[ro881e]

I spent ages trying to find a guide for the OFHG plus cooler, this YouTube video was by far the best.

I did it without draining the coolant and I regretted it. Draining coolant is super easy and saves you making a massive mess! Also, get a massive syringe to extract oil from under the oil filter before removing, saves a worse mess

[fgpalmer71]

Originally Posted by ro881e

I spent ages trying to find a guide for the OFHG plus cooler, this YouTube video was by far the best.

I did it without draining the coolant and I regretted it. Draining coolant is super easy and saves you making a massive mess! Also, get a massive syringe to extract oil from under the oil filter before removing, saves a worse mess

Thanks +100000! I've been trying to find that!

I'm replacing the coolant reservoir and flushing the coolant anyway. I broke the float in the reservoir and found what seems to be old oil stuck to the bottom of it. So the safest bet I think is to completely flush the system. I've got new vaccum lines from FCPeuro and I've been reading about the fragility of all of these coolant lines, thinking of attempting to knock those out as well...same time. I've got a battery issue to deal with now too.

Is there anything else that I might as well take care of at the same time as this OFHG and coolant tank reservoir replacement? If something is easier to deal with now, when I have those things apart, I'd rather do it and be done for now.

[ro881e]

No worries! Only other items are water pump and thermostat but you mention These were done recently so I think you are set. Maybe change the oil out incase you have coolant in it, and you have the oil filter out anyway?

[fgpalmer71]

Originally Posted by ro881e

No worries! Only other items are water pump and thermostat but you mention These were done recently so I think you are set. Maybe change the oil out incase you have coolant in it, and you have the oil filter out anyway?

Yep, water pump and thermostat were changed a few months ago. I'll definitely do an oil change. I'm pretty sure the oil is good. But I'm basing that solely off of the visual inspection of whats under the oil cap

[GSB]

Here's my terrible experience with that pathetic rubber gasket on the oil filter housing...

At about 87k miles, my 08 335i blew the plastic pipe above the radiator (coolant return to reservoir). I repaired the pipe, plus $30 of new coolant. A month later, it blew again. So I replaced the pipe with a custom stainless pipe, plus $30 of new coolant. Because I'd lost the coolant each time, I had not noticed that a gray sludge was developing in the coolant reservoir. There was no sign of it when I refilled the new coolant. Then the coolant level indicator fell off the float and disappeared into the reservoir. After a difficult retrieval, I found that it was all soft and crumbly. What the ?!? And that's when I noticed the sludge - not floating in the coolant but hiding in gobs under the top of the reservoir. I had no idea where it was coming from, and I didn't have the time or the funds to deal with it right away. Later, I discovered external oil leakage below the oil filter housing and pure black oil now in the cooling system. That's when I found this forum and others who were experiencing this OFHG failure. I ordered the new gasket, but before it arrived, the serpentine belt suddenly shredded and wadded up in a rubbery bird's nest of threads under every one of the pulleys and the tensioner. EMERGENCY failure on the freeway, with no power steering or alternator. I was extremely fortunate that the shredded belt wasn't forced through the front crank seal and into the timing chain as has happened to many others!

I had to remove the radiator to replace the belt and that accursed oil filter housing gasket. I cleaned the engine and the mating surfaces meticulously and used Permatex Optimum Grey Gasket Maker as a dressing (Permatex claims "Maximum vibration resistance, with outstanding resistance to oils, cooling fluids, and shop fluids. 15% more flexible than Ultra Grey. Maximum temperature resistance: -65F to 700F intermittent"). There was no way in heck that I was going to do all of that work to replace the gasket without improving that seal. Just because some twit at BMW chose to use a skinny rubber gasket in that critical location, does NOT mean it was a good idea. My Hondas have NEVER had issues like this!

After that repair, I flushed the cooling system over and over again with plain distilled water, running it through the engine to full operating temp, but it hardly touched the oil sludge inside. I looked into radiator flush products and chose one carefully to be compatible with the BMW cooling system. It did nothing. So, I tried flushing with "Super Clean" (Full Concentrate All Purpose Cleaner/Degreaser Biodegradable & Phosphate Free) mixed 50/50 with distilled water. The sludge started coming out in gobs with each flush and drain. It was packed in large gelatinous blobs throughout the engine, radiator, water pump, thermostat and fittings everywhere. I flushed again and again, with longer and longer run times (up to a week) until the system came clean. Finally, I flushed and drained one more time with pure distilled water, then added the $30 of new coolant.

