Overheating and I don't know why
Thread Starter
Instructor
Joined: Oct 2007
Posts: 188
Likes: 3
Overheating and I don't know why
Hi, I have a 1987 L98. It is overheating in about 10 miles. The water pump is dry, the upper hose is dry, the lower hose appears dry, but the right side, out of the overflow tank pisses out about 2 gallons and then the car overheats. I leave it, it cools down, I put 1 1/2 to 2 gallons in it and it does the same thing. What is that??
- bad radiator cap?
- bad thermostat?
- Blocked hose or radiator?
- Head gasket blown?
- water pump not pumping?
It does not seem down on power, The overheating may be due to the coolant lose? I am not understanding the problem
- bad radiator cap?
- bad thermostat?
- Blocked hose or radiator?
- Head gasket blown?
- water pump not pumping?
It does not seem down on power, The overheating may be due to the coolant lose? I am not understanding the problem
Team Owner
Joined: Jul 2004
Posts: 28,475
Likes: 3,291
From: Hartford WI
Hi, I have a 1987 L98. It is overheating in about 10 miles. The water pump is dry, the upper hose is dry, the lower hose appears dry, but the right side, out of the overflow tank pisses out about 2 gallons and then the car overheats. I leave it, it cools down, I put 1 1/2 to 2 gallons in it and it does the same thing. What is that??
- bad radiator cap?
- bad thermostat?
- Blocked hose or radiator?
- Head gasket blown?
- water pump not pumping?
It does not seem down on power, The overheating may be due to the coolant lose? I am not understanding the problem
- bad radiator cap?
- bad thermostat?
- Blocked hose or radiator?
- Head gasket blown?
- water pump not pumping?
It does not seem down on power, The overheating may be due to the coolant lose? I am not understanding the problem
Instructor
Joined: Oct 2008
Posts: 193
Likes: 19
From: Stevenston, Scotland, GB
1. What do you mean by dry?
2. Empty pipes?
3. Does the fan work?
4. Does it come on at temperature? If not, the system will heat up and dump all the coolant out of the radiator cap into the header tank. If the fan is working, check the thermostat.
5. Got any high temp figures on the dash?
6. Warning lights?
7. Do all the pipes feel hot when its running?
8. Does the fan blow hot air when it should?
2. Empty pipes?
3. Does the fan work?
4. Does it come on at temperature? If not, the system will heat up and dump all the coolant out of the radiator cap into the header tank. If the fan is working, check the thermostat.
5. Got any high temp figures on the dash?
6. Warning lights?
7. Do all the pipes feel hot when its running?
8. Does the fan blow hot air when it should?
Safety Car
Joined: Aug 2009
Posts: 3,752
Likes: 276
From: Melbourne, Victoria, Australia
Hi, I have a 1987 L98. It is overheating in about 10 miles. The water pump is dry, the upper hose is dry, the lower hose appears dry, but the right side, out of the overflow tank pisses out about 2 gallons and then the car overheats. I leave it, it cools down, I put 1 1/2 to 2 gallons in it and it does the same thing. What is that??
- bad radiator cap?
- bad thermostat?
- Blocked hose or radiator?
- Head gasket blown?
- water pump not pumping?
It does not seem down on power, The overheating may be due to the coolant lose? I am not understanding the problem
- bad radiator cap?
- bad thermostat?
- Blocked hose or radiator?
- Head gasket blown?
- water pump not pumping?
It does not seem down on power, The overheating may be due to the coolant lose? I am not understanding the problem
Check your radiator cap, it should be 15 psi or 16 psi.
What temperature does the dash show does it run at normal temperature then rises as coolant is lost?
Check the space between the a/c condenser and radiator, leaves twigs all get caught up in there blocking airflow. That could result in coolant loss if it overheats.
Does the cooling fan work?
could most likely be a bad radiator cap?
From memory it should only transfer a small amount like a pint of so to the recovery tank, during normal temperature 190F-230F
The fan is controlled by ECM if you have the booster fan in front of a/c condenser and main cooling fan behind radiator.
The ECM doesn't start the cooling fan until around 230F
Over 250F i would expect more coolant venting into the recovery tank, can hear bubbling noises if it starts to boil.
This all depends on your coolant mix, i use 50% antifreeze anti boil coolant concentrate with water.
That should raise your boiling point to around 260F with a 15 psi radiator cap, if your coolant is boiling below 260F and you have a 50/50 mix your radiator cap is faulty. Pressure raises the boiling point also.
Good luck
Safety Car
Joined: Aug 2002
Posts: 3,842
Likes: 230
From: SANTA CRUZ CA
Blown head gasket.
