Overheating

[jwrayth]

About a year ago to the day my water pump started to fail. Over winter I went into the VoD and replaced it along with some smaller jobs. Since March I've been struggling to get the cooling system to operate correctly when previously it was solid other than a slight leak at the radiator. I'm just about at the end of my tether with it, so thought I'd check in for some collective wisdom on what to do next.

Things changed;

New Water Pump
New Thermostat (tested before fitting)
New Otterstat (tested before fitting)
New Temperature Gauge sender
New Radiator
New Fans
New coolant tank pressure cap
New silicone hoses for VoD and Waterpump
New heater valve and silicone hoses
New belts for A/C, and Alternator
Bled at radiator until no air seen
Bled at thermostat with rear end raised until no air seen
System holds 15 psi for 30 minutes using a coolant pressure tester
No leaks observed from the system, including using an inspection camera into the VoD


When testing the vehicle;

Start engine with heater on and cabin fans running
Remove coolant cap to observe good coolant flow that varies appropriately with revving the engine
As engine warms up, tested vents in cabin to confirm good heat coming from heater core
As engine warms up, observe drivers side of radiator warms up, with passenger side following over time
As temperature gauge creeps upwards, fans to not engage at any point
Jumping the fans at the otterstat engages the fans as expected
Gauge reaches just below 220 mark. Stop engine and leave to cool completely
Laser thermometer reading shows 118f temperature at thermostat housing exterior
No evidence of head gasket issues present (oil looks good, coolant looks good. No signs of exhaust fumes in coolant during testing)


So with all that in mind, I'm stuck with where to go next. I've bled the system 3 times, and on the third attempt saw no air bubbles during the bleeding process. New gauge sender could be bad, but that seems very unlikely.

== EDIT ==
Sorry for generic topic title. Clicked submit too early and can't change it...

[DeLoreanGo Arran]

What is the actual problem though? Are you saying the only issue is that the engine is "probably hot" but that the only data that indicates this is the gauge? Was the old temp sender definitely bad? Your laser thermometer isn't reading a particularly hot value I'd say.
Also how is the otterstat attached? Cable ties or a single clip?

[eseethal]

I have a similar story, I am pretty sure it is the new temperature sender. If you still got your old one you could try it again. Unfortunately I threw mine away after replacing it. The symptoms on my DeLorean are the same as with yours. 220 mark and even above, but the cooling systems temperature is in it's normal range. I've been driving around like this for a couple of months now and got used to ignoring the temperature gauge. I am not sure if putting a new sender in will change this symptoms (except maybe from a different vendor, I bought mine through Delorean.eu.).

good luck............Eugen

[jwrayth]

What is the actual problem though? Are you saying the only issue is that the engine is "probably hot" but that the only data that indicates this is the gauge? Was the old temp sender definitely bad? Your laser thermometer isn't reading a particularly hot value I'd say.
Also how is the otterstat attached? Cable ties or a single clip?

Otterstat is currently the new UK screw-in (https://www.deloreango.com/uk/screw-in-otterstat.html) type and new coolant pipe, but same results with my OEM version that was working before (and was attached with a clip and cable-tie). But since you sell the UK ones you know they are good :)

Old sender seemed to work fine. When I was in the VOD I had to replace it as the old ring terminal was corroded and separating from the wiring, and when I tried to back-off the nut on the sender the entire threaded portion from the sender started to spin and come apart. So I had to replace my old sender since it was now no longer usable.

So the engine seems "probably hot" as you say but I've not run past the 220 mark for fear of causing undue damage/stress to the engine. I do have a replacement sender with the spade fitting (yet again from yourself, so thanks!), but was hoping for some wisdom on diagnosing a bad sender so I can test the newer one before going to the effort of draining and replacing.


I have a similar story, I am pretty sure it is the new temperature sender. If you still got your old one you could try it again. Unfortunately I threw mine away after replacing it. The symptoms on my DeLorean are the same as with yours. 220 mark and even above, but the cooling systems temperature is in it's normal range. I've been driving around like this for a couple of months now and got used to ignoring the temperature gauge. I am not sure if putting a new sender in will change this symptoms (except maybe from a different vendor, I bought mine through Delorean.eu.).

good luck............Eugen

That's curious as my sender is from delorean.eu as well. Maybe coincidence, maybe not. Anyone have multi-meter readings for what the sensor should be putting out at the 220 mark?

[eseethal]

Wow, that definitely is no coincidence! Could you try your replacement sender?

Eugen


That's curious as my sender is from delorean.eu as well. Maybe coincidence, maybe not. Anyone have multi-meter readings for what the sensor should be putting out at the 220 mark?

[DMC-Ron]

One thought might be to electrically connect up your spare new sensor and place it in a thermos of nearly boiling water, turn on the key, and see what reading you get. Or, if you have a portable hot plate, bring it to a boil and verify the 212 degree reading.

Ron

[dmc4087]

What orientation do you have the new otterstat/pipe fitted? I had cooling issues a few years ago because I fitted the pipe with the otterstat to the top - air bubbles were then being trapped (I presume) and it wasn't activating the fans.

[David T]

I would suspect the temperature gauge is not accurate. After about 20 minutes of idling the fans should start up at about 200 degrees.

