Typically, you should not apply sealant to water pump gaskets. Most gaskets are designed to seal on their own; only use sealant if the vehicle’s service manual or gasket kit explicitly instructs it, and then only as a thin bead along the mating surfaces.
Water pumps and their gaskets seal the cooling system between the pump housing and the engine block. Getting this seal right is crucial to prevent coolant leaks and overheating. This article explains when sealant is appropriate, what kind to use, and best practices for installation.
When to use sealant with water pump gaskets
Guidance varies by gasket type and manufacturer; the following scenarios cover the common cases where sealant is recommended or allowed.
- The service manual or gasket kit instructs you to apply sealant to the water pump gasket or the mounting surfaces.
- The gasket is a flat paper/composite type that lacks a built-in sealing bead, and the manufacturer specifies adding a thin bead of sealant to improve the seal.
- The mounting surfaces are slightly imperfect or damaged, and the instructions allow a small amount of coolant-safe sealant to compensate (replacing the gasket is preferred if possible).
- The pump uses a sealant on legacy engines where the original design relied on gasket sealant; follow OEM guidance in these cases.
In all cases, avoid applying sealant to bolt holes, threads, or inside passages, and avoid excessive amounts that can shed into the cooling system.
Best practices and sealant options
When sealant is permitted, choose a coolant-compatible, non-hardening sealant and apply it sparingly according to the manual. Here are guidelines to help you pick and apply sealant correctly.
- Use a non-acid, automotive-grade RTV silicone sealant that is compatible with the coolant and gasket materials (for example, grey or black RTV). Do not use epoxy-based or petroleum-based sealants in contact with coolant systems.
- Apply a thin bead along the gasket's perimeter on the side specified by the manual; do not apply sealant to bolt holes or the interior passages.
- Coat both sides of a paper/composite gasket lightly if the manual calls for it, and ensure surfaces are clean and dry before installation.
- Torque the pump bolts to the manufacturer's specification in a crisscross pattern to ensure an even seal and avoid gaps.
Note that many modern water pump gaskets are designed to seal without any sealant calls; if you skip sealant when it is recommended, you may risk leaks. If you are unsure, consult your vehicle's service manual or a qualified technician.
Summary
Bottom line: Do not automatically seal water pump gaskets with sealant. Follow the vehicle’s service manual. If sealant is specified, use a thin bead of a coolant-safe, non-hardening RTV sealant around the gasket edges as directed, and avoid sealant in bolt holes or coolant passages. Use the correct gasket type and ensure all surfaces are clean before installation to prevent leaks and coolant contamination.
How long to let a water pump gasket dry?
The product dries tack free in one hour and fully cures in 24 hours. Cure times will vary with temperature, humidity and gap.
What is the best sealant for a water pump gasket?
One of the best choices for water pump sealant is Xtreme Gasket from Silicone Depot. With a temperature range of up to 650°F, this professional-grade silicone sealant can be used to seal all kinds of mechanical components, including water pumps.
Should I use Permatex on a water pump gasket?
It helps hold the gasket onto the removed component on future removal as well where it's usually easier to clean. I used some of the permatex water pump specific sealant when I did the water pump on my Subaru. The forum guys suggest a thin coating on both sides of the paper gasket. It's worked well for ~40k miles.
Do you need to use sealant to install a water pump?
A common installation mistake is to use silicone or sealant on the seal between the water pump and engine block. This can cause these substances to get into the pump impeller and damage its seals. Always follow the installation instructions supplied with the pump.