Cooling system (Fans working, but still showing hot)

[Fluxn83]

I noticed lately, that while driving, my DMC-12 has no issues with the cooling system keeping the engine cool. However, when I'm parked or not moving (engine still running), I hear my cooling fans kick on, but my temperature gauge still rises ever so slowly while they're working. Then, when I get to moving again (not very fast, 1st or 2nd gear), the gauge drops back to the preferred temperature (about 180) within seconds. No difference when my A/C is on or off. What's going on?

[Bitsyncmaster]

Verify both fans are working. Have not heard of anyone having a fan get weak. Also I assume your alternator is working fine.

[David T]

Check a few things. As bitsyncmaster said, make sure both (2) fans are working. Make sure they are both sucking air in from the radiator and blowing out the back towards the gas tank. Make sure the fans are firmly attached to the motor shafts. Make sure there is NOTHING obstructing the inlet grill like a license plate, leaves, etc. Bleed the radiator by pressurizing the system and loosening the small hose on the top, right side to let any air out. If you still have the original rad with plastic tanks, you should replace it. Make sure the header tank is 1/2 full when the motor is cold. Make sure the coolant is nice and green, protects to -40 and is not over 5 years old. Examine the fan fail relay bypass jumpers for any signs of overheating. Make sure you have the up-rated cooing fan circuit breaker.

[madstudios]

I noticed lately, that while driving, my DMC-12 has no issues with the cooling system keeping the engine cool. However, when I'm parked or not moving (engine still running), I hear my cooling fans kick on, but my temperature gauge still rises ever so slowly while they're working. Then, when I get to moving again (not very fast, 1st or 2nd gear), the gauge drops back to the preferred temperature (about 180) within seconds. No difference when my A/C is on or off. What's going on?

I had some weird issues with temperature, and I found out the problem was my radiator, really dirty on the inside! I had to replace cause it was leaking too. So far, solved!


Fernando Silotto. Sao Paulo - Brazil
Delorean Vin 3772

[sdg3205]

Can you bring the temperature down by blasting the heat? Do you run an auto bleeder?

[opethmike]

Have you used an infrared thermometer gun to verify the actual coolant temp? It isn't rare for the temp gauge on the dash to show incorrect readings.

[David T]

Have you used an infrared thermometer gun to verify the actual coolant temp? It isn't rare for the temp gauge on the dash to show incorrect readings.

While it is true the temperature gauge can be inaccurate, in this case he said in his first post the temps do go down if he is moving. This would indicate that while the gauge may not read accurately, it at least is responding to hotter and cooler so it does mean things are hotter when he is not moving. Because the fans are so much more important when you are not moving that would lead one to believe that there is some kind of problem with the fans. When the fans come on, the temp should stop rising and begin to drop just as if he started moving. IMHO this is not an instrumentation problem.

[opethmike]

IMHO it very well could be.

[cpistocco]

Can you bring the temperature down by blasting the heat? Do you run an auto bleeder?

I am sure that blasting heat will lower engine temp. (as long as water pump is working and thermostat is open, and there is coolant........ and heater core is not plugged up).

[mluder]

Couple of things.
The car moving could contribute to a quicker cool-down due to more air moving across the radiator... OR... The increased RPMs is sending more power to the fans causing them to turn faster (or more appropriately, the correct speed) and thereby cooling the engine faster. I've noticed my cabin fan speeds up when the engine RPMs increase.

Cheers
Steven

[Bitsyncmaster]

I am sure that blasting heat will lower engine temp. (as long as water pump is working and thermostat is open, and there is coolant........ and heater core is not plugged up).

Actually the heater gets coolant flow even before the thermostat is open.

[cpistocco]

Actually the heater gets coolant flow even before the thermostat is open.

YES- But what good will it do to cool a cold engine? (thermostat is closed)?
Also, the heater by itself would never provide enough engine cooling to keep the engine from overheating if the thermostat is stuck closed.....( That is why I mentioned the thermostat being open) ( although I get your point ).

