Nicole

Since we replaced the timing belt, water pump, upper radiator hose and thermostat, I have a slow coolant loss. I have never seen anything wet under the car or around the engine, but so far have added two small bottles of water.

I'm wondering, if whatever I lose evaporates - but if so, how do I best find the leak?

I have all the replacement rubber hoses in the garage, and plan to do this some time soon as a preventive measure, but I'd like to stop the current loss immediately.

ew928

You have the belly pan?
Is the bottom of the upper rad hose connections wet after driving? Wipe with white cloth/towel so you don't burn yourself.
Belly pan will catch any coolant if there's leak by water pump.
Can you see any coolant dripping anywhere after a run and with the engine running.
The hot high pressure coolant will force it's way out of any weak points whereas a cold engine won't show any leaks.

Was the cooling system all burped clean of air in the system?
You could be just filling up the cooling system if there was any air in the upper hose.
Did you guys squeeze the upper hose a few times to try and move the air out?

Mysterious fluid losses are so mentally taxing.
Think I wore out a set of hood shocks opening the hood so often to check coolant level . . .

jon928se

Check the coolant reservoir for cracks around the moulded hollow in the top of the res and for coolant in the hollow.

Coolant that leaks onto hot stuff usually leaves a white crusty residue kind of like what sea spray would look like when it drys out.

ew928

Found my cracked coolant reservoir while engine was hot and I heard hissing from the reservoir. Then I saw the bubbling from coolant on top of the reservoir.

Mike Simard

How long has it been since the work? It's normal to have the resevoir need fluid for the first day or two and if there was more air in the system to start with it may just take longer for it all to be purged by full hot-cold cycles.

TheDon007

I just went through the same scenario on my 81. I had a slow loss, which I found at the clamp fitting to the upper radiator hose. I replaced the upper, and went ahead with the lower.

After a couple of days I did not see any leaks, but I did need to top off the system when things settled in.

Do you have one of those pressure kits to test?

Mrmerlin

Nicole check to make sure the heater has been fully filled open heater control and go for a drive , check the system after it cools there is no need to BURP a 929 it has a self bleeding system ,( note the small hose to top driver side of the radiator and the small hose that comes out of the top of the water bridge)also check the rad cap it might be time to replace it, also check the right side of the radiator where the plastic end cap meets the core this is usually the most likely place to find a slow leak that leaves no drips as the coolat dries out before reaching the ground, also if you have not done this replace the small hose that connects the heater control valve to the back of the engine, and the heater control valve as well these 2 parts will eventually fail on there own, all the while looking for leaks or tell tales of a white crusty deposit on the engine or radiator,look at the connection to the heads where heater hose connects sometimes these gaskets will start leaking , there is a block off plate on the driverside rear head check this as well,(Aircleaner needs to be removed to see this area).
Look under the car along the head gasket see if the gaskets are oozing and see if the block drains are both tight, and the radiator drain(blue plug is tight but not too tight), and last but not least recheck all of the hose clamps sometimes they just need to be resnugged

Normy

Step 1: Give all your coolant clamps a GOOD tightening.

Step 2: Replace your coolant cap.

If you're still losing coolant after that, then have the system pressure tested by a shop. If there's a leak, they'll find it on the cheap.

N

928SS

could be a headgasket... I wondered where my anitfreeze was going till the motor hydrolocked.

Joe '87 S4

I had my coolant flushed last September and twice since then about a few months apart, I've gotten a "low coolant" light. I added about a 1/2 cup each time to bring it up to the line. There's no sign of a leak anywhere and I would normally be worried but since I never had a coolant warning before the flush, I'm hoping that it just wasn't filled to capacity. It's been about a month since the last top off and no light yet. Maybe you're in the same situation Nicole?

the flyin' scotsman

Remove the rad cap and pressurize the system; pump with guage.

If the leaks are not found on any of the external hoses (don't forget the little hose to the heater valve) look at the reservoir and the heater core. If still not found start looking at the engine.

Nicole

Thanks, guys!

Can anyone remind me real quick: IF there is ever a head gasket failure, would you more likely find coolant in the oil, or oil in the coolant? Can't remember, but I think it's cooland in the oil, right?

Normy

Nicole-

Our cooling system runs at 13 psi max, which means that it runs somewhere below that number.

The oil system runs at 3-5 bar, or 3-5 times atmospheric pressure. Atmosphere is 14.7 psi, so figure that your oil is between 45-75 psi. From this it is easy to conclude that the oil would be squirting into your coolant and you'd have froth in your reservoir. But life is never that simple....

As soon as the oil pump stops....so does all the bar. But the coolant continues to sit at something less than 13 psi for 45-60 minutes or so. During that time, if you have a blown head gasket, the water can now make its way into your oil system, which of course is a huge disaster. Pretty quick you have what looks like a milk shake in your oil pan, and your engine's bearings are gone within 1000 miles. I know, I've been there- this happened on a Fiat Spyder that I owned in San Juan for 9 months. The engine seized when the bearings finally failed. I knew it was dying; I didn't realize it was about to die. I wound up selling the car to a local preacher who had access to a Fiat engine, and he's still driving it 12 years later, far as I know.

N

Daniel Dudley

Very unlikely that you have a head gasket leak if you haven't overheated the engine. There are several types of leaks, and the old age failure usually results in seepage of coolant onto the top of the block or onto the exhaust manifolds. Head gasket failures where the seal to the cyliner is compromised leads to bubbles in the radiator and coolant into a cylinder. Leaks between the oil and the coolant passages can lead to coolan or oil going either way, and will often show up as a frothey, gooey deposit on the oil filler cap. A little of this is normal, so don't panic if you see a little, just wipe it out.

What Normy said is good advice. Tighten the clamps first and top off. I have had trouble with replacement water pumps, but if you have a leak, you should top the car off cold and run to temp. If you have an external leak you should get a slight whiff of radiator fluid. The best time to look for a leak is with a flashlight after dark, as the light will shine well without the sun creating contrast.

Look at the hose ends, and at the front of the engine at the bottom. This is where you would find evidence of a leaky WP or gasket. Check around the thermostat too, and under the intake manifold if you can. Since you didn't have this problem before, chances are it is related to something that was just done, so look to those things. Don't go crazy tightening, just check for looseness. It happens a lot. LOL and good wishes.

IcemanG17

Nicole
A compression check will determine if your headgasket is bad.....since you have a slow leak & can't find it.......it is possible that a slight leak around the outside of the waterpump seal...did you have to rebuild the gasket with some of that instant gasket stuff? But you'll have to take the front of the engine apart to find it.....