After all I've done .... M30 overheating

[FencebusterTDI]

Hey guys- really bounced around the web before posting, but at this point I'm a bit stumped.

Just finished putting together my '85 325e with a slightly modified m30b34. Had the engine out to do clutch work and clean up/respray engine bay.

Put it all back together, bleed coolant using screws on both sides of the thermostat and yippee the beast runs well and stays from the 1/4 mark to 1/2, with the Occasional tickling of 3/4 mark during high speed cruising (it revs pretty high even with the 3.46...)

Couple days later it's prob about 5-10 degrees warmer (85 degrees F) and it hits the 3/4 mark and starts boiling over. Obviously it gets progressively worse until it eventually had to be towed.

The next couple days I worked on it and essentially got the same results. Inconsistent temps with the ultimate result of too-high temps. Thermostat checked, about every bleed procedure known to man, etc

Some info:
-75C thermostat
-head gasket changed A couple months ago to address this problem. Head penetrant/dye tested to look for cracks, about .004 out of true. Once got it bled it ran nice and cool. And CONSISTENT. Actually prob too cool- about one quarter on gauge or even a bit under. Keep in mind temps prob 35-45
degrees F outside at this point.
-engine quite leaky oil-wise, but no coolant leak detectable. Really does hold it.
-no bubbles in rad after HG change.
-derale pusher fan kicks on pretty early (sorry i haven't checked actual temp- just haven't gotten around to it. Have put enough damn time into this thing the last few months)
-car seems to maintain temp better at idle than while cruising. Really starts climbing when consistently driving at 3000rpm plus or when banging through the gears.
-heater is not hooked up.
-if anything, the car is running a bit rich. Plugs, exhaust smell and color, and horrendous fuel mileage seem to indicate that.
-radiator is a custom Al setup at about 1.25" x 17.7" x 26.75." The welding isn't the prettiest I've seen by a long shot, but it doesn't appear to leak at all.
-I've tried a couple different radiator caps. The one it came with is 13psi. The other I've tried is 16psi and it merely takes a little longer to heat up.
-coolant boils out of reservoir whenever it gets that hot. I have a spare cap, but if doesn't seem to want to thread on- perhaps the threads on the tank are a bit chewed.
-builder claims that car ran fine in Dallas area even with regular ac use. I've done a bit to it since then, but all major components are the same. Original build: http://designbolt.com/html/bmwproject11.html


The car is going to a good mechanic next week. We'll see what else is uncovered. Ithe car is in amazing shape and this is pretty much the last obstacle to perfection. I'm willing to make it right ASAP as I'm missing some autocross time, but also getting a bit discouraged:/ save me from buying a miata!

Many thanks


Sent from my iPhone using Tapatalk

[Bearmw]

I would start with a pressure test.

[RagtopE30]

I hate to say this because I am going through similar circumstances but your symptoms strongly indicate head gasket issues. It sounds like the exhaust is getting into the coolant passages at higher rpms. Mine was doing this under moderate boost with my turbo. I would invest in a good quality head gasket and new head bolts (I am assuming you are reusing the old bolts) have the machine shop true up the head and reinstall. Good luck

[CorvallisBMW]

Start with pressure-testing the cooling system. You can also take a sample of your coolant to a shop and have it tested it for hydrocarbons. If you have a leaky HG, they'll be able to tell.

[Wanganstyle]

Your problem is pictured.

The radiator should have no cap on it; bmw radiators never do.

The overflow bottle is responsible for maintaining the pressure and self bleeding air.

Replace radiator with one designed for your e30 by bmw. Run the water lines as intended by bmw design; and yes bmw did sell m30 equipped e30's in south africa.

Problems should go away if head gasket is good.

Sent from my SAMSUNG-SGH-I337 using Tapatalk

[marshallnoise]

How would something like this do for proper bleeding the system?

[CorvallisBMW]

I saw that in their newsletter, it looks overly-complicated for something as easy as bleeding.

[marshallnoise]

I saw that in their newsletter, it looks overly-complicated for something as easy as bleeding.

Seems like a sure fire way of getting all the air out though. I haven't crossed this bridge yet on my m30 swap, so purely speculative speculation.

[FencebusterTDI]

Thanks for the replies everyone. Can't wait to see how it does at a few AutoX events.

I too suspect a minor HG leak... Mechanic ought to be able to find that out pretty quickly. I did indeed buy new head bolts, but who knows- maybe I dicked it up. Pretty simple job though. Agree that going with non-standard radiator and hose setups could introduce unknown variables, but coolant flows fine through this setup and the custom radiator fills all the space up front, thus allowing maximum heat transfer. Also, putting a higher pressure cap on the rad ought to allow the reservoir cap to regulate pressure alone, so not too worried about that. Allows for a little better ac fitment too.

We'll see what the week brings. If it wasn't so much fun to drive I'd just put it in my living room as a conversation piece:D


Sent from my iPhone using Tapatalk

[Red88]

It is extremely important, kind of especially on the m30, to not open the cap on the reservoir or radiator when the temps are hot. It allows the water to expand and boil. There are parts in the head that are 150-160c when you shut the car off and that will instantly boil the coolant (possibly cracking the head) if you open that cap.

[Red88]

It is extremely important, kind of especially on the m30, to not open the cap on the reservoir or radiator when the temps are hot. It allows the water to expand and boil. There are parts in the head that are 150-160c when you shut the car off and that will instantly boil the coolant (possibly cracking the head) if you open that cap.

What kind of head gasket did you get ? A lot of m20 guys complain about the build quality on victor reinz gaskets. It's entirely possible that it was only one batch of m20 gaskets that gave them the bad rap, so yours could be fine if it is VR

[FencebusterTDI]

Gasket was VR. That could be the culprit. Seems to have held for awhile then possibly took a dump and sprung a leak in this hotter summer weather.


Sent from my iPhone using Tapatalk

[Wanganstyle]

IF you suspect head gasket its easy to test; buy/borrow/rent/don't steal - a Leakdown tester / air compressor and leak each cylinder down. It pressurizes each cylinder and you will be able to see leaking into oil or water from it.

any decent shop will also have one.

[FencebusterTDI]

Update

Haven't had too much time lately, but finally tried a few different things.

I do believe the coolant reservoir cap was leaking more than it should have been. I bought a new reservoir and the cap threads on straighter and seals tighter----(anyone notice their caps threading on inconsistently? Even my new one with a new cap doesn't like to go on straight...

Anyway, I didn't have any head gasket leak as indicated by coolant testing and exhaust testing by a mechanic. Hallelujah.

The car would occasionally work well and maintain temperature, but it was highly dependent on perfect bleeding and outside temp.

So... after all this, I finally looked at some engine bay pictures and think I may have found a solution. Some asshat between me and the original owner may have routed coolant hoses wrong. I notice in both the original build pictures and other M30 swaps that two hoses typically run along the left side of E30 M30 swaps. Mine doesn't have that (as in the original build pics at designbolt.com)

My heater core isn't hooked up (since the build), but I think that there may be two hoses mounted opposite of one another coming from the pump, heavily impeding flow (the pump does move water well).

I've searched around on the forum and tried to get a good grasp on hose routing for an E30/M30 swap. Is there any specific thread or site that comes to mind when it comes to this? Is it standard to have a coolant fitting coming off the back of the head (mine seems to have been blocked off if that's the case)?

This would not be a problem if I had a well-assembled setup between the original owner and I. This thing is a well-preserved jewel, but someone messed with it a bit at some point... Any help appreciated. I'm a pretty experienced mechanic, but it would help to see some detailed photos of coolant hose routing and where the "T's" and elbows go in. Thanks

[marshallnoise]

Haven't had too much time lately, but finally tried a few different things.

I do believe the coolant reservoir cap was leaking more than it should have been. I bought a new reservoir and the cap threads on straighter and seals tighter----(anyone notice their caps threading on inconsistently? Even my new one with a new cap doesn't like to go on straight...

Anyway, I didn't have any head gasket leak as indicated by coolant testing and exhaust testing by a mechanic. Hallelujah.

The car would occasionally work well and maintain temperature, but it was highly dependent on perfect bleeding and outside temp.

So... after all this, I finally looked at some engine bay pictures and think I may have found a solution. Some asshat between me and the original owner may have routed coolant hoses wrong. I notice in both the original build pictures and other M30 swaps that two hoses typically run along the left side of E30 M30 swaps. Mine doesn't have that (as in the original build pics at designbolt.com)

My heater core isn't hooked up (since the build), but I think that there may be two hoses mounted opposite of one another coming from the pump, heavily impeding flow (the pump does move water well).

I've searched around on the forum and tried to get a good grasp on hose routing for an E30/M30 swap. Is there any specific thread or site that comes to mind when it comes to this? Is it standard to have a coolant fitting coming off the back of the head (mine seems to have been blocked off if that's the case)?

This would not be a problem if I had a well-assembled setup between the original owner and I. This thing is a well-preserved jewel, but someone messed with it a bit at some point... Any help appreciated. I'm a pretty experienced mechanic, but it would help to see some detailed photos of coolant hose routing and where the "T's" and elbows go in. Thanks

The two engines most commonly used in m30 swaps is the b34 and the b35. The b35 does not have the coolant pipe on the back of the head and the b34 does. However, people do block it off when attempting to move the engine farther back.

Having not completed my swap yet, I can't comment. But I would tell you what I would do: Look at the Bentley manual or the shop manual for an m30 equipped car side by side with an e30.