MKTurbo Kit - 220 Degree CLT
Senior Member
Joined: Mar 2017
Posts: 675
Total Cats: 192
From: Granbury Texas
I once solved a similar sounding mysterious overheating problem using an unorthodox technique, so just humor me, and give it a shot.
I fully realize providing ideas and diagnostic info for a car without seeing or getting a feeling for it, and by solely generating ideas based on (however detailed they may be) on written forum posts is far from ideal, and I may be inadvertently misled in the process.
With my disclaimer out of the way, let's get to it.
A lot of shops have gas analyzers. I used to have one, and it was an incredibly valuable tool to have.
All you need to do is remove the radiator cap, drain/syphon some of the coolant out (or use a tight fitting funnel on the radiator neck) and get the car good and hot, hold the tip of the gas analyzer probe just inside the rad neck (or the funnel) and brap brap brap the engine as you watch the analyzer screen.
If you have any kind of exhaust gas migration to the coolant, it will definitely be apparent in the form of rising CO and HC values. (Brap braps will force a rich condition, and increase exhaust pressure to exacerbate the problem, if the problem stems form the above mentioned condition)
This test will take however long it takes to get the engine hot. You can also keep checking it as it warms up. Sometimes temperature plays a major role, because certain leaks/cracks/seepages act differently when cold or hot.
Like I said, I used this method as a last resort once, and got results.
You will not lose anything, and even if this test gives you a definite negative result, you will have crossed some of the usual suspects off your list.
(For the record, brap brap means revving and letting go of the throttle repeatedly.)
I fully realize providing ideas and diagnostic info for a car without seeing or getting a feeling for it, and by solely generating ideas based on (however detailed they may be) on written forum posts is far from ideal, and I may be inadvertently misled in the process.
With my disclaimer out of the way, let's get to it.
A lot of shops have gas analyzers. I used to have one, and it was an incredibly valuable tool to have.
All you need to do is remove the radiator cap, drain/syphon some of the coolant out (or use a tight fitting funnel on the radiator neck) and get the car good and hot, hold the tip of the gas analyzer probe just inside the rad neck (or the funnel) and brap brap brap the engine as you watch the analyzer screen.
If you have any kind of exhaust gas migration to the coolant, it will definitely be apparent in the form of rising CO and HC values. (Brap braps will force a rich condition, and increase exhaust pressure to exacerbate the problem, if the problem stems form the above mentioned condition)
This test will take however long it takes to get the engine hot. You can also keep checking it as it warms up. Sometimes temperature plays a major role, because certain leaks/cracks/seepages act differently when cold or hot.
Like I said, I used this method as a last resort once, and got results.
You will not lose anything, and even if this test gives you a definite negative result, you will have crossed some of the usual suspects off your list.
(For the record, brap brap means revving and letting go of the throttle repeatedly.)
This kit will do pretty much the same thing
You can turn the fluid yellow with your breath and then back to blue by pumping air through it.
It can color change multiple times. I test it before I use it.
It's pretty accurate as well. I believe in my tester.
Last edited by technicalninja; Dec 16, 2020 at 11:50 PM. Reason: Only the ninja knows...
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Junior Member
Joined: Jan 2019
Posts: 152
Total Cats: 24
From: NH
Check what things are wired to your Sensor Ground wiring. I have a wideband that has a wire labeled as sensor ground. When I hooked that to the car senor ground when the wideband heater cycled, my fans would kick on. I assume this was because of the ground offset from the high current grounding through sensor ground. The coolant gauge seems particularly sensitive because every time the wideband cycled I could watch temps spike with it. This went away when I got the wideband wiring off of sensor ground entirely.
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Newb
Joined: Nov 2020
Posts: 15
Total Cats: 0
From: N Dallas
Yes, fans kick on at 208 i believe... whatever the default is for MS and it drops temps right back down
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Newb
Joined: Nov 2020
Posts: 15
Total Cats: 0
From: N Dallas
Check what things are wired to your Sensor Ground wiring. I have a wideband that has a wire labeled as sensor ground. When I hooked that to the car senor ground when the wideband heater cycled, my fans would kick on. I assume this was because of the ground offset from the high current grounding through sensor ground. The coolant gauge seems particularly sensitive because every time the wideband cycled I could watch temps spike with it. This went away when I got the wideband wiring off of sensor ground entirely.
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Joined: Sep 2010
Posts: 8,146
Total Cats: 1,087
From: Lake Forest, CA
Perform a block test using the tool Technicalninja posted.
If you don't want to buy the whole tool, Oreilly will loan them, you just have to buy the fluid (less than $10).
Do that, then report back. It's worth a try, easy to perform.
If you don't want to buy the whole tool, Oreilly will loan them, you just have to buy the fluid (less than $10).
Do that, then report back. It's worth a try, easy to perform.
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Junior Member
Joined: Jan 2019
Posts: 152
Total Cats: 24
From: NH
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Newb
Joined: Nov 2020
Posts: 15
Total Cats: 0
From: N Dallas
Sorry for the delay guys, it's been a little hectic with work, family, and Texas freezing over.
I dropped the car off at MER in Cresson because I was sick of diagnostics. The culprit was a bad ground on the intake manifold (not one i touched and didn't know was there) along with some less than stellar wiring on my part. I wanted to follow up since there's so many posts claiming a problem but with no solution.
According to MER, they cleaned up the wiring connections I had made along with checking all grounds. The grounds were all good except for the harness ground that connects on the underside of the intake manifold towards the rear. It was hard for me to see but apparently there's one back there. I'm going to take the car out and check the tune since there's a decent chance it has some bad input data. I would provide pictures but it's incredibly hard to get a phone back there to capture it.
If you're reading this because you have the same problem: read up on the wiring harness in depth and double check ALL grounds, connections, and plugs. Thanks everyone for the suggestions and help
FWIW: I did a leakdown and compression test before I dropped the car off and both had good results so it wasn't a headgasket, cracked block, or anything else.
I dropped the car off at MER in Cresson because I was sick of diagnostics. The culprit was a bad ground on the intake manifold (not one i touched and didn't know was there) along with some less than stellar wiring on my part. I wanted to follow up since there's so many posts claiming a problem but with no solution.
According to MER, they cleaned up the wiring connections I had made along with checking all grounds. The grounds were all good except for the harness ground that connects on the underside of the intake manifold towards the rear. It was hard for me to see but apparently there's one back there. I'm going to take the car out and check the tune since there's a decent chance it has some bad input data. I would provide pictures but it's incredibly hard to get a phone back there to capture it.
If you're reading this because you have the same problem: read up on the wiring harness in depth and double check ALL grounds, connections, and plugs. Thanks everyone for the suggestions and help
FWIW: I did a leakdown and compression test before I dropped the car off and both had good results so it wasn't a headgasket, cracked block, or anything else.
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