BTW- You are a Delorean genius bitsyncmaster.... :)

[Nate88]

To resurrect this thread... I had something weird happen yesterday evening along these lines. Dad and I took the car for a ride for around 45-50 minutes most at 50-60mph. The last 10-15 minutes were driving in town with stop lights and stop signs. Temperature level was great all through out the drive rising a bit during the stop lights and signs, but coming down once driving again. Dropped dad off at end of drive and drove only at neighborhood speeds (25mph) to get home. Did have to wait at a stop sign for a min or 2. At that stop sign, temp raised to around 220 mark and fans had kicked on just before. Started driving (again only up to 25mph) and temp dropped a bit. Had a couple more stop signs and turns before reaching my house, but when I reached my street temp was up to 220 again and by the time I pulled it in the garage temp was was at first orange mark. Not wanting to leave it running any more, I shut the car down. I could hear cooling fans running before shutting car off. Did a quick walk around, didn't see any thing amiss. Turned car to RUN position and fans came on again (did not start car). Verified each fan was working by feeling airflow with my hand (they were) and shut it down again. Outside temperature around 80° with low humidity.

This is the first this has happened since replacing parts (listed below). I was in a short 4th of July parade in which outside temps were ~95° and high humidity, car did fine. Just the day before (Saturday) I took it to a big car show in town where there was lines to get in so car was idling and fans kicked on temperature stayed good. I did have my A/C recharged mid June and have used it a bit including on the 4th after the parade and car show.

Water pump and hoses replaced with silicone by PO in 2012. I have replaced the otterstat and thermostat in 2016 (both from Houston). Radiator (2-core from DMC Midwest), DPNW cooling fans, and DMC Midwest stainless coolant bottle was done June 2017. This May I installed the self bleeder kit from DPNW (the kit comes with radiator self bleeder and the thermostat bleeder, I only installed the thermostat bleeder). Their new kit includes a valve which I installed and have kept open.

Things I have done to check include verify both fans working (above), rock screen is clear of any debris, alt/water pump belt intact, and checked coolant level in header bottle (picture attached)57242. Doesn't appear to be any coolant leaks, header bottle level looks good to me. I tried look for the weep hole under water pump with a mirror, but I'm not sure what I'm looking for there.

Tonight I want to check for heat from HVAC to see if heater core could be plugged.

What else should I look for? Why would this have happened or what could have caused this?

[Jonathan]

To resurrect this thread... I had something weird happen yesterday evening along these lines. Dad and I took the car for a ride for around 45-50 minutes most at 50-60mph. The last 10-15 minutes were driving in town with stop lights and stop signs. Temperature level was great all through out the drive rising a bit during the stop lights and signs, but coming down once driving again. Dropped dad off at end of drive and drove only at neighborhood speeds (25mph) to get home. Did have to wait at a stop sign for a min or 2. At that stop sign, temp raised to around 220 mark and fans had kicked on just before. Started driving (again only up to 25mph) and temp dropped a bit. Had a couple more stop signs and turns before reaching my house, but when I reached my street temp was up to 220 again and by the time I pulled it in the garage temp was was at first orange mark. Not wanting to leave it running any more, I shut the car down. I could hear cooling fans running before shutting car off. Did a quick walk around, didn't see any thing amiss. Turned car to RUN position and fans came on again (did not start car). Verified each fan was working by feeling airflow with my hand (they were) and shut it down again. Outside temperature around 80° with low humidity.

This is the first this has happened since replacing parts (listed below). I was in a short 4th of July parade in which outside temps were ~95° and high humidity, car did fine. Just the day before (Saturday) I took it to a big car show in town where there was lines to get in so car was idling and fans kicked on temperature stayed good. I did have my A/C recharged mid June and have used it a bit including on the 4th after the parade and car show.

Water pump and hoses replaced with silicone by PO in 2012. I have replaced the otterstat and thermostat in 2016 (both from Houston). Radiator (2-core from DMC Midwest), DPNW cooling fans, and DMC Midwest stainless coolant bottle was done June 2017. This May I installed the self bleeder kit from DPNW (the kit comes with radiator self bleeder and the thermostat bleeder, I only installed the thermostat bleeder). Their new kit includes a valve which I installed and have kept open.

