Overheating problem has me stumped. (1 Viewer)

Joined
Jan 10, 2017
Messages
2
Location
Oxnard CA
I have a 94 with about 280,000 miles, which i bought used a few years ago, and have been having cooling system problems ever since.

first issue was just making a noise like a coffee percolator from the expansion bottle after parking, complete with steam and some coolant coming out the overflow. Then the bottom tank of the radiator blew off. Had a shop reseal the tank, got a new cap, filled the system, forgot to put the clamp on the tiny radiator hose, got hot, but used some wire to clamp it and refilled the system.

drove fine for a while after that, but then started to have the current problem, where the heater would stop flowing, and the temperature would start to climb. Pulling over and holding the idle high would bring the temperature down, and once it got back to normal the heater would start flowing again.

I thought that it might be a head gasket leak, so I ran a combustion leak test, with the detector fluid. The fluid didn’t change color at all as the engine warmed up, and didn’t change while it was hot, and then the coolant got into the tester. During the test the heater hose never got warm, despite being set to full hot, and the two upper rad hoses made the thumping sounds of air traveling with the fluid, and plenty of air was pushed through the tester.


I’ve started to suspect a small leak is letting air into my system, so I’m planning on bypassing the heater system by running a hose from where the PHH is to the return fitting by the pump, to see if that makes any difference, but if that doesn’t work I’ll be out of ideas. Any pointers?
 

Irish Reiver

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Oct 24, 2015
Messages
1,462
Location
Orlando, Florida
4 things i would recommend and 3 have already been suggested by @vegasfj40. The third is back flush. Have you ever done one and i mean properly?
1) Theromosat
2) Fan Clutch
3) Radiator
4) Back flush

Do this and your cooling should be perfect. If you're not loosing coolant then you don't have a leak.
 
Joined
May 26, 2008
Messages
199
Location
Calgary
 
 
Head gasket or cracked head. Had similar symptoms with a 1HD-T, cracked between the intake and exhaust valves in a couple cylinders. That's a known problem on the diesel anyway.
 
Joined
Mar 9, 2016
Messages
147
Location
Napa County California
My experience with other Toyotas I’ve owned in the past is I needed a new Radiator.
Even though every mechanic and their brother will say it is a head block issue.
That’s always the first assumption.
No one just wants to go get a new radiator.
But check your thermostat first. Put a new one in.
 
Joined
Feb 7, 2017
Messages
151
Location
Tennessee
I second what @toy_tek said. I think it's a simple matter of a massive air pocket. I think if it were a headgasket issue, you would have overheating regardless of highway driving or pulling over and revving. And you would eventually pop a radiator cap. Thermostat can cause the overheating too, but I'd lean towards an air pocket myself.
 
Joined
Apr 5, 2006
Messages
785
Location
Canyon Lake, TX
 
 
First I would want to know it is full of coolant. Fill up the radiator as much as possible, Fill up the overflow bottle to the line. Drive it so that it gets to temp. Then park it. Check the levels when it is cooled all the way down again. If no change in either of the two places you filled, then it should be full. Even when an air bubble is trapped, the heatup and cool down cycle will slowly work the bubble out. The change in fluid levels under the radiator cap and overflow bottles will change as the air moves out.

Did they rod your radiator when they repaired the lower tank? I sure hope they did. They should of been able to tell you right then if it was clogged up.

Never heard of air getting sucked into the system IF the cap and overflow bottle are working correctly. Certainly not in the amount you are describing without also leaking out when it comes up to temp/pressure
 

LINUS

Waiting for the Great Pumpkin
Joined
Mar 29, 2003
Messages
5,562
Location
PNW - WA
 
 
 
Do you see/smell any hydrocarbon in the overflow bottle?

Do you have grey-ish sediment in the bottom of the bottle?


If not, try & spin the fan clutch on a cold motor - it should be resistant to spinning & only move as far as you push it.

If it spins freely at all, it’s toast.

If you’re still percolating/verified fan clutchopen the heater valve, and set the RR heater fan to blow a little - fill the whole system, maybe even put the FR end on ramps to make sure you fill the whole system.

Make sure the heater is good / not plugged & blows tons of hot air, and verify the RR heater is pushing warm air too - that’ll prove no plugging in the system.
 
Joined
May 26, 2005
Messages
7,799
Location
Phoenix
 
 
 
Easy gents, this guy posted once, two weeks ago. He either figured it out or isn't interested.
 

LINUS

Waiting for the Great Pumpkin
Joined
Mar 29, 2003
Messages
5,562
Location
PNW - WA
 
 
 
Easy gents, this guy posted once, two weeks ago. He either figured it out or isn't interested.
Haha, the yolk is on us then - he was here the 8th, I look at join dates but didn’t realize his 1st post.

Good point. :cookie:
 
Joined
Feb 7, 2017
Messages
151
Location
Tennessee
Shows how willing we are to help...poor guy posted 2 weeks ago....haha. Either that or it shows how bored we all are😋
 
Joined
Jan 10, 2017
Messages
2
Location
Oxnard CA
Hey guys, I do appreciate all the info, and will probably try those things, but I haven’t had time to work on it in a while. a few weeks after my last post, I went on a two week vacation to Yellowstone. Then, i spent a week pulling the knocking 455 in my 73 GMC motorhome (it’s a toronado FWD drivetrain, and it’s gotta come up through the floor, after you pull all the accessories off).

Now I’m taking 15 units of classes (calc 2, physics & chemistry) after having not been to school in 6 years, training to upgrade my Class B CDL to an A, helping my sister with the repair/remodel on her house, and a few other minor projects besides.

and my LC has new symptoms, too. After bypassing the heater system, and getting the air out of the heater hose loop, I burped the system and did a shakedown drive, which included some moderate trail time, and some highway time.

It did great. Temperature gauge never went over the 1/2 mark, and I dared to hope. I had noticed a misfire right before the shakedown cruise, when leaving the gas station, but it had gone away after only about a minute, and I chalked it up to lingering effects of old fuel on the fuel injectors, so I was feeling good.

I should mention that it hadn’t been driven more than a few hundred feet, total, over the previous three or four years. I had been very busy with work, and I have another car, so it got put on the back burner.

Well, after that great result, I took it to the smog shop. It drove well to the shop, but earned a Gross Polluter rating on its idle HC numbers.

The next drive the misfire was noticeable again, along with great big clouds of steam out the tailpipe. Every start since has had misfires, becoming most noticeable when the engine begins to warm up, and the one where I left the radiator cap off from cold resulted in a fountain.

I think it really is the HG.
 
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