5.0 Over Heating Problems

roadrunner19va · Oct 6, 2006

I have a bone stock 1991 Mustang lx 5.0. I am having a weird overheating problem. When I drive the car normal the temp gauge never leaves half way. when ever I get up on it for a little bit the temp. climbs all the way up. Once it goes all the way up it will not cool down until I turn the car off for a little while. Last week I drove it 2 hours and it never left half way. I was about 40 miles from home and I punched the gas for about a minute. The temp went all the way up. I then drove it normal with the heat on for the rest of the way. and the temp stayed close to over heating. The gauge does not go into the red it gets to the last mark before red. I replaced the thermostat and it still does the same thing. Let me know if anyone could have a clue as to whats causing this. I now it is getting close to overheating because when I parked it there was antifreeze bubbling out of the overflow (Barely dripping). It only does it when I accelerate hard for a little bit. It is weird.

SVT32VDOHC · Oct 8, 2006

Wow, that is a weird one. Is the water pump in good shape? I always put a new one on the 5.0's when I get them. Do your windows fog up? IF they do that is signs of a bad heater core. Good luck man...

roadrunner19va · Oct 8, 2006

Over Heating Problems

I am thinking it is the water pump also. No my heater core is fine. I will put a water pump on it and see what happens. Thanks Travis

HISSIN50 · Oct 8, 2006

What makes you think the water pump is bad? It's a simple mechanical device.

Have you pressure tested the system? Have you replaced the cap? The pressure (~16 PSIG) in the system raises the effective boiling point approx 50*F, and it's often while at speed that a lack of pressure becomes an issue.

Random thoughts.

Good luck.

GTOreturns · Oct 8, 2006

Yeah the pumps either good or bad. Is there ANY little leaks in the system? Ive had pin hole leaks that would give me over heating problems. Also, if you have the stock H-pipe your cats could be clogging. Mine was always running hot,replaced all the hoses, got a FMS racing water pump, new radiator and was still running over 200 degree's. I took the stock h pipe off and put a catted x pipe on and woola!! Problem solved.

Nopantz · Oct 8, 2006

i had a similar weird issue it ended up my radiator had a leak in it...got a new radiator and now i have no cooling issues.

gcwh02 · Oct 8, 2006

+1 on the water pump is either good or bad. First, try replacing the radiator cap. Could be the radiator itself like said before also.

90mustangGT · Oct 8, 2006

Get a block tester and check for hydrocarbons in the radiator.

fordman54935 · Oct 9, 2006

roadrunner19va said:
I have a bone stock 1991 Mustang lx 5.0. I am having a weird overheating problem. When I drive the car normal the temp gauge never leaves half way. when ever I get up on it for a little bit the temp. climbs all the way up. Once it goes all the way up it will not cool down until I turn the car off for a little while. Last week I drove it 2 hours and it never left half way. I was about 40 miles from home and I punched the gas for about a minute. The temp went all the way up. I then drove it normal with the heat on for the rest of the way. and the temp stayed close to over heating. The gauge does not go into the red it gets to the last mark before red. I replaced the thermostat and it still does the same thing. Let me know if anyone could have a clue as to whats causing this. I now it is getting close to overheating because when I parked it there was antifreeze bubbling out of the overflow (Barely dripping). It only does it when I accelerate hard for a little bit. It is weird.

I had those same symptoms, and it ended up being a bad headgasket.

vristang · Oct 9, 2006

I'm with JT on this....

Pressure test the system.
A small leak can make the cooling system do weird things.

jason

SVT32VDOHC · Oct 9, 2006

I only said water pump because I always put a new one one every time I buy and flip a Mustang. Along with that I do hoses, fluid and T-stat. Out of the 10 Mustangs I have had, 8 of them have been 5.0L and 0 of them have had any issue with over heating. I have had stock ones, modded ones, low miles and high miles. All I did was give a suggestion. A couple of my Mustangs that I did do water pumps on had some crappy build up behind there, and a lot of the passageways looked 40-50% blocked. I never ran the cars before I replaced the pumps, but I am sure glad I spent the 27 dollars so I did not get stranded.

HISSIN50 · Oct 9, 2006

SVT32VDOHC said:
I only said water pump because I always put a new one one every time I buy and flip a Mustang. Along with that I do hoses, fluid and T-stat. Out of the 10 Mustangs I have had, 8 of them have been 5.0L and 0 of them have had any issue with over heating. I have had stock ones, modded ones, low miles and high miles. All I did was give a suggestion. A couple of my Mustangs that I did do water pumps on had some crappy build up behind there, and a lot of the passageways looked 40-50% blocked. I never ran the cars before I replaced the pumps, but I am sure glad I spent the 27 dollars so I did not get stranded.