Things I have done to check include verify both fans working (above), rock screen is clear of any debris, alt/water pump belt intact, and checked coolant level in header bottle (picture attached)57242. Doesn't appear to be any coolant leaks, header bottle level looks good to me. I tried look for the weep hole under water pump with a mirror, but I'm not sure what I'm looking for there.

Tonight I want to check for heat from HVAC to see if heater core could be plugged.

What else should I look for? Why would this have happened or what could have caused this?

Keep the valve closed unless you're actively bleeding air from the system.

[Nate88]

Keep the valve closed unless you're actively bleeding air from the system.

Can I ask why? When I installed the air bleeder I was at a tech day with 4 other cars. All of them, besides mine until I installed it, had the bleeder from the thermostat housing to the coolant bottle. None of them had the valve, so theirs would of been open all the time. Just trying to understand it all. Thanks.

[Jonathan]

Can I ask why? When I installed the air bleeder I was at a tech day with 4 other cars. All of them, besides mine until I installed it, had the bleeder from the thermostat housing to the coolant bottle. None of them had the valve, so theirs would of been open all the time. Just trying to understand it all. Thanks.

So these other cars had just the hose routed straight from that bleeding screw back to the overflow bottle, but nothing to turn the flow on and off? Hmmm, never seen that before. I recall the install of this auto-bleeder on my own car taking that bleeder screw out and attaching the hose with the valve in between back to the overflow tank via a tee that was installed in the existing small hose. That bleeder screw didn't go anywhere before, i.e. if it was opened, it would just dribble/spray out and on the ground. Advice I got was to leave it closed under normal conditions and only open it to expel air trapped in the system. Why? Don't know. And don't think I got an explanation or didn't ask for one. Seemed kosher to me so I went with it. I don't know why your car is getting up to 220 deg F as you're seeing. That open valve was the only thing in your description that jumped out at me.

[Nate88]

So these other cars had just the hose routed straight from that bleeding screw back to the overflow bottle, but nothing to turn the flow on and off? Hmmm, never seen that before. I recall the install of this auto-bleeder on my own car taking that bleeder screw out and attaching the hose with the valve in between back to the overflow tank via a tee that was installed in the existing small hose. That bleeder screw didn't go anywhere before, i.e. if it was opened, it would just dribble/spray out and on the ground. Advice I got was to leave it closed under normal conditions and only open it to expel air trapped in the system. Why? Don't know. And don't think I got an explanation or didn't ask for one. Seemed kosher to me so I went with it. I don't know why your car is getting up to 220 deg F as you're seeing. That open valve was the only thing in your description that jumped out at me.

Correct, from bleeder screw attaching to the existing small hose on the front side of coolant bottle, no valve in between. Mine is exact same way only with valve. Description from DPNW website for the kit is that these auto bleeders work too well and could mask "other issues" which is why they added the valve. I figured I should leave mine open because those cars were open essentially. This is the first time something like this has happened, my otterstat did go bad so the fans didn't come on, but that was 2 years ago and the fans were running this time. Maybe the bleeder is hurting me more.

[Nate88]

So I had the car running for 30-45 min and 2.5 fan cycles. This was all done stationary in the garage.

First I started the car, air bleeder valve open. Once it started warming up a bit turned on the heater. Switching between heater and defrost for 10 or so minutes, the temperature stayed pretty much at first white hash mark. Air got pretty hot. I would think that means the heater core isn’t plugged. After running heat for around 10 minutes, shut off heat continued idling engine. Temperature increased, fans turned on. Fans brought temp down and shut off.

For the second cycle, I shut the auto bleeder valve. Fans turned on temp started coming down but slower. After about 5 minutes or so fans were close to turning off so I revved the engine to around 2000-2500 rpm and temp came down and shut fans off.

