I have a leak and can't figure out where it is leaking ? My mechanic recently replaced my intake manifold gaskets and that revealed a small leak because the douche bag who had done it in the past never put sealant around the holes where coolant passes through the manifold. Anyway coolant was in my oil as the level showed when checking the dip stick. That cost me over $500. After 2 days low coolant light on again and flickers and stays on at a stop light. Burping the system is not the issue. I have more experience than most on burping my coolant system of air pockets. New parts include radiator, all hoses, radiator cap, intake manifold gaskets, throttle body gaskets, thermostat, and thermostat gasket. Is it possible I am leaking coolant through my heater ? I turned on the heater full blast and drove it for 10+ miles after adding alumi-seal. I noticed my heater wasn't blowing HOT air ? I live in Mesa AZ and it was 112 degrees that day yet my heater wasn't killing as I thought for sure the drive was going to be miserable. I am at a loss here. I am adding a half quart or more of water after 50-60 miles. It runs 190-200 degrees until I stop and it climbs to 250+ degree's. I believe this is due to the coolant level having dropped after driving for awhile. I really want to enjoy my car and this has me thinking sell this night mare and lose $5,000+ I have spent on repairs and minor interior work.

 

GOT some realll bad news......

The radiator is NOT going to stay FULL to the TOP like you want it to. So, its going to be abvout 3-4" down from the neck when normal.
That is for expansion and normal void space in the radiator.

Water is not the only thing that can cause the engine to run hotter than normal.
Take the shyrouds apart and clean. Clean out the radiator with a flush. Make sure fans are working right and spinning fast enough. Fans turn slow as they die. Trash collects behind the condensor and screws the radiator. Take it ALL apart and get it right then drive to evaluate. 230 idling on a hot day is normal. 250 after extended idle time with a/c in traffic when its 112 is NORMAL.

Its NEVER going to sit there in that ambient temps and idle in traffic at 180......

if you are loosing water then find the leak...cap, hose fitting, internal. The low sensor leaks too...if water is going inside there is evidence of that.....find it to prove it.

 

You might have the wrong radiator cap. I have heard of that causing symptoms similar to yours.

 

leesvet I don't think that driving the car for any amount of time and sitting at a red light for 3 minutes resulting in a temperature of 260+ is normal.The A/C was not on due to the fact that I hate to even see my coolant temp climb above 240 degree's.There is a leak in my car's coolant system. I need help in finding it. Where can I look other than the obvious hose connections ? I am wondering if it is possible that it is leaking via my heater ? It only leaks when the engine is running and not very fast. I can drive as far as 60 miles before it leaks to the point of causing me to overheat at a red light. I MUST FIND THIS LEAK. The radiator cap is the right one Cliff Harris. One of the first thing's I did was buy another my third cap trying to eliminate the chance it was a cheap easy solution. I am at wit's end over this leak and my inability to find it. I am 100% positive it is not internal. New intake manifold gaskets. The pressure test of both the radiator and each piston plus the fact no bubbles in my radiator and no change in my oil level indicate it is not internal.

 

I had a leak I couldn't find in my '86 very similar to yours. Turned out some previous owner had replaced the water pump and had not cleaned the old gasket off the engine very well. After the engine would heat up, coolant would drip on the floor at the front of the engine. Finally put it on a lift and found it.

 

I am going to take it over to my mechanic's today and turn it on and just let it run for 10 minutes. I should see some coolant dripping underneath the car ? Like I have said my oil level has not changed since replacing the intake manifold gaskets. Is it possible to have a internal leak of coolant without changing the oil level ?

 

If your '88 has the oil cooler option, have you checked in that area?

Are you sure the main fan is comming on and running properly?

I had a problem with my '88 IROC-Z wherein the ECM would bring on the main fan but shortly it would turn off. Changing fan relays did not cure the problem but a manual fan switch did the job.