Your description suggests exhaust gases are entering the cooling system super heating the coolant, and forcing coolant into the overflow bottle.
The cooling system and block can be pressurized to confirm a problem gasket, and there is a simple test that can detect exhaust gases in the coolant.
Your description suggests exhaust gases are entering the cooling system super heating the coolant, and forcing coolant into the overflow bottle.
The cooling system and block can be pressurized to confirm a problem gasket, and there is a simple test that can detect exhaust gases in the coolant.
Safety Car
Joined: Sep 2001
Posts: 4,157
Likes: 554
From: Glenbeulah Wi
First thing to check is the thermostat. I assume it is not opening which will not allow the coolant to circulate and it will boil and fill up the overflow tank. Fill the car with coolant and start it and let it idle, once it gets up to 195 degrees the thermostat should open and water should flow through the upper radiator hose through the radiator back through the lower hose into the pump. If you should be able to feel the flow through the hoses, if there is no flow start looking for the restriction. Thermostat failure is not uncommon so that is my first guess. Good luck!
Thread Starter
Instructor
Joined: Oct 2007
Posts: 188
Likes: 3
1. What do you mean by dry? I am not leaking out of a bad hose or a water pump bearing
2. Empty pipes? Radiator is full, hoses are not collapsed
3. Does the fan work? I will check
4. Does it come on at temperature? If not, the system will heat up and dump all the coolant out of the radiator cap into the header tank. If the fan is working, check the thermostat. I am thinking about removing the thermostat entirely as a test
5. Got any high temp figures on the dash? floats around 160-180 when dumping coolant, then straight to >230, when I shut it down. It runs at about 180 on the highway and rarely above 220 on the street. I think years ago I had the computer turn on the fans at a lower temp.
6. Warning lights? None
7. Do all the pipes feel hot when its running? Yes, and firm
8. Does the fan blow hot air when it should? what fan? The heater works and helps with cooling, the radiator fans work - I think, but I will check
2. Empty pipes? Radiator is full, hoses are not collapsed
3. Does the fan work? I will check
4. Does it come on at temperature? If not, the system will heat up and dump all the coolant out of the radiator cap into the header tank. If the fan is working, check the thermostat. I am thinking about removing the thermostat entirely as a test
5. Got any high temp figures on the dash? floats around 160-180 when dumping coolant, then straight to >230, when I shut it down. It runs at about 180 on the highway and rarely above 220 on the street. I think years ago I had the computer turn on the fans at a lower temp.
6. Warning lights? None
7. Do all the pipes feel hot when its running? Yes, and firm
8. Does the fan blow hot air when it should? what fan? The heater works and helps with cooling, the radiator fans work - I think, but I will check
Last edited by Frank-in-San-Diego; Apr 18, 2017 at 09:43 AM.
Thread Starter
Instructor
Joined: Oct 2007
Posts: 188
Likes: 3
Check your radiator cap, it should be 15 psi or 16 psi. I will buy a new one today
What temperature does the dash show.....It always ran cool, i think I switched out the stat to 180 years ago. It floats around below 180 for a time than when it loses coolant, it goes up to 230 fast. At that point I shut it down
Does the cooling fan work? I will check
could most likely be a bad radiator cap? Yep, will buy today
The fan is controlled by ECM.... I think I can jump this direct to 12V and force them to run 100 percent and check
What temperature does the dash show.....It always ran cool, i think I switched out the stat to 180 years ago. It floats around below 180 for a time than when it loses coolant, it goes up to 230 fast. At that point I shut it down
Does the cooling fan work? I will check
could most likely be a bad radiator cap? Yep, will buy today
The fan is controlled by ECM.... I think I can jump this direct to 12V and force them to run 100 percent and check
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Thread Starter
Instructor
Joined: Oct 2007
Posts: 188
Likes: 3
thermostat. Yes, in the past (5 years and 40,000 miles ago) I was having issues with air in the system. I put in the coolest thermostat - I think that was 180, and I drilled 4 small holes in the sides. It solved my air entrapment issue. I am thinking to pull the stat out entirely as a test
Team Owner
Joined: Jul 2004
Posts: 28,475
Likes: 3,291
From: Hartford WI
Safety Car
Joined: Aug 2002
Posts: 3,842
Likes: 230
From: SANTA CRUZ CA
Racer
Joined: Feb 2004
Posts: 427
Likes: 86
From: Rockwall TX
yes, run without tstat, free and easy.
if head gasket, would get a steady stream of small bubbles in reservoir, not a gallon dumped after 10 minutes.