Then the crappy new "Gates" serpentine belt started squealing. Then the pulleys and tensioner started whirring and grinding. So I replaced the belt (again) with a "Continental" belt, plus new pulleys and tensioner... which require removal of the radiator, plus $30 of new coolant.

Then the plastic quick-fit hose coupling to the top of the radiator cracked and leaked all of the coolant. I contemplated a JB-Weld repair, but as I removed the plastic fitting, it broke clean off and literally crumbled and turned into a brown putty as I rubbed it between my fingers. It became clear that a serious chemical reaction had taken place. The plastic coolant fittings are impervious to oil or to coolant on their own, but when combined, the plastic simply dissolves. Not only that, but all of the rubber hoses and gaskets throughout the cooling system had softened and swelled really badly. So I replaced that plastic fitting and its hose, along with several other hoses and seals, plus $30 of new coolant.

Then the plastic water pump cracked. $400 for a new pump and thermostat, plus $30 of new coolant.

Then the radiator cracked. So I replaced the radiator, plus $30 of new coolant.

Then the plastic flange on the front of the cylinder-head, bringing coolant from the thermostat, crumbled and fell off, spewing all of the coolant. So I replaced that hose and upgraded the flange with an aluminum one, plus $30 of new coolant.

Then the brand-new water pump cracked again - after 2 months. I replaced that under warranty, plus $30 of new coolant.

In the meantime, all 6 injectors had begun to fail, sticking wide open, pumping raw gas through the exhaust system, smoking prolifically until a creamy sludge began dripping out of the tail pipes, and misfiring so badly that the car became undriveable, throwing hundreds of error codes. So I replaced the injectors, plugs and coils. The engine ran well again, and the exhaust system slowly burned off the sludge, but the oxygen sensors couldn't take it, and failed. So I replaced the O2 sensors.

By then, the valve cover gasket had begun leaking oil all over the exhaust manifold and turbos, causing choking white smoke to pour out of the fenders and through the ventilation system into the cabin. When pulling up at a traffic light, people would roll down their windows to yell, "Your car's on fire!!" My windows were already open as I gasped for fresh air, so I replied, "Yeah, thanks, it's been burning for several months... precision German engineering." The worst part of THAT problem is that oil from the valve cover leaks down the back of the engine, where it gets into the rear turbo coolant line, destroying the rubber hose, and BAM, there went another $30 of coolant and one of the most difficult repair jobs I've ever attempted without removing the engine!

Then the water pump cracked again (out of warranty this time). I'll be installing the 4th water pump this week, plus $30 of new coolant.

Never in my LIFE have I experienced so many catastrophic failures that have left me stranded on the side of the road. MAN, how I hate my BMW... and the twit who designs those plastic parts and plastic water pumps and flimsy rubber gaskets that cause thousands of dollars of collateral damage... plus the monthly $30 of new coolant!

[fgpalmer71]

Thanks for sharing that. I've been putting this off for sure. Your story sounds as if it started pretty much just like mine!! I'm now going to assume that the sludge found on the snapped off coolant reservoir float has made its way throughout my cars cooling system. I'll plan to go ahead and replace all of the coolant lines and hoses now, in addition to the reservoir. I'll take your flush method too and see what comes out of my car! I hope I can head this off before the cascade effect takes place.

[GSB]

You're welcome. And yes, the point of my post is to help other owners to see the necessity of repair at the very FIRST sign of oil in the coolant, or oil weeping down the front of the engine underneath that stupid oil filter housing. Because waiting is fatal to the entire cooling system, serpentine belt and pulleys. One owner's belt even wadded up around the crankshaft and went clean through the crankshaft seal, ruining the seal. Another horror story that cost him a fortune!

Note that I did not replace my reservoir, and it appears to be just fine, after another year of use. The level indicator is history, but I can still see the coolant level without it.

[fgpalmer71]

I did notice that fact. I already have the new reservoir and cap in the garage, along with the full OFHG kit from FCP. I'm going to go ahead and order the upper and lower radiator hoses and the coolant line that runs from the reservoir to the radiator. Which other lines would you recommend that I replace? I would like to do this all at once ......reservoir, OFHG's, lines and flush....and be done with it.

