Alright everybody. I’ve tried everything that doesn’t involve spending big money. I crank the car (‘74 Duster 225), idle it to nearly operating temps before driving, and coolant boils past the seal of the cap. When cruising at 55 for extended periods of time, the temp exceeds its normal rate. I’ve, in the past, changed hoses, thermostats, added a radiator treatment, and I am now curious to see if a new water pump will alleviate the issue. I’ve bent the cap so it can hold a tighter grip, but not beyond its capability. I’m stumped. Any tips?
What in the world is going on with my coolant?
- Thread starter zmarty27
- Start date
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67Dart273
Well-Known Member
Some basics--in no real order---
1...Have you changed the stat with a NAME BRAND stat?
2....Have you determined if the rad is plugged?
3....OldManMopar has posted that some radiators, over the years, can thermal cycle and break the fins loose from the tubes--making heat exchange null. I am convinced that happened to mine
4...DOES THE heater put out good hot air? This will give you some idea if the pump is "pumping." Also feel the hoses
5...Consider testing (chemical test) for head gasket leak, AND try leaving the cap off, see if it bubbles badly and also watch to see if it is pumping / circulating after the stat opens.
6...If possible find an infra red thermometer which can show up cold/ hot spots in the rad/ etc
7...Wind engine up, hold RPM, and watch to see if bottom hose sucks shut. This can indicate a restriction
8...Does it overheat only on the highway, or at low speed as well?
1...Have you changed the stat with a NAME BRAND stat?
2....Have you determined if the rad is plugged?
3....OldManMopar has posted that some radiators, over the years, can thermal cycle and break the fins loose from the tubes--making heat exchange null. I am convinced that happened to mine
4...DOES THE heater put out good hot air? This will give you some idea if the pump is "pumping." Also feel the hoses
5...Consider testing (chemical test) for head gasket leak, AND try leaving the cap off, see if it bubbles badly and also watch to see if it is pumping / circulating after the stat opens.
6...If possible find an infra red thermometer which can show up cold/ hot spots in the rad/ etc
7...Wind engine up, hold RPM, and watch to see if bottom hose sucks shut. This can indicate a restriction
8...Does it overheat only on the highway, or at low speed as well?
Demonic
Well-Known Member
You radiator is scaled up maybe. Take it out, get a couple gallons of vinegar - bottom shelf at the grocery store - fill it up and let it sit for 3-4 days. Rinse in reverse - bottom to top.
Go to the local lend a tool parts house and pressure check the system. If there is no coolant going out the over flow, which to leak out cap that way almost has to be, I’m leaning towards the fill neck being cracked or loose going in to tank. The bubbles around the base of fill neck would have me looking hard at that area. Yes the radiator may be scaled up and can’t hurt to clean out but the bubbles are very wrong to me. If the system can’t pressurize it will not operate properly.
67Dart273
Well-Known Member
Could be wrong cap
royslead
Well-Known Member
The cap itself, doesn't look new, check the sealing surface, and for the above; but I think I would start with a good cap.
Test the cap. If you can't, replace it with a new one. A bad cap can cause overheating problems usually after you shut it off. (it looses pressure)
Get a tester for both the radiator and the cap.... you need to know what pressure you are actually blowing at. And look carefully for damage to both the cap and the radiator top. Does the car have an overflow bottle? Or just tube to the ground??
Solder joint around rad is cracked or bung itself is cracked. Should be finding its way out the hose if anything.
You can test the cap VERY simply without spending money or doing anything other than squeezing the upper radiator hose. If you can hear air coming out of the overflow hose when you squeeze the upper hose, the cap is bad. It helps for the radiator to be full when you do it.
Inertia
Well-Known Member
If your car doesn't have a coolant recovery tank, and just the overflow tube, the coolant level should be an inch or so below full when cold.
When coolant warms, it will expand, and puke the excess out till it reaches the proper level .
When coolant warms, it will expand, and puke the excess out till it reaches the proper level .
pishta
I know I'm right....
we had a 63 300 that had a 383 w/bad head gasket. Pressurized the rad and blew it all out over time. Just filled it every 30 minutes with 4 gallon jugs in the trunk. probably should have just put the overflow into an empty jug and recycled it back in!
