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1969SSCamaro · 10-15-2017, 10:50 PM

I have a 1995 Georgie Boy with 454 TBI with a coolant leak that I cannot find.

Several weeks ago I had an overheating issue during a steep/long climb in 100 degree weather; temp completely ran away and had to pull-over for about an hour and wait for it to cool down so I could add more water/anti-freeze. The trip was only about 90 miles and I made it home without any issues.For the past year I had been checking the level of the overflow reservoir and never noticed a change in the level, but I suspected a leak had caused the overheating problem. I used a pressure tester to apply 15psi and discovered lower radiator hose was leaking.I Purchased T-bolt clamp as normal clamp would not seal.Did another pressure test and lower hose still leaking.Tightened clamp some more (with a ratchet) and that seemed to fix the issue after another overnight pressure test. Every time I've done an overnight 15psi pressure test it generally seems to only drop 2-4 psi.
Went for another test drive in 95 degree weather today and pushed the temp close to red line. I found it strange that the overflow reservoir did not take on any fluid at all considering how hot the temp was.Total driving time was only about 1 hour.After the engine cooled I checked radiator fluid level and it was about 8 oz low.I think there is still a leak somewhere, but I have checked all potential locations for leaks: block, freeze plugs, heads, intake, water pump, hoses, Etc.There are no obvious puddles of fluid.
I’m now suspecting an internal leak from the intake manifold or head?? I’m running another overnight test.I plan to pull the plugs as I understand a cylinder or manifold leak could result in chalky white residue on the plugs.I also ordered a new radiator cap, but mine appears to be okay: vacuum valve and 15psi pressure valve seem to normal?Any ideas on how to further isolate the leak?I am running out of ideas……….
Thanks,

LETMGROW · 10-16-2017, 04:18 AM

For those really tough to find leaks we add a coolant tracer dye to the coolant and have the owner drive the vehicle a few days. Then we have the vehicle brought back in and we look for the leak with an Ultra Violet light.
Is the engine oil level staying the same or is the level slowly getting higher indicating a leak allowing coolant to get into the oil?
Lynn

Lifemember · 10-16-2017, 04:51 AM

Is your fan clutch working? You could be over heating until the fluid boils. A 50 percent ethylene glycol and 50 percent water. This mixture has a boiling point of 223 degrees Fahrenheit. If you are hitting the red line you are well over the boiling point. Once I changed out the fan clutch, temps went back to normal, I stopped over heating and no longer lost any fluid.

Dan,

Soppy · 10-16-2017, 06:55 AM

Could be your water pump . I had the same problem , only took me 4 months to find and that was after the leak got real bad. The pump would only leak when the engine was first started ,before it reached operating temperature. The antifreeze would run down the lower rad hose and drip into the shroud. Would only loose about 1/2 a quart on a trip. Finally found it by starting the engine , the getting underneath with a flashlight and looking at the water pump.
Now I just have to get a new pump and get it changed. Not looking forward to that job. Might just wait till spring.
Never had an overheating issue.

1969SSCamaro · 10-16-2017, 08:23 AM

I have checked the water pump closely with a flashlight and have never seen any signs of coolant leaking where hoses connect, mounting junctions or weep hole, but that sure doesn't mean its' not leaking. Under normal operating conditions, once the motor reaches operating temperature, isn't it normal for the cooling system to exceed 15psi and push some of the coolant to the overflow reservoir? This seems really strange, especially since I was well above 210 degrees.

The fan clutch seems to be working (I can hear the occasional roar), but I was thinking about installing a lower temperature clutch; assuming I can find one?

It seems to run a little too hot and I'm assuming that's because I have a leak and the system is not under pressure as it should be?

I just checked the pressure test I started last night and the pressure dropped from 15 to 9psi, but that could just be the pressure tester I rented at Autozone? I did not see an puddles, but I didn't crawl underneath to check closely with a flashlight. I pumped it back up to 15 psi and will check it closely this evening after 24hrs.

On a side note; I just had new Thorley headers installed (exhaust leak on OEM manifold) and the mechanic had to increase the diameter of one bolt hole (broken stud). Are there any water jackets near the exhaust ports on the heads? I will look closely to figure out which bolt it was.

Thanks for all the responses; this is getting frustrating to isolate!

Soppy · 10-16-2017, 10:43 AM

Could also be your thermostat or temperature sender. You could use an IR temperature gun to check the actual engine temp. If the rad is full when cold , pressure should start to build up as soon as the coolant starts warming up.

