Overheating issues/ causes

#1

Hello all,

This weekend I developed a slow leak in a radiator hose and Ran about 2 laps(NHMS) with the factory temp gauge in the RED zone.

I replaced the hose and everything was fine for the rest of the day. it was a cool day.

The next day was a little warmer (85~90 degrees) and toward the end of the day the Temp gauge was over the half way mark and in to the 3/4 mark by the end of the last session. When I pulled in to impound the overflow tank was full and steam was coming out overflow hose.

All I have is the factory engine mounted fan.

I have never had overheating issues with this car before running the same setup.

Did cooking the engine the day before cause this? Any suggestions? Bad head gasket? still have air in the system after the hose change?

#2

I would say air in the system might have done it. I just replaced all my radiator hoses this weekend. I then filled it with coolant and left the cap off the overflow tank and started the car. It took awhile, but once the thermostat opened and the car was nice and hot some bubbles started appearing in the overflow tank. Once they stopped appearing the system was bled, and I topped off the overflow tank and put the cap on to take it for a drive. Then once cool again I topped off the overflow tank one more time.

#3

Been there, done that.
Cooked.
As it heats up the already warped cylinder head and/or about to give way head gasket let out the pressure and the temp rises/overflow develops.

Sorry to hear of your misfortune.

R Patton

#4

King Tut wrote:

It’s been my experience that the M20 is a little harder to bleed than that. Now I use the idle-until-warm, heat-on-high, crack-the-bleeder-screw method while the front of the car is elevated on ramps, a jack, a hill, whatever to make sure that screw is the high point in the system. That seems to get most of the air out, then a couple drives around the block jostle free any remaining air pockets in the system and it’s good to go.

#5

Patton wrote:

[quote]Been there, done that.Cooked. As it heats up the already warped cylinder head and/or about to give way head gasket let out the pressure and the temp rises/overflow develops.Sorry to hear of your misfortune.
R Patton[/quote]

So what I think I am seeing. Combustion gases from the Cylinder are getting past the Head Gasket (HG) and are heating the water super hot. This would also explain why my normally clear water has turned a murky gray. There are no signs of of water in the oil or Oil in the water. there is no smoke or steam out the back.

Andrew suggested I do a cooling system pressure test. I am guessing a compression test should also help to confirm it.?

What is the best next step? I dont have the $$$ for a complete rebuild. Should I just change the HG? what about machining to the head? Or should I just go with a Junkyard motor?

What HG and from What Vendor?

BTW I am also replacing the trans :slight_smile: Fun weekend!

#6

Steve D wrote:

[quote]King Tut wrote:

It’s been my experience that the M20 is a little harder to bleed than that. Now I use the idle-until-warm, heat-on-high, crack-the-bleeder-screw method while the front of the car is elevated on ramps, a jack, a hill, whatever to make sure that screw is the high point in the system. That seems to get most of the air out, then a couple drives around the block jostle free any remaining air pockets in the system and it’s good to go.[/quote]

Yeah I thought about the bleeder screw but it appears that the overflow bottle is actually a higher point in the cooling system. I will try jacking and cracking the bleeder screw, but it always seems hard to see if bubbles or just coolant comes out of it.

#7

I’ve not done a pressure test, so this shadetree can’t help on the proceedure.

Head comes off and gets sent to the shop for evaluation/flatness/cracks.Contemplate a head rebuild job… Purchase new headgasket and reassemble. Easy, if you’ve done it several times.From your post, this is the first in a long stream of learning events that you’ll have to live through…unless you have a big wallet. But then, you wouldn’t be racing here.

Good luck, RP

#8

Learning to fix things is part of the sport. No i dont have a big wallet.

I have never seen plus like these, sorry for the blurryness. These have a total of 4 track days on them.

they have white and red deposits on them.

Compression ( HF compression tester so exact PSI is questionable)

1: 135
2: 130
3: 130
4: 100
5: 130
6: 130



#9

That definitely does not look good.

http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp

[quote]Deposits
The accumulation of deposits on the firing end is influenced by oil leakage, fuel quality and the engine’s operating duration.[/quote]

#10

There is a test any mechanic shop should have. It uses a special fluid that changes color when it comes in contact with exhaust gases. The can test for exhaust gas in your coolant reservoir.

The exhaust doesn’t have to heat up your coolant it just pressurizes it and blows it all out into your catch can. My turbo motor is currently having the same issue for the 6th time. I am now upgrading from mls to copper with stainless o-rings. My block and head were milled straight although they were within factory specs. I suggest you do the same. There are 2 styles of head bolts. You should have the newer ones with regular hex heads on them. VAC sell an ARP stud kit that will clamp better and make it easier to line everything up. A new stock gasket should work fine for a spec e30 motor. Do not buy an mls gasket!

#11

I’ve not heard the “combustion gases made my water grey” theory before. I don’t think that the primary symptom of combustion gases in the water is going to be a water temp increase. Water is already in contact with the very hot cylinder walls, yet it’s under relatively low pressure. High pressure combustion pulses are going to blow water out all over.

As the guys said, a problem bleeding the system does fit your symptoms.

Pulling the head is kinda a last resort move and you might not be there yet. Drain your water and oil and take a hard look at it. Go get a coolant pressure tester from Harbor Freight, one of the adapters in their kit fits. Bleed it like a mofo. Spend a couple nights doing everything you can short of pulling the head and if nothing fixes it, the head will have to come off.

Aluminum expands more then iron. The head gasket has a limited ability to support dissimilar movement (expansion) on it’s two surfaces. Eventually it fails. If the aluminum gets hot as heck, it fails earlier.

#12

When replacing or removing the thermostat, drill a 3/16" hole where the arrow is (up) and reinstall. This allows water to reach your stock temp gauge regardless, and also allows air to escape when filling the system. I haven’t used my bleed screw in 10 years. CB

#13

You guys are gonna hate me for this, but I have to say thank you to Scott (Ranger). He pleaded with me to do every test there is before removing the head. I gave in and found another leak in the cooling system. It didn’t leak water when running, but once under the pressure test water was everywhere. fixed the leak and bled the system, the engine ran for 30 mins with out over heating.

I bought a new Compression tester and the Compression is all cylinders is 145~148 dry, 150~153 wet.

I bought a leak down tester as well, but one of the gauges is broken so it is going back and I will have finish testing that tomorrow.

It is looking like I Dont have to replace the HG.

I do now have an oil leak coming from the Oil Valve area where the oil filter screws in. i will have to work on that one.