 

No oil cooler. My fan does come on and stays steady with 200 degree's. If it hits 200 it runs and if it falls under 200 it shuts off. However my problem is a leak and the leak causes the engine to get hot once the coolant level falls under a quart and even worse when more than a quart is lost. I MUST FIND THE DAMN LEAK. I am going to go over and let it run in his drive way and I pray we see coolant while it is running. I will post what we find out. It is making me so frustrated with this car.

 

Usually if the heater core is leaking you will notice the antifreeze smell inside the car. You can also put in in defrost at the warmest and see if the window glass fogs up. If the heater core is leaking the window will fog up quickly at the desfroster vents.

Since you said you had coolant in the oil and also you are losing coolant, my guesses are that you have a gasket problem, either the intake or cylinder heads. If you are seeing coolant in the oil, or oil in the coolant those are my first two guesses. If coolant is getting to the cylinder,you may also see some white or white/blue smoke out the exhaust.

Your later post said you are sure it is not internal, so I may be way off, but those are the things I have seen before.

Good luck.

(I also lived in Mesa for about 15 years)

 

are you saying that you never see coolant under the car?

 

Okay where did I say I had coolant in my oil ? I specifically said my oil level has NOT CHANGED !!!!!!!!!!!! Is that clear now ? No coolant in my oil. I did originally and it turned out to be leaking through the intake manifold gasket. No coolant smell in the car. No coolant on the floor in my car. When I put the heat on it full blast there is no HOT air blowing in my car. I am stumped by this as well. I DO NOT KNOW WHERE the coolant is leaking ?

 

I am going over to my mechanics in a few hours[IMG]1988 C4 intake manifold leak[/IMG] I hope these images are visible ? Anyway I also hope I see coolant on the driveway but I have my doubts.

 

I hooked up a radiator pressure test. I set it at 16 same as the cap or running pressure for the car. It sat for 24hrs. End result not a drop underneath the car. The coolant must be going into the engine. This Saturday I will drain some oil into a mason jar and look for coolant. The gauge read 13 from 16. My coolant temp runs no more than 220 until it drains and gets HOT. My mechanic and I believe it is a head gasket at this point. I just paid $500 for new intake manifold gaskets. Only to have this result. Talk about ****** ! I am now faced with a choice. Rebuild, swap engines or replace the heads. I was quoted $2,300 out the door for a rebuild in Tucson. It looks to be the cheapest option. Does anyone doubt a engine rebuild at this price ? I was quoted $7,000 from a shop in Phoenix. This shop told me I need to up the injectors from the stock 24lb to 30lb if I have a different cam put in the car. I told this guy in Tucson I want 300HP. He said no other upgrade was needed besides the cam. A bigger TB or 30lb injectors was a must from the shop in PHX.

 

Slight leaks into the combustion chamber are vaporized and go out through the exhaust valve. A scan will show that it's correcting for a lean condition. You can pull the plugs and look for one that's cleaner than all the others (though it's allmost always #7) or you can get your coolant tested to see if there's any exhaust in it.

 

I was quoted $2,300 to rebuild the motor from a shop in Tucson. Is that too good to be true ?

 

Hard to say on the price; the real test is to check with some people who have had work done by that shop.

BTW, you do NOT need 30lb injectors to get 300hp at the crank. On my prior 35th Anni I simply bumped fuel pressure from 24psi to 28psi, along with some other air flow mods and achieved ~295chp.

 

I just took the motor to the shop Wed Dec 26 2012. The machine shop called me today and told they found the leak. The block has a 4 inch long crack in it. I suppose its no wonder I was leaking coolant into the motor. I swear it was a horrible leak ! I could not go more than a few miles and needed to add coolant as the sensor indicated it was low. Now I am needing a core 350. The shop owner told me he might have one for $200 since i am paying for a rebuild. I dumped $1,500 down when I dropped the piece of **** motor off. This sucks but I have no choice but to buy a 350 block. Are all Chevy 350 blocks the same provided they are iron ? Mine is a 1988 C4.