try not to drive car like this or might really cause head gasket problem.
that chemistry test in vid is spot on, dude knows the n* is toast and knows not to even bother to try replacing that hg, likely caused by overheating.
and just for clear communication, the tank with the cap is the 'reservoir, high fill', the other tank near the headlight is 'reservoir, coolant recovery'. From which tank is the gallon dumped, reservoir tank or recovery tank?? That will answer good cap or bad cap.
if head gasket, would get a steady stream of small bubbles in reservoir, not a gallon dumped after 10 minutes.
try not to drive car like this or might really cause head gasket problem.
that chemistry test in vid is spot on, dude knows the n* is toast and knows not to even bother to try replacing that hg, likely caused by overheating.
and just for clear communication, the tank with the cap is the 'reservoir, high fill', the other tank near the headlight is 'reservoir, coolant recovery'. From which tank is the gallon dumped, reservoir tank or recovery tank?? That will answer good cap or bad cap.
Thread Starter
Instructor
Joined: Oct 2007
Posts: 188
Likes: 3
UPDATE
This is a slow moving project, but I did buy a thermostat and a radiator cap. I put the new cap on and ran the car in the garage. It heats to 220, the fans come on and then it drops to 210 and stays there - cool.
So I took a ride and it runs great until about 20 miles out. Then I had a runaway and the temperature goes up until I shut it down.
The radiator is cool (cold) until there is a run away. Thermostat stuck????
This is a slow moving project, but I did buy a thermostat and a radiator cap. I put the new cap on and ran the car in the garage. It heats to 220, the fans come on and then it drops to 210 and stays there - cool.
So I took a ride and it runs great until about 20 miles out. Then I had a runaway and the temperature goes up until I shut it down.
The radiator is cool (cold) until there is a run away. Thermostat stuck????
Team Owner
Joined: Jul 2004
Posts: 28,475
Likes: 3,291
From: Hartford WI
UPDATE
This is a slow moving project, but I did buy a thermostat and a radiator cap. I put the new cap on and ran the car in the garage. It heats to 220, the fans come on and then it drops to 210 and stays there - cool.
So I took a ride and it runs great until about 20 miles out. Then I had a runaway and the temperature goes up until I shut it down.
The radiator is cool (cold) until there is a run away. Thermostat stuck????
This is a slow moving project, but I did buy a thermostat and a radiator cap. I put the new cap on and ran the car in the garage. It heats to 220, the fans come on and then it drops to 210 and stays there - cool.
So I took a ride and it runs great until about 20 miles out. Then I had a runaway and the temperature goes up until I shut it down.
The radiator is cool (cold) until there is a run away. Thermostat stuck????
Melting Slicks
Joined: Feb 2003
Posts: 2,677
Likes: 812
From: Saskatoon Sask.
UPDATE
This is a slow moving project, but I did buy a thermostat and a radiator cap. I put the new cap on and ran the car in the garage. It heats to 220, the fans come on and then it drops to 210 and stays there - cool.
So I took a ride and it runs great until about 20 miles out. Then I had a runaway and the temperature goes up until I shut it down.
The radiator is cool (cold) until there is a run away. Thermostat stuck????
This is a slow moving project, but I did buy a thermostat and a radiator cap. I put the new cap on and ran the car in the garage. It heats to 220, the fans come on and then it drops to 210 and stays there - cool.
So I took a ride and it runs great until about 20 miles out. Then I had a runaway and the temperature goes up until I shut it down.
The radiator is cool (cold) until there is a run away. Thermostat stuck????
Team Owner
Joined: Jul 2004
Posts: 28,475
Likes: 3,291
From: Hartford WI
Safety Car
Joined: Sep 2001
Posts: 4,157
Likes: 554
From: Glenbeulah Wi
UPDATE
This is a slow moving project, but I did buy a thermostat and a radiator cap. I put the new cap on and ran the car in the garage. It heats to 220, the fans come on and then it drops to 210 and stays there - cool.
So I took a ride and it runs great until about 20 miles out. Then I had a runaway and the temperature goes up until I shut it down.
The radiator is cool (cold) until there is a run away. Thermostat stuck????
This is a slow moving project, but I did buy a thermostat and a radiator cap. I put the new cap on and ran the car in the garage. It heats to 220, the fans come on and then it drops to 210 and stays there - cool.
So I took a ride and it runs great until about 20 miles out. Then I had a runaway and the temperature goes up until I shut it down.
The radiator is cool (cold) until there is a run away. Thermostat stuck????
Team Owner
Joined: Jul 2004
Posts: 28,475
Likes: 3,291
From: Hartford WI