Blown Head Gasket
Compression from the cylinder Is trying to push the coolant back out of the radiator .
Compression from the cylinder Is trying to push the coolant back out of the radiator .
Phreakish
Well-Known Member
A pressure tester, which can often be rented for free, will test the cap and the rad. It will rule out the cap and/or head gasket.
I had a buddy who had a similar issue, so he clamped the cap tabs super tight. The next day, it blew the neck off the radiator. Turns out he had a crack in the head.
I had a buddy who had a similar issue, so he clamped the cap tabs super tight. The next day, it blew the neck off the radiator. Turns out he had a crack in the head.
Be careful thinking it's a blown head gasket. A stopped up radiator can have the exact same symptom and start it as soon as the thermostat is open. If the radiator is stopped up, when the thermostat opens, coolant coming of the engine has nowhere to go and will push its way out anywhere it can. That's what Vixen was doing when I first got her. After a new radiator she was good as new. I would begin by ruling out the simple, cheap things first.
This right here ^^^^^
Do some actual real diagnostic work and find out before you just throw parts at something based on an internet forum.
Does your oil look milky ?
Any coolant coming out the tailpipe ?
Any coolant coming out the tailpipe ?
There are a ton of good replies and I appreciate all of them. To my knowledge, the cap is original to the car. Oil looks normal and the head gasket was recently replaced. The water pump has always looked a bit crusty, but the gasket is still holding strong. Only a passing thought, though. I never gave the pump serious consideration until now. Shade tree mechanic in training, here. Getting a pressure test may be my first try; putt putting around town is still safe and practical so I may just run by the radiator shop and see if they can check it out. My next step may be taking it out, replacing the water pump (again, it’s looking rough from the exterior) and flushing it with vinegar. I’ve heard from some friends that may be worth a shot. From there, if there’s no luck, I may double check the head gasket. If that is no use, I’ll see about upgrading the rad and perhaps repairing the old. What do we think?
Phreakish
Well-Known Member
Flushing with chemicals is a last resort IMO.
Make a stop at an auto parts store and buy or borrow (you pay, then get a refund when you return it - but they give you a "house" one) a pressure tester. Takes 5 mins or less. No need to drive the car anywhere, unless risking a tow is somehow fun?
The tester comes with adapters. You can Secure it to the radiator opening, and pressurize the system. If it holds, you're fine. Next test the cap: same story. If either fails to hold pressure, then you can move to the next step. I'd replace the cap either way.
If, and only if your rad fails to hold pressure, you can look or listen for where water is dripping or gurgling to help figure out what needs fixed.
Col_Steve
Well-Known Member
If the leak doesn't start until the thermostat opens you have a plugged radiator core, not a blown head gasket, and not a cracked head. Scale from the engine block over the years gets caught in the tops of the tubes. The water pump is trying to force water down through the radiator faster than it can get past all the blockages which raises the fluid pressure on the top tank via hydraulics. Normal system pressurization is caused by fluid expansion due to heat which is regulated by the thermostat. Take the rad to a shop and have the core rodded out. He will resolder the neck while he is at it. Replace the cap with a new one when you reinstall it.
Steve
Steve
Here's what you do...and I've already made mention of it. Get the car running and up to temp. Make sure the thermostat is open. Leave the cap OFF. Easy to tell when the upper hose gets hot and the coolant in the upper tank is hot. Now cut the car off. Carefully fill the radiator SLAM full all the way to the top of the neck. Now take the top hose and squeeze it. You might need gloves or a rag if it's hot. When you squeeze it, look around the radiator neck where it solders to the top tank for bubbles. Also, remove the over flow hose from the radiator neck and see of any coolant squirts out there. If it does, put a new cap on it, you just diagnosed it without spending a dime.
I had a very Similar problem in a 62 SS Impala. The fins right in side the rad cap opening looked "ok" but further down it was clogged with deposits. I took it to be reamed out, but it was too far gone.
RRR, I'll give this a shot first. I'll be completely transparent; my confidence with troubleshooting is still elementary at best. Taking the leap, though, is part of the game, though. I'll be sure to let you all know how it goes!
It's a redneck approach, I admit, but it works and is FREE. lol
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