I'm with ya bud. The WP just wasnt where I'd start necessarily. If a pump looks that bad, I'd be afraid to see what other parts of the system look like, and they'd likely need addressing too.

I like to replace the pump anytime I have it off, and it's not a bad preventative thing to do if it's not OEM (I don't think much of the parts store stuff, even when new instead of reman'd. Esp. with clutch driven fans). Anyhow, my only take was that it's good to replace but might not be the fix.

brin0357 · Oct 10, 2006

do you have a thermostat?

roadrunner19va · Oct 10, 2006

5.0 overheating

I replaced the stock thermostat with an oem replacement from advanced auto. I do not think that the system has a leak. I will have it pressure tested to see if it has any leaks. I will also check the converters. When It starts to get near the overheating mark It feels like the center console gets really warm. I never thought anything of it. How do I check the converters? I live in maryland and have to go through emissions. So gutting them would not work. How else can I check the converters? Let me know if anyone knows for sure that the converters could be the problem. Like I said the car only gets hot when I accelerate hard for a short bit. I just do not know why it will not cool back down. I might just start replacing everything until it fixes it. I hate trying to diagnos a problem like this. Plus I will know that all parts are new. Thanks for all of your help.

vristang · Oct 10, 2006

When was the last system flush?
Can you see corrosion in the rad?
What coolant mix ratio are you using?

Just some things to consider, if you haven't already.

It is obvious that the cooling system is maxed out....
The question is where is the weak link?

Just thinking out loud,

jason

HISSIN50 · Oct 10, 2006

I would not be thinking exhaust restriction for an overheating issue.

But to check it easily: you can install a vac gauge and route it to the interior. Then as you drive along at a totally constant speed, you can note if the vac reading starts to diminish in a meaningful way. This test does work but can be easier to use while driving (it works while the car is stationary but the exhaust system has to be pretty clogged).

Ive gotta ask (I'm sure someone did already, but since this thread is taking off): You do have a real temp gauge, right? Making decisions and doing diagnostics with a stock gauge is just not something you'd want to do.

Good luck.

roadrunner19va · Oct 10, 2006

5.0 Over Heating

I am using a stock gauge but It has over heated on me 3 times since I purchased it. The first time I pulled over and there was antifreeze bubbling out of the over flow pretty good. I turned the car off for 2 hours and then drove the rest of the way home and the temp never left the half way mark. So I replaced the thermostat thinking it was stuck shut. I then drove it normally for 3 hours to virginia and not one problem. Then on the way home it drove fine for 2 hours until I raced a ricer. Then it went close to overheating and stayed there for 30+ mins of driving normal. I turned the heater on and it made no difference. When I finally made it home coolant was bubbling from the overflow barely. the last two times it was just barely dripping from the overflow. I could tell by the coolant coming from the overflow that it was hot. It was steaming. I wish someone could come by and look at it and see for their self. It is weird. Almost unbelievable. If anyone lives around the DC, MD. area you are more than welcome to come look at it and help me figure it out. If it fixes it I might even pay you for the help. Thanks Travis

roadrunner19va · Oct 11, 2006

5.0 overheating problem

ttt

Prime Lord · Oct 11, 2006

First off, get yourself a real temp guage. The factory one sucks balls, and this way you'll have an idea what your really working with.

Secondly, it sounds like your radiator is gummed up. If its happening REALLY regularly, just junk it and get a NEW one.

I've found the recipie for the PERFECT 180° Mustang:
Brass 3-row radiator (from your local parts store), Police fan clutch (or GOOD electric fan), Stuart Components Stage-1 Water Pump, & a 180° Balanced Mr. Gasket Thermostat. This setup NEVER got above 182° on my digital temp guage.

SVT32VDOHC · Oct 14, 2006

HISSIN50 said:
I'm with ya bud. The WP just wasnt where I'd start necessarily. If a pump looks that bad, I'd be afraid to see what other parts of the system look like, and they'd likely need addressing too.

I like to replace the pump anytime I have it off, and it's not a bad preventative thing to do if it's not OEM (I don't think much of the parts store stuff, even when new instead of reman'd. Esp. with clutch driven fans). Anyhow, my only take was that it's good to replace but might not be the fix.

It's cool man, no problem, it's hard to understand exactly how people word stuff or come off on the internet. No hard feeling!

5.0 Over Heating Problems

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