Intake manifold failure or gasket failure?


My car sprung a leak recently. 1999 BMW 328i. It was not too bad…it would steam inside the hood. I added K-Seal and it worked for a few days but now it came back (though maybe slightly different area).

I was able to spot it coming from the base of the intake manifold…where it joins the engine. My question is, should I be worried that it might be the intake manifold itself that cracked or can I just assume that it is the gasket. By the way, these BMWs use plastic parts, so the intake manifold seems to be made out of plastic. If cracks did develop, would they be visible to the naked eye?

Advice? Replace gasket? Try the bigger bottle of K-Seal? Replace the manifold? Any advice would be appreciated.

Edit: the leak is small, I can drive it around for a while before it starts to leak. By the time I get home from a short trip to the store, it drips in the driveway, just FYI, it seems to be consistent with an intake manifold leak?

How much coolant has it been losing? IM leak seems likely, but there could be more coolant going out the tailpipe than dripping past the IM gasket.

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On my 2005 Corolla,Toyota decided to put a plastic manifold that resulted in a leak down the road.Your bmw probably has the same problem.Look for a tiny crack at the base of the manifold.


little coolant loss. after a 5 mile trip, I add maybe 1 lite coke bottle of water to reservoir…doesn’t overheat -unless I drive it around a lot. No tail pipe drip.

I see no crack unless you mean for me to remove it first and then inspect the IM closely?

Very hard to see cracks in an intake manifold made from black plastic.

Why don’t you rent a coolant pressure tester and test to see if it will hold pressure? You can rent them for free at US auto parts stores. Pressurize a stopped cold engine. Watch the gauge and see if it drops. If it does, it confirms you have a leak. Get out your white paper towels, flashlights and mirror and look for the leak. If the manifold cracked underneath, you should be able to see the leak. Same for a gasket.


Oh cool, I didn’t even know they rented those. I will ask about that, thanks!

Assuming it does leak under pressure, is there a good way to tell if it is the gasket vs. the manifold?

Yes… You can SEE where the leak is coming from.

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You won’t be able to tell if the gasket or intake manifold is leaking until it’s disassembled and inspected.


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Well when it gets under pressure from heat, it leaks right from where the gasket would go, but I was unsure if cracks could form there as well. These things crack far away from the gasket I guess? Egads that would be rough… nah mine looks like it come from the gasket, right between the engine (block?) and the manifold. Ok ty!

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Ah, ok, I guess there are no shortcuts aye? :wink: ty!

The gasket can also leak inside the manifold - so coolant escapes its route and gets sucked into the intake. You have an external leak, at least.

There may some advice about this specific engine at a site for BMW owners. Good luck and please keep us informed.

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Yes it appears so, still, thank you for explaining that. I’ll check the oil for milkyness. Fingers crossed.

Even if it is just the gasket. you have to remove the manifold to get to it so no extra work to check it. With plastic manifolds I am guessing it is seldom the gasket.