Lifemember · 10-16-2017, 10:43 AM

Quote:

Originally Posted by 1969SSCamaro

I have checked the water pump closely with a flashlight and have never seen any signs of coolant leaking where hoses connect, mounting junctions or weep hole, but that sure doesn't mean its' not leaking. Under normal operating conditions, once the motor reaches operating temperature, isn't it normal for the cooling system to exceed 15psi and push some of the coolant to the overflow reservoir? This seems really strange, especially since I was well above 210 degrees.

The fan clutch seems to be working (I can hear the occasional roar), but I was thinking about installing a lower temperature clutch; assuming I can find one?

It seems to run a little too hot and I'm assuming that's because I have a leak and the system is not under pressure as it should be?

I just checked the pressure test I started last night and the pressure dropped from 15 to 9psi, but that could just be the pressure tester I rented at Autozone? I did not see an puddles, but I didn't crawl underneath to check closely with a flashlight. I pumped it back up to 15 psi and will check it closely this evening after 24hrs.

On a side note; I just had new Thorley headers installed (exhaust leak on OEM manifold) and the mechanic had to increase the diameter of one bolt hole (broken stud). Are there any water jackets near the exhaust ports on the heads? I will look closely to figure out which bolt it was.

Thanks for all the responses; this is getting frustrating to isolate!

I thought my fan clutch was working also, I did all the test on it. Had the occasional roar. So I flushed out the radiator, put all new hoses on, changed out the thermostat, waited to hear the roar of the fan clutch at start up. Then on trips I notice sometimes my fan clutch worked fine and sometimes it did not. The more trips I took the less it was working properly. Now the fan kicks in every time I near 200 and drops it to 190 and kicks off.

If your temp is that high the clutch fan should be engaged until it cools down. This would be a constant roar as your temp climbs to the read zone.

The only other suggestion I know of is a leak in the head gasket. This shows up as steam in exhaust at startup and will have a sweat smell to the exhaust.

M&EM · 10-16-2017, 11:22 AM

You may have FAN SHROUD issues that basically prevents the fan clutch from being able to do its job!

Air paths to the fan and clutch other than thru the radiator will trick the the clutch thermal sensor into seeing a lower temperature then the air actual passing thru the radiator fins. The shroud needs to seal around all 4 sides of the engine side of the radiator fin area. Some shrouds consist of top and bottom parts. Some may have additional side parts to help for a better seal around the radiator core fins.

Check for gaps around the top bottom and sides of the shroud parts for spaces where cooler air flow may sneak into the air stream coming thru the radiator fins!

1969SSCamaro · 10-16-2017, 03:52 PM

Thanks for all the information! I may just install a new fan clutch and water pump. 22 year old MH with 39K miles, it's gonna fail sometime; I'd rather replace it on my terms? I found a AC Delco Fan clutch on line, but searching for a GM. I do have full shroud coverage., but will make sure there aren't any big gaps. I'll let ya'll know what I find this evening from the latest pressure test.

Lifemember · 10-16-2017, 04:09 PM

I didn't change the water pump the shaft had no play in it. I installed the fan clutch from the top. took me a little over an hour to achieve this. I also have 39K on the MH and hope I never have to change the water pump in the near future. Being disabled takes me a little longer messing with this stuff. Good luck in your endeavor to solve the issue.

Bob_C · 10-16-2017, 04:13 PM

With the rad pressured up, and spark plugs out, spin the motor over and watch for a mist, or stream......easy way to check head gaskets ....they also make a combustion checker that work off the rad fill neck.....has a fluid that will change color if combustion present

kennyrodgers · 10-16-2017, 04:15 PM

Hi,
Sorry I can't help with the leak but I did just fit a Hayden 2797 severe duty fan clutch to our 94 TBI. It roars a fair amount and cycles more than the OEM but does a great job of keeping the temps in check. I got it from Rock Auto
More Information for HAYDEN 2797

The water pump failed on ours but you could hear that the bearing had gone south. I'd certainly go for a new T'Stat and also check the relief hose in the T'Stat housing. Ours was weeping from there and I had a hell of a job finding it.....to be honest I got lucky noticing it as I was under the doghouse doing another job at the time.

Also, whilst I think about it. I'm pretty sure your electric fan should have also kicked in at some point ? If it didn't I'd be investigating that also.
Best of luck with it.

Bob_C · 10-16-2017, 04:20 PM

You can also watch a clutch fan work by using white chalk, or soapstone, on engine side of one fan blade using a timing light.....

George Schweikle · 10-16-2017, 06:22 PM

For a long shot, check the intake manifold gasket. Our 1999 454 Vortec seemed to use coolant and a drag racing friend said the gasket is usually the culprit for this on Chevy big block engines. I did see some small seepage around the front of the intake manifold, but apparently a lot boiled off. Intake gasket manifold isn't cheap if done by a commercial shop, but I decided to have this done as the repair was outside of my skill level.