[jwrayth]

What orientation do you have the new otterstat/pipe fitted? I had cooling issues a few years ago because I fitted the pipe with the otterstat to the top - air bubbles were then being trapped (I presume) and it wasn't activating the fans.

Facing upwards, as the OEM one was also. Though as I say, even if I manually jump the fans the temperature continues to rise.


What orientation do you have the new otterstat/pipe fitted? I had cooling issues a few years ago because I fitted the pipe with the otterstat to the top - air bubbles were then being trapped (I presume) and it wasn't activating the fans.

I'm going to spend some time Saturday doing a very similar test! Drain the block, pull the old sender and test side-by-side.

Consensus being the sender/gauge is reporting incorrectly is reassuring to hear though, as I've had nothing but trouble in my cooling system as part of my VoD journey so it'd be nice if this last problem is an "easy" fix!

[jwrayth]

Did some searching over my lunch break and found a site with some useful details (http://www.nrdvana.net/project-electrical.html).


The stock temperature sensor is a resistor that starts at several thousand Ohms and drops logatirhmicly as it heats up. Using the stock gauge as a reference, 100 °F is 1000Ω, 220 °F is 100Ω, and 260 °F is 50Ω.

Going to try and make some readings using that as a starting point tonight :)

[eseethal]

I am very interested in your tests! Fingers crossed that it's the new sensor!

Eugen

[eseethal]

Going to try and make some readings using that as a starting point tonight :)
Were you able to make some readings in the meantime? I "fixed" my problem with the obviously wrong sender already, I just put a varable resistor (0-100 Ohms) inline, so I could adjust the correct reading when the engine is warm (I added probably 25 Ohms). This seems to work fine, although I know it's not the right way to fix this as the resitance of the sensor is not linear. But this was much easier than changing the temperatur sender :-)

Eugen

[Bitsyncmaster]

Were you able to make some readings in the meantime? I "fixed" my problem with the obviously wrong sender already, I just put a varable resistor (0-100 Ohms) inline, so I could adjust the correct reading when the engine is warm (I added probably 25 Ohms). This seems to work fine, although I know it's not the right way to fix this as the resitance of the sensor is not linear. But this was much easier than changing the temperatur sender :-)

Eugen

This thread has data of testing the gauge sender.

http://dmctalk.org/showthread.php?15056-Electronic-Otterstat

[Morpheus]

As engine warms up, observe drivers side of radiator warms up, with passenger side following over time.


This stood out to me. When one side of the radiator is cooler than the other, then it typically means you still have trapped air in it. Try bleeding the radiator again, but do it cold with a pressure tester.

[David T]

[/LIST]

This stood out to me. When one side of the radiator is cooler than the other, then it typically means you still have trapped air in it. Try bleeding the radiator again, but do it cold with a pressure tester.

Trapped air would cause the top to be colder than the bottom, where the air is (on the top) the hot coolant can't reach and warm up.

[Morpheus]

Trapped air would cause the top to be colder than the bottom, where the air is (on the top) the hot coolant can't reach and warm up.

I agree, you would think that physics would defy what I wrote. If I hadn't been shown this phenomenon by Dave Swingle in person on a car that was having a strange overheating problem, I wouldn't have believed it either. However, I have... and he was right. I bled the radiator again, and a bunch more air came out. Afterward, the temp didn't get much higher than the first mark on the gauge. I merely suggested that the OP try, it certainly can't hurt.


Sent from my iPhone using Tapatalk

[dn010]

I can attest to one side being colder than the other, this happened to me after I installed my new aluminum radiator. I didn't overheat but I always feel around to make sure things are circulating. However, I parked on an incline and left the bleed screw open on the pump for a while until I got the air out, then instantly the radiator was the same temp throughout.

[dn010]

Facing upwards, as the OEM one was also. Though as I say, even if I manually jump the fans the temperature continues to rise.

You should also change this so that the otterstat is facing downwards.

[ritztoys]

I parked on an incline and left the bleed screw open on the pump for a while until I got the air out, then instantly the radiator was the same temp throughout.

I take it you parked your car with the radiator "down", and allowed the 'air' @ the water pump/thermostat housing to bleed out slowly.

The reason I ask is I need to replace my coolant as when it gets old it can corrode the aluminum pipes in the cooling system, ask me how I know!

[dn010]

Yes, radiator was lower than the engine, there were times I've even had to raise the back of the car up with a jack a few times depending on the situation. I've too have had to replace rotten aluminum pipes, especially the passenger side rear pipe that has a clamp around it securing it to the frame - it was corroded enough a hole appeared.

I've drained and refilled the DeLorean cooling system dozens of times over the past 15 years. It isn't fun compared to a 'typical' vehicle but as long as you're thorough you'll be fine, especially if you have an auto bleeder installed [I do not].



I take it you parked your car with the radiator "down", and allowed the 'air' @ the water pump/thermostat housing to bleed out slowly.

The reason I ask is I need to replace my coolant as when it gets old it can corrode the aluminum pipes in the cooling system, ask me how I know!

[ritztoys]

Thanks dn010,

That's what I have done in the past, sloping grade away from the garage. No auto bleeder, just 'bleeding air' out of the system while not getting engine too hot in the process.
My pipe corrosion was under, where the old 'original rubber hoses' were attached to the pipes(26 yrs ago), everything is good now new rubber though out whole cooling system.