Coolant Loss

One of the vexing issues I've had recently with Baby Blue has been the loss of coolant. At first I thought it was through where the heater return line hits the hose, as this has always been a trouble spot. However, the coolant has still been disappearing. Hoses are new. Water pump replaced last year. No spots on the ground that I can find. My next step was to close up the spigot to the heater core. This seemed to have cured the issue, but then it happened again. It's not a major fluid loss, but every few drives, I have to put a little bit of coolant into the radiator to bring it back up to the top.

The overflow tank is always filled to the brim. In fact, when I opened it tonight some 6 hours after driving, it sent a bunch of coolant onto the ground through the overflow hose. When the radiator is opened, the antifreeze level is 3 to 4 inches down.

It sees that if nothing else is leaking, then the only other way to lose coolant is a pinhole leak in the head gasket. There's no evidence of it in the exhaust, but I'm running out of possibilities on where this coolant is going. I'm hoping that retorquing the head bolts will solve the problem, as a head gasket change would sideline the car during one of the best times of year to be driving it. Any other suggestions?

Expansion. You're overfilling it. Don't look for problems. Problems will find you. (rings gong)

:friendly_wink:

I agree that something is amiss. You should not lose coolant level in the radiator itself....just in the expansion tank. I am assuming that the expansion tank is staying full while the radiator level goes down. That would mean that when the car cools air is being drawn in somewhere. I had this problem and it turned out to be a pinhole leak in the radiator. I'm wondering if leakage around the heater valve stem could account for it. Hopefully some experts will chime in since almost all my experience is with the top tank radiator's like Steve is referring to.

Kurt

Sounds like your cap is bad, or not sealing properly on the radiator neck. Inspect the neck sealing surface. If OK, replace the cap.

I agree: if you overfill it will push out the excess. If it's a quart or so "low" that's no problem. And yes, check the cap.

If it is also overheating, be sure you don't have a thermostat that is too high. I would suggest a 180F or even a 165F (I run the lower temp one in my MGB).

Also, check the lower rad hose. That hose is under suction and sometime an older hose will "suck closed" which can cause local overheating (but you may not see it on the gauge). Squeeze the lower hose and see if it's soft. And, rev the engine and observe if that hose is sucking closed.

If no luck, do a compression test and see if you have any low cylinders (you can have a head gasket that leaks coolant without losing compression but it's pretty rare).

Folk's, I think he has the cross flow radiator and he should not be losing coolant in it while the expansion tank stays full. If things were working as they should the expansion tank should be the only place that sees a change in fluid level. The coolant in the system should be sucked back into radiator as the engine cool's. The fact that his rad level drops while the expansion tank stays full can only mean that air is getting into the system in most likely the same place coolant is leaking out. Personally, through the engine is the last place I would look but it may be the case. I would fill the system, warm up the car and start looking for any place that is wet. If that doesn't do it find a radiator pressurizing pump and try that. I believe its been mentioned that some parts store's have them for loan or a decent mechanic would have one.
When i had a problem with the cross flow it was on a car that originally had a down flow and I just changed radiator's.

Kurt.

One other thought, I had a pinhole leak in a <relatively> new hose - only ever showed up when the engine was running and, since I always turned off the engine before I looked, it took a while to diagnose. <doh>

Do you have the correct rad cap?

Have you done a coolant system pressure test? Took me 3 days with system under pressure in my Cooper to find a small drop on floor. These testers are not real expensive at the local parts store. I pumped system to the maximum specifications of 17lbs. for cap and system and waited. Took 3 days to find a spot smaller than a dime, contributed to a thermostat gasket.

How are you defining "full" on the radiator?

Lots of good advice here. Yes, it is a cross flow radiator. I'm running a 165 degree thermostat. I'm defining full as being able to see only the top row (or top two, max) of the core when I open up the actual radiator bolt. My cap does not appear to be original. It's the typical cap you see on 99% of the radiators out there. Could have the overfill been caused by me closing down the spigot to the heater core? Is there any advantage to closing up the spigot to the core?

The core isn't very pretty -- there's a fair amount of deposits surrounding the various openings. Given that most of the rest of the cooling system has been replaced (water pump, all hoses, heater core spigot, return line), the radiator could be a likely suspect. The crossover pipe at the bottom appears to be original, too.

I guess I'd have to clean off the garage floor of all the oil spots (both from the car and a few of my "oops" moments) to check for the other leaks.

Could be going out the tailpipe. Find a shop with a CO sniffer.
Bob

SaxMan said:

My cap does not appear to be original. It's the typical cap you see on 99% of the radiators out there. Could have the overfill been caused by me closing down the spigot to the heater core?

Click to expand...

this could be a clue - someone help me here, don't some of Spridget rads take a longer than standard rad cap

JPSmit said:

this could be a clue - someone help me here, don't some of Spridget rads take a longer than standard rad cap

Click to expand...

The down flow rad's used a long shank rad cap, JP.

Kurt.

I was driving Baby Blue today and when I put her back in the garage, I smelled coolant. I popped the hood and looked around. Coolant was on the front crossmember directly beneath the crossover pipe. I believe all it may be is a loose hose clamp on the driver's side of the crossover pipe when I ran a paper towel around the connection, it did get wet. The only other options are the crossover pipe itself or possibly the bottom of the radiator, although I ran my hands along the bottom of the radiator and it seemed dry. I'm hoping it's just a loose clamp.

Sounds as if you are narrowing it down. Got to thinking and was wondering if you have a leak around the stem of your heater valve. Seems like where I put the blame in the past.

Kurt.

I found the offending leak this morning when my daughter and I were out for a Sunday cruise and stopped at a park. As walked back to the car, I spotted a small column of steam coming out from under the hood. The leak is on the lower left hose where the heater return line enters it. Basically, the rubber part which goes on the heater return line is separating from the main part of the hose. It's a bit frustrating as the hose is only a year old. However, I think this was caused by fitting issues when I replaced the brass return line over the winter. The one I ordered was slightly longer than the one that was in the car and that may have put too much lateral pressure on the hose. I'm thinking of going Kevlar this time...and being a bit more conscious about the fit of the return line.

I had been keeping the car relatively close to home base just in case I had to make a dash for home. We did make it home without the overheating from the loss of coolant.

I put the new hoses in tonight. I went with the Kevlar ones and there is a very noticeable difference in the quality of the hoses. Unlike when I replaced the hoses a year ago, the hoses came off and the new ones went back on with little incident. The elbow hose down at the right front is always a pain in the butt to access, but wasn't terrible.

The fun began once I refilled the coolant. I bought the radiator pressure test kit from Harbor Freight, but none of the caps were a match for the Sprite. The best I could do was one of the plunger looking ones and wrap some electrical tape around it to get a seal. I could only get about 6 to 8 psi before the seal would blow. So I tried to wedge it in a bit more with a mallet, until it popped through the other side of the recovery tank neck. The mistake I made was when I then disconnected it from the pump. Plop! It went straight to the bottom of the recovery tank. After doing some fishing to no avail, I drained the recovery tank with a siphon, used a coat hanger and fished the piece out. If there was any upside to this, I learned how utterly filthy the inside of the recovery tank was. That will be a winter project.

So far, no leaks. Tomorrow morning, I'll take the car out for a spin and see what happens once we get up to operating temperature.

...and everything was nice and dry after the test drive. No coolant leaks at all. Just in time for the extended weekend :tennis:

Woohoo!