Third cycle fans came on again and the temperature pretty much stayed in the middle between the first white hash mark and 220. Didn’t matter if I revved the engine or stayed at idle. Let that go for around 10 minutes or so. I had to stop for a work call which is why I didn’t wait until the fans shut off this time. Auto bleeder valve still closed and still is.

Did this tell me anything? Was what happened yesterday a fluke? Anything else I should try?

[David T]

Do you have the uprated circuit breaker for the cooling fans and the cabin fan? If you don't, the cooling fan breaker can be popping and resetting but in the meantime the cooling fans aren't working and the motor can get too hot. I am not a fan of the auto bleeder. It is a Band-Aid for a leaky cooling system that keeps getting filled with air. If you have a good, tight cooling system with no leaks you do not need an auto-bleeder.

[Nate88]

Do you have the uprated circuit breaker for the cooling fans and the cabin fan? If you don't, the cooling fan breaker can be popping and resetting but in the meantime the cooling fans aren't working and the motor can get too hot. I am not a fan of the auto bleeder. It is a Band-Aid for a leaky cooling system that keeps getting filled with air. If you have a good, tight cooling system with no leaks you do not need an auto-bleeder.

I believe the breaker is original. The updated is 40amps correct?

My cooling system seems tight and like I said had no issues like this before installing the bleeder. My thought was that it’s a “good idea” and it seems many other cars have them so I thought why not. Also I’m trying to get it more ready for DCS which was another reason why I thought the bleeder would be a good idea. I want to upgrade some of the relays and breakers before DCS so maybe I should do this soon.

[David T]

The vendors sell a "kit" with the uprated circuit breakers and some relays. Make sure nothing is melting or heat-damaged, especially circuit #7. While you are at it make sure each and every fuse is the correct size for it's position and leave the cover off but nearby. If you still have the OEM door lock module disconnect the big red wire and stick a 10 AMP in-line fuse on it.

[Jonathan]

I believe the breaker is original. The updated is 40amps correct?

My cooling system seems tight and like I said had no issues like this before installing the bleeder. My thought was that it’s a “good idea” and it seems many other cars have them so I thought why not. Also I’m trying to get it more ready for DCS which was another reason why I thought the bleeder would be a good idea. I want to upgrade some of the relays and breakers before DCS so maybe I should do this soon.

Maybe all you did was introduce some air into the system when you installed the auto-bleeder? It happens. I've done a few "proactive" maintenance jobs on the car and more than a couple of them have caused more problems than they solved. I default to the "if it ain't broke, don't fix it" mindset more often now. And real, actual issues, not just ones I think are happening because I may or may not have heard a noise or noticed something odd. That's my reliability advice for the day for you.

[Nate88]

The vendors sell a "kit" with the uprated circuit breakers and some relays. Make sure nothing is melting or heat-damaged, especially circuit #7. While you are at it make sure each and every fuse is the correct size for it's position and leave the cover off but nearby. If you still have the OEM door lock module disconnect the big red wire and stick a 10 AMP in-line fuse on it.

I'm purchasing a kit and uprating the breakers. I talked to the mechanic that has worked on the car before and he said it sounded like a fan may have cut out. I still need to look for any signs of heat in the relay compartment, but at least I have updated ones coming.


Maybe all you did was introduce some air into the system when you installed the auto-bleeder? It happens. I've done a few "proactive" maintenance jobs on the car and more than a couple of them have caused more problems than they solved. I default to the "if it ain't broke, don't fix it" mindset more often now. And real, actual issues, not just ones I think are happening because I may or may not have heard a noise or noticed something odd. That's my reliability advice for the day for you.

Thanks for the advice! I thought about the introduction of air into the system when I installed the auto bleeder, but that was a month ago with a lot of driving in between. My understanding (and I'm probably wrong) if there is air in the system you'd see it pretty quickly. But like I said above, the mechanic thinks a fan may have cut out so that's my next step to look for. The cooling system is the only thing so far (*knocks on wood*) that has left me stranded, so I'm still nervous when it comes to that.