The water pump and thermostat were changed in June 2020, a few weeks before I bought the car, @78k. I'm hoping any sludge that may have made it into the new pump can be cleansed without ruining it. I've been thinking the sludge found on the snapped off reservoir float may have been from a previous OFHG leak. I deduced this purely from the visual state of the OFH and the fact that there was nothing milky underneath the oil cap and no signs of oil in the coolant visually.....apart from the sludge found on the bottom of the float stick. I can't get a response from the previous owners mechanic so I'm now assuming it's actively leaking internally.

[GSB]

I would DEFINITELY suspect that oil is currently leaking into your coolant. A skinny rubber gasket separates the oil and coolant in the Oil Filter Housing. When it blows, the oil pressure appears to exceed the coolant pressure, thus I found NO coolant in my oil, only oil in my cooling system. The oil and coolant do not immediately mix, so the coolant may seem to look normal (especially if someone replaced the coolant right before you bought the car). I would not assume a previous OFHG repair. I'd suspect a cover-up (new coolant). A gelatinous sludge builds up in invisible locations all around the cooling system, blocking smaller channels like the radiator, and it eats away the plastic fittings, rubber hoses and o-rings everywhere.

The water pump seemed to take the "Super Clean" degreaser without any ill effects. I ran that stuff through the system until hot, then drained it out and repeated several times until the sludge was pretty much gone. Each time, I left it a little longer, until the last cycle, which I drove for a week or two. Then I rinsed and flushed a few times with distilled water before replacing the BMW coolant. Be sure to replace the critical rubber and plastic parts before you throw in the BMW coolant.

Possibly the most important fitting to replace, aside from those you've mentioned, is the plastic flange on the front of the cylinder-head (close to the OFH), bringing coolant from the thermostat. I've read that other people broke that flange while doing the OFHG job. I was very careful with mine and didn't remove it during the job, but later, it just crumbled and fell off while driving. The hose was in bad shape too. The new hose and plastic flange come as a single assembly. You can find upgraded aftermarket hose assemblies with an aluminum flange.

One rubber hose that softened up really badly and ballooned, was the short U-bend between the thermostat and water pump. Another short hose connects the pump output to a metal pipe that feeds the block, right between and below the exhaust manifolds. I did not replace that hose, because it has a metal clip that's impossible to access. But that hose is bad, and I'm about to replace it soon... with a Dremel tool to cut the clip off.

The coolant return line to the reservoir has a plastic tube that crosses the top of the radiator. That one is a ticking time-bomb, and mine burst in two different locations. I replaced that tube with a stainless tube.

Shortly after that, the plastic radiator cracked. While you have the radiator out to do the OFHG job, I suggest you replace it. They typically fail at around 120k anyway. I bought a "Pacific Best" Radiator from Cooling Direct at Amazon. It's identical to OEM and has lasted just fine. I did not buy any of my parts from BMW. I found identical OEM parts for less than half the price. Note that the radiator differs in the manual and automatic cars.

[jmiske4]

i may have a relevant or similar issue my 08 335i gets really hot and im not sure what it might be and i have a cold air intake on my n54 if that makes any difference. the dealer told me my car should sit between 180-200F but my car will get as hot as 250 all the time i cant really drive the car without it throwing a code everytime i do so i dont drive it very far so i keep it from getting too hot.

im also new to the e90 post as well so im sorry if my post isnt the best


2008 335i
109XXX miles

[fgpalmer71]

Originally Posted by jmiske4

i may have a relevant or similar issue my 08 335i gets really hot and im not sure what it might be and i have a cold air intake on my n54 if that makes any difference. the dealer told me my car should sit between 180-200F but my car will get as hot as 250 all the time i cant really drive the car without it throwing a code everytime i do so i dont drive it very far so i keep it from getting too hot.

im also new to the e90 post as well so im sorry if my post isnt the best


2008 335i
109XXX miles

Welcome.

For reference, my 335i is always above 200F when its warmed up. It lives 2 notches below the 250 degree mark. It's never seen 250F and never thrown a code related to overheating. Do you have a scanner to pull the codes It's throwing? If so, and you have done so already, what codes are popping up?