then it was parked and sold to the guy i bought it from about 6months ago. dont know how long the motor was sitting with the freeze plugs popped. went thru most of the basics already. cap rotor points . timing is at about 9degrees. not sure how to check the vaccum advance i just checked intial timing.

david
i have not verifyed vacuum advance is good and it is still possible that radiator is partially clogged but i have flushed the heck out of it and i can see water shooting out the cores when i look down in the tank. running a stock 4 blade fan .

one thing i should add is that the carb is not right. it seems to have a hesitation when car goes in gear and wants to stall. dont know if this is related or just a problem in carb. took it apart once already and found dirt in the jets. does better but still not right. jeff

The fuel is probably tarnished and bad. You should consider dropping the tank and flushing it and the lines out, then have the carb rebuilt, change the fuel filter and go.

radiator
 

I recently had identical symptoms on my '75 Jeep.
The problem was the radiator. The small horizontal fins had rusted and pulled away from the verticle flow tubes. You really couldn't see it that well.
I installed a new radiator that had 50% more tubes. The temps dropped from 230-240 to 180.
In an effort to run cool, I had dipped the block, made sure the blocked flowed good. Had the radiator "cored". Installed a fixed fan, no clutch, added an oil cooler.
All the time, the radiator was just old.

dan that would be great if that is all it is. i think the easy thing to do would be to try another radiator ist. thanks for the reply. if that doesnt work i will move on the some of the other suggestions.

over heating
 

Jeff,

I hope that is all it is. When I bought my 70 Goat, it had similar symptoms of your car and we discovered a head gasket leak when we tore down the motor.

Hopefully for you, it is just a cooling problem and the block is not compromised.

Good Luck!!!

Dan

ok update on problem.intial timing set at 10. changed radiator with a new 3 core. hooked up fitting to upper radiator hose and blew air back thru engine and out lower hose and also out heater hose nipple on head. flushed block again. problem seems to be better.now motor will run a lot longer .motor stays around 180-190 but then after a little while still creaps up to about 210. does not blow out the overflow but is still running a little hot. someone had mentioned that vacuuum advance can cause motor to overheat. can someone explain to me how the vaccum advance comes into play at a idle. when i rev up the motor and look in the little window of the distributer i dont see any movement on the plate the points are mounted on? also carb still has a big stumble just off idle? still using the thermal vacuum switch. which has 2 lines on it . one to vaccum advance,1 to back of carb at vaccum tee,one to front of carb. does it matter how the lines are attached to the switch.? . as far as something being cracked i pressure tested the motor thru the hoses with 100psi and it seemed to hold pressure also compression test was 135-140 per cyl. thanks for any help jeff

Hi Jeff

I had the same problem you are describing. I found that the four blade fan and the large water pump pulley at idle slow down , where the water pump flow and air flow is to low at idle. I changed the crank pulley and the water pump pulley and the 4 blade fan to a/c pulleys and either a clutch fan or I installed a flex fan. I also run a 160 stat in it and at 100 out it will idle at 190 and runs around 170 - 180 cruising for ever and it is a 463 that runs 11.40s hope this helps.

Dan

Good article in the Dec issue of PHR magazine about the benefits of vac adv for idle. It's on page 81.

dan
thanks i will consider doing that if i cant get the problem corrected. for now i would like to try to stay with the original set-up but maybe i will try a clutch fan to see if it changes anything.

geoff
what is phr magazine. i get pontiac high performance? thanks jeff