08 Toyota Highlander 3.5l Intermittent Engine Rattle on Startup

Joel Diagnostician California Posted   Edited  
2008 Toyota Highlander 3.5L (2GRFE) 5-spd (U151E)
Ratlle On Start Up

We have this customer dealing with this issues for a while the highlander has 80 k only. Sometimes in the morning at first startup, the engine makes a rattle noise that last for about 2 seconds, there are no DTC present all readiness monitor completed. It was hard to duplicate the conditions in the shop as it took about 3 days of multiple trys and finally it did. I scope tested cam and crank and oil pressure on channel D, with the noisy pv350 transducer.

First, I will apologized for the photos as they have some words in Spanish because I opened a thread before with them on Spanish forum, however I can not edit them to clear that.

I was thinking may be the chain was making rattle because of timing chain tensioner loosing pressure I was expecting to see it to be move shifting comparing cam and crank during rattle present , but it did not What I found is the delay in oil pressure build up , the oil pressure took longer to build and when it did it spike over 100 psi at that moment when out my scales. I think I do not have a picture save of that. 

We checked for TSB’s and there is one, however apparently does not apply to this engine in particular, even the rattle noise is under the same conditions described as the TSB.

Apparently, the Camshaft phaser drain out and cause the rattle according to tsb and fix is to replace cam phaser which is about expensive job with parts and labor. The wear part is it was the case I was thinking this make have cause the cam to shift in relation to ckp signal. But there is a delay in building up oil pressure and when it does it goes very high e immediately that makes me think the oil pump is being building pressure and it is filling up before compressing it.

We were reading comments on identifix of people has performed the tsb and the noise is still present so we got scared since for us is hard to say what is the cause of oil pressure delay is ultimately making the rattle noise. In conclusion, we told the customer the truth of findings and it could be very expensive guess, we recommended to take it to the dealer.

I wanted to open a discussion and learn together from other having this issues before and what test could you have gone different and why or what do you sell in this case.

Thank you